Don’t Blur the Message on Cancer Screening

By |September 14th, 2012

This week the USPSTF renewed its position on ovarian cancer screening. The panel reminded the public that there’s no value in doing blood tests, like measuring the CEA, or having sonograms to evaluate healthy-feeling women for the possibility of ovarian cancer. One problem with the CEA measurement is that it goes up in various conditions; it’s not a specific test. Similarly, abdominal ultrasounds tend to pick up all kinds of blobby images that are rarely ovarian tumors. More often than not, ovarian cancer screening tests lead women to undergo more tests, such as CT scans and even surgery, without any benefit. The CEA tests and ultrasounds rarely “catch” ovarian tumors in an early stage.

This information on the lack of effective ovarian cancer screening methods is hardly news. What I hope is that this week’s headlines and editorials don’t add to the blurriness of the public’s perception of cancer screening – that people might think it’s a bad thing all around. The details matter. For some cancers, screening the general population – if it’s done right – can save lives and dollars. That’s because for most tumor types, treating advanced, metastatic disease is costlier than treatment of early-stage, curable tumors.

A few words on other cancers and screening –

Prostate cancer screening by PSA testing has never been shown to save lives. Because prostate cancer is unusual in young men and occurs commonly in elderly men, and in those cases tends to be slow-growing, screening’s potential – even if it were safe and effective – to save men’s life-years is limited. What’s different, also – and I think this is where some journalists get the story wrong by omission – is that early treatment of prostate cancer is rarely beneficial. By contrast, early treatment of breast cancer is often life-saving.

Lung cancer screening may be helpful in people at high risk, such as smoking, but one could argue that the CT scans used in those studies – which involve more radiation exposure than do mammograms, besides that they’re more costly – need a higher threshold of benefit to justify their use.

Colon cancer screening has been shown to save lives. For this tumor type, I think the issue is whether it’s worth doing colonoscopy in everyone over the age of 50, periodically, or better to test everyone for tiny amounts of blood (or, in the future, cancerous DNA markers) in the stool. Checking for occult blood in stood samples is a simple and perfectly safe method of getting a little bit of information about the probability of someone having a polyp or frank malignancy in the gut. If people who want to be screened for colon cancer would reliably take a sampling, it’s possible they might safely skip colonoscopy if there’s no evidence for bleeding or other signs of disease.

As for cervical cancer screening, that has definitely been an advance. Pap smears and other liquid cytology methods, now, perhaps HPV testing, have successfully countered this disease. Years ago, women would present, typically in their 30s, 40s or 50s, with large cancers pushing into the body of the uterus and lower abdomen. These were rarely curable. Rather than a scrape, or slightly bigger procedure in a gynecologist’s office, the women needed hysterectomies and radiation to the pelvis, which caused problems down the road if they were lucky and survived. In communities where young women get gynecological care now, we rarely see advanced cases of cervical cancer. For this disease, the question now is in fine-tuning the frequency of screening and understanding how HPV tests can inform or supplement the Pap smear.

As for mammography in breast cancer screening, please don’t get me wrong. I am not fixed in my position that it’s worthwhile and should be performed every other year in most women over the age of 40 until they reach the age of 70 or so, depending on their wishes and overall health. Rather, I acknowledge it’s far from a perfect screening tool, and I genuinely hope that in the future we’ll prevent breast cancer entirely or at least find a better, safer way to detect it early on. But until that happens, for the time being, mammography is a well-established, routine procedure that is the best we’ve got to prevent tens of thousands of middle-aged women from dying every year in the U.S. from metastatic BC.

I generally ascribe to the “less is more” school of medicine. But that doesn’t mean we should ignore early-stage breast tumors, especially when they occur in young-ish women. Rather, it means that we should treat what cancers we do find carefully and conservatively, with the least therapy needed to raise a woman’s chances of leading a normal, healthy and full life.

All for now,

ES

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A Closer Look at the Details on Mammography, in Between the Lines

By |July 26th, 2012

Recently I wrote a review of Between the Lines, a helpful handbook on bio-medical statistics authored by an acquaintance and colleague, Dr. Marya Zilberberg. In that post, I mentioned my concern about some of the assumptions and statements on mammography. One thing I liked the book, abstractly, is the author’s efforts to streamline the discussion so that the reader can follow the concepts. But simplification and rounding numbers, “for ease of presentation” (p. 29) can mess up facts, significantly in ways that some primary care doctors and journalists might not appreciate. And so I offer what I hope is a clarification, or at least an extension of my colleague’s work, for purposes of helping women understand the potential benefits and risks of mammography.

In the section on mammography (pp. 28-31), the author rounds down the incidence of breast cancer in women between the ages of 40 and 50 years, from “1 in 70” (1.43%) to “1 in 100” (1%). As any marketing professional might remind us, this small change represents a 30% drop (0.43/1.43) in the rate of breast cancer in women of that age group. This difference – of 30%, or 43%, depending on how you look at it – will factor into any calculation of the false positive (FP) rate and the positive predictive value (PPV) of the test.

For women ages 40-49 Have breast cancer Don’t have breast cancer
If estimate 1 in 100, 1.0 % 100 9,900
If estimate 1 in 70, 1.43 % 143 9,857

Keep in mind that these same, proportional difference would apply to any BC screening considerations – in terms of the number of women affected, the potential benefits and costs, for the 22,996,493 women between the ages of 40 and 49 counted in the 2010 U.S. Census,

My colleague estimates, fairly for this younger age group of women (who are relatively disposed to fast-growing tumors), that the screening technology (mammography) only picks up 80% of cases; 20% go undetected. In other words – the test is 80% sensitive; the false negative, FN, rate is 20%. In this same section, she considers that the FP rate as 10%. Let’s accept this (unacceptably high) FP rate for now, for the sake of discussion.

As considered in Between the Lines:

If FP rate is 10%, prevalence 1 in 100 Really have BC Don’t have BC Total
Mammography + 80 990 1,070
Mammography - 20 8,910 8,930
Total 100 9,900 10,000

But the above numbers aren’t valid, because the disease affects over 1 in 70 women in this age bracket. Here’s the same table with a prevalence of 1 in 70 women with BC:

If FP rate is 10%, prevalence 1 in 70 Really have BC Don’t have BC Total
Mammography + 114 986 1,100
Mammography - 29 8,871 8,900
Total 143 9,857 10,000

In this closer approximation to reality, the number of true positives is 114, and false positives 986, among 1,100 abnormal screening results. Now, the PPV of an abnormal mammogram is 114/ (114+986) = 10.4%. So the main statistical point – apart from the particulars of this discussion –  is that a seemingly slight rounding down can have a big impact on a test’s calculated and perceived value. By adjusting the BC rate to its prevalence of approximately 1 in 70 women between 40 and 49 years, we’ve raised the PPV from 7.5% to 10.4%.

Here I must admit that I, too, have rounded, although I did so conservatively very slightly. I adopted a 1 in 70 approximation (1.43%) instead of 1 in 69 (1.45%), as indicated on the NCI website. If we repeat the table and figures using a 1 in 69 or 1.45% prevalence rate and 6% FPS, the PPV rises a tad, to 10.5%.

Now, we might insert a different perspective: What if the false positive rate were 6%, as has been observed among sub-specialist radiologists who work mainly in breast cancer screening?

If FP rate is 6%, prevalence 1 in 70 Really have BC Don’t have BC Total
Mammography + 114 591 705
Mammography - 29 9266 9,295
Total 143 9,857 10,000

As you can see, if we use a FP rate of 6% in our calculations, the total number of FPs drops to 591 among 10,000 women screened. In this better-case scenario, the PPV of the test would = 114/ (114+591) =16%. Still, that’s not great – and I’d argue that public health officials, insurers and patients should be pushing for FP rates closer to 2 or 3% – but that’s irrelevant to my colleague’s point and her generally instructive work.

My second concern has to do with language, and making the consequences of false positives seem worse than they really are. On page 29, the author writes: “ So, going back to the 10,000 women being screened, of 9,900 who do NOT have cancer… 10%, or 990 individuals will still be diagnosed as having cancer.” The fact is, the overwhelming majority of women with positive mammograms won’t receive a cancer diagnosis. Rather, they’ll be told they have “an abnormal result, or a finding that suggests the possibility of cancer and needs further evaluation,” or something along those lines. It would be unusual in practice to jump from a positive mammogram straight to a breast cancer diagnosis. There are steps between, and every patient and journalist should be aware of those.


Finally, if I were to write what I really think, apart from and beyond Between the Lines – I’d suggest the FP rate should be no higher than 2 or 3% in 2012. This is entirely feasible using extant technology, if we were to change just two aspects of mammography practice in the U.S. First, require that all mammograms be performed by breast radiologists who get extra training and focus in their daily work almost exclusively on breast imaging. Second, make sonograms – which, together with mammograms, enhance the specificity of BC screening in women with dense breasts– universally available to supplement the radiologists’ evaluations of abnormal mammograms and dense breasts in younger women.

By implementing these two changes, essentially supporting the practice of sub-specialists in breast radiology, we could significantly lower the FP rate in breast cancer screening. The “costs” of those remaining FPs could be minimized by judicious use of sonograms, needle biopsies and other measures to reduce unnecessary surgery and over-treatment. Over the long haul, we need to educate doctors not to over-treat early stage disease, but that goes far beyond this post and any one woman’s analysis of mammography’s effectiveness.

All for now,
ES

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What Does it Mean if Primary Care Doctors Get the Answers Wrong About Screening Stats?

By |March 15th, 2012

Last week the Annals of Internal Medicine published a new report on how doctors (don’t) understand cancer screening stats. This unusual paper reveals that some primary care physicians – a majority of those who completed a survey – don’t really get the numbers on cancer incidence, 5-year survival and mortality.

An accompanying editorial by Dr. Virginia Moyer, a Professor of Pediatrics and current Chair of the USPSTF, drives two messages in her title, What We Don’t Know Can Hurt Our Patients: Physician Innumeracy and Overuse of Screening Tests. Dr. Moyer is right, to a point. Because if doctors who counsel patients on screening don’t know what they’re speaking of, they may provide misinformation and cause harm. But she overstates the study’s implications by emphasizing the “overuse of screening tests.”

The report shows, plainly and painfully, that too many doctors are confused and even ignorant of some statistical concepts. Nothing more, nothing less. The new findings have no bearing on whether or not cancer screening is cost-effective or life-saving.

What the study does suggest is that med school math requirements should be upped and rigorous, counter to the trend. And that we should do a better job educating students and reminding doctors about relevant concepts including lead-time bias, overdiagnosis and – as highlighted in two valuable blogs just yesterday, NPR Shots and Reporting on Health Antidote – the Number Needed to Treat, or NNT.

The Annals paper has yielded at least two unfortunate outcomes. One, which there’s no way to get around, is the clear admission of doctors’ confusion. In the long term, this may be a good thing, like admitting a medical error and then having QA improve as a consequence. But meanwhile some doctors at their office desks and lecterns don’t realize what they don’t know, and there’s no clear remedy in sight.

Dr. Moyer, in her editorial, writes that medical journal editors should carefully monitor reports to ensure that results aren’t likely misinterpreted. She says, in just one half-sentence, that medical educators should improve teaching on this topic. And then she directs the task of stats-ed to media and journalists, who, she advises, might follow the lead of the “watchdog” HealthNewsReview. I don’t see that as a solution, although I agree that journalists should know as much as possible about statistics and limits of data about which they report.

The main problem elucidated in this article is a failure in medical education. The cat’s out of the bag now. The WSJ Heath Blog covered the story. Most doctors are baffled, says Fox News. On its home page, the Dartmouth Institute for Health Policy & Clinical Practice links to a Reuters article that’s landed on the NIH/NLM-sponsored MedlinePlus (accessed 3/15/12). This embarrassment  further compromises individuals’ confidence in doctors they would and sometimes need rely on.

We lie, we cheat, we steal, we are confused… What else can doctors do wrong?

The second, and I think unnecessary, problematic outcome of this report is that it’s been used to argue against cancer screening. In the editorial Dr. Moyer indulges an ill-supported statement:

…several analyses have demonstrated that the vast majority of women with screen-detected breast cancer have not had their lives saved by screening, but rather have been diagnosed early with no change in outcome or have been overdiagnosed.

The problem of overdiagnosis, which comes up a lot in the paper, is over-emphasized, at least as it relates to breast cancer, colon cancer and some other tumors. I  have never seen a case of vanishing invasive breast cancer. In younger women, low-grade invasive tumors are relatively rare. So overdiagnosis isn’t applicable in BC, at least for women who are not elderly.

In the second paragraph Dr. Moyer outlines, in an unusual mode for the Annals, a cabal-like screening lobby:

 …powerful nonmedical forces may also lead to enthusiasm for screening, including financial interests from companies that make tests or testing equipment or sell products to treat the conditions diagnosed and more subtle financial pressures from the clinicians whose daily work is to diagnose or treat a condition. If fewer people are diagnosed with a disease, advocacy groups stand to lose contributions and academics who study the disease may lose funding. Politicians may wish to appear responsive to powerful special interests…

While she may be right, that there are some influential and self-serving interests and corporations who push aggressively, and maybe too aggressively for cancer screening, it may also be that some forms of cancer screening are indeed life-saving tools that should be valued by our society. I think, also, that she goes too far in insinuating that major advocacy groups push for screening because they stand to lose funding.

I’ve met many cancer agency workers, some founders, some full-time, paid and volunteer helpers – with varied priorities and goals – and I honestly believe that each and every one of those individuals hopes that the problem of cancer killing so many non-elderly individuals in our society will go away. It’s beyond reason to suggest there’s a hidden agenda at any of the major cancer agencies to “keep cancer going.” There are plenty of other worthy causes to which they might give their time and other resources, like education, to name one.

Which leads me back to the original paper, on doctors’ limited knowledge –

As I read the original paper the first time, I considered what would happen if you tested 412 practicing primary care physicians about hepatitis C screening, strains, and whether or not there’s a benefit to early detection and treatment of that common and sometimes pathologic virus, or about the use of aspirin in adults with high blood pressure and other risk factors for heart disease, or about the risks and benefits of drugs that lower cholesterol.

It seems highly unlikely that physicians’ uncertainty is limited to conceptual aspects of cancer screening stats. Knowing that, you’d have to wonder why the authors did this research, and why the editorial pushes so hard the message of over-screening.

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New Studies on Colon Cancer Screening by Colonoscopy and Fecal Blood Testing

By |February 28th, 2012

Last week the NEJM published two major papers on screening for colon and rectal cancer. The most notable finding supports that colonoscopy – when done properly and not necessarily often – saves lives.

The NCI estimates that doctors will find over 103,000 colon and 40,000 rectal cancers, and the number of deaths will exceed 51,000 this year in the U.S. According to the ACS, colorectal cancer ranks third as a cause of cancer mortality in men and in women. In light of these numbers, the potential for screening to reduce deaths and costs of treating people with advanced disease is great.

Both analyses are unfortunately – almost dauntingly – complicated. An accompanying editorial, by Drs. M. Bretthauer and M. Kalager lends some perspective.

colon adenoma pathology, H&E stain, (Wiki Commons: "Nephron")

The first report comes from a group of researchers led by Ann Zauber, PhD, a biostatistician at MSKCC. This team examined long-term outcomes among 2602 adults who had adenomatous polyps removed between 1980 and 1990, followed by colonoscopy recommended at varying intervals in a trial. With a median follow-up of 15.8 years, there were only 12 deaths from colon cancer in the study population – essentially half the number expected by comparison with SEER data.

The main limitations I see in this report are two. First, what might be considered a good thing – the high compliance rate: 81% of those with adenomas underwent some follow-up colonoscopy. And second – along a similar vein – that the colonoscopies were performed by highly-trained physicians at academic centers in a trial that mandated a certain degree of thoroughness and quality. Some criticism of the work is that the findings won’t translate to the community at large, as mentioned in the editorial and in the paper itself. That’s because some “real world” gastroenterologists don’t perform the procedure so carefully. Apart from the trial, many people are genuinely hesitant about having colonoscopy out of concern about its unpleasantness and also costs. Compliance with colonoscopy recommendations runs low.

These are valid concerns. But they don’t abrogate the value of the procedure. Rather, they point to the need for rigorous training of doctors who do colonoscopy, for close monitoring of facilities where it’s done (and in path labs, where the specimens are evaluated), and for insurance or a national health plan to enable patients, if they choose, to have this potentially life-saving screening test covered.

The second study, from a group in Spain, examined the relative merits of checking stool samples for blood every two years vs. colonoscopy every ten years in over 50,000 people. The preliminary finding – after just one “round” of colonoscopy in those assigned to that trial arm, is that a higher proportion complied with fecal blood testing than with colonoscopy. Among those who underwent colonoscopy, cancers and adenomas were found in a greater fraction. But the absolute number of cancers detected was essentially the same in each group, because more people assigned to fecal screening completed the task.

My take from these reports, combined, is that periodic colonoscopy has the potential to halve the number of deaths from colon cancer in the general population. But it’s an unpleasant, invasive and expensive test that does carry some risks. The quality of the test – both in terms of its thoroughness and risk of complication – would depend, in part, on the training and experience of the doctor who performs the test. So, as with mammography, I favor heavy regulation and careful certification of physicians who perform these procedures.

As to how colonoscopy relates to fecal blood testing as a screening method at the population level, and the optimal start and frequency of either test, those remain uncertain. Dr. Zauber, it turns out, heads the NCI-funded National Colonoscopy Study. This ongoing work will, hopefully, shed light on how testing for blood in stool samples compares with colonoscopy in colon cancer screening and, ultimately, costs and mortality from late-stage disease.

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Cervical Cancer Screening Update: on Pap Smears, Liquid-based Cytology and HPV

By |November 29th, 2011

The latest issue of the Annals of Internal Medicine contains 2 noteworthy papers on cervical cancer screening. The first, a systematic review of studies commissioned by the USPSTF, looked at 3 methods for evaluating abnormalities in women over 30 years:

high-grade cervical cell dysplasia (Dr. E. Uthman, Wikimedia Commons)

1. Conventional cytology (as in a Pap smear; the cervix is scraped and cells splayed onto a microscope slide for examination);

2. Liquid-based cytology (for LBC, the NHS explains: the sample is taken as for a Pap test, but the tip of the collection spatula is inserted into fluid rather than applied to slides. The fluid is sent to the path lab for analysis);

3. Testing for high-risk HPV (human papillomavirus). Currently 3 tests have been approved by the FDA in women with atypical cervical cells or for cervical cancer risk assessment in women over the age of 30: Digene Hybrid Capture 2 (manufactured by Quiagen), Cobas 4800 HPV (Roche) and Cervista HR HPV (Hologic); another Roche Diagnostics assay, Amplicor HPV, awaits approval.

These HPV assays use distinct methods to assess DNA of various HPV strains.

There’s a lot of jargon here, and I have to admit some of this was new to me despite my nearly-due diligence as a patient at the gynecologist’s office and my familiarity as an oncologist with the staging, clinical manifestations and treatment of cervical cancer. Who knew so many decisions were made during a routine pelvic exam about which manner of screening?

The main points I took away from this paper:

1. Liquid-based cytology is similar to conventional Pap smear cytology for detecting high-grade dysplasia (abnormal cells) and cervical cancer.

2. It seems that at some medical centers, and possibly overall, there’s a lower proportion of inadequate cell specimens when practitioners skip the slides and use the liquid method. This means that fewer women need be called back for another procedure.

3. Finding HPV sequences in the cervix yields many false positives, in terms of malignancy.

The researchers conclude that further studies are needed to sort out how HPV testing can improve or supplement cervical cancer screening. The main limitation is that many young women are infected with potentially cancer-causing strains of HPV, but most don’t get cervical cancer. When cervical cancer does develop that’s usually later on, a decade or longer after the relevant viral infection.

The second Annals article, a helpful narrative review, considers the practical implications of the above findings. The authors state that over 40 types of HPV can infect the cervix. They review that progression to cancer occurs along these 4 steps: HPV transmission, acute infection, persistent infection causing precancerous changes and eventually, in a subset of those infected, invasive cervical cancer.

Figure 1 is remarkably clear:

Prevalence of high-risk HPV and incident cases of cervical cancer in the U.S., 2003–2005. Surveillance Epidemiology and End Results (SEER) data for incident cases among females aged 15 to 19 years and 50 to 64 years.

The graph shows that the prevalence of HPV infection is highest among teens and women in their early 20s, and decreases in older women. By contrast, the incidence of cervical cancer rises steadily in women over 30 years and remains elevated among women in their 40s. The authors show, separately, that the rate of cervical cancer in older women is low.

The central point is that high-risk HPV infection and associated inflammation of the cervix are common in young women, but cervical cancer is rare among those under 30 years. The investigators conclude that cervical cancer screening in women younger than 20 years may be harmful. They also state that evidence supports discontinuation of cervical cancer screening in most women who are over 65 years old.

Two asides on this otherwise non-bloggy topic -

It’s great that the Annals provides the full text of these papers open-access, free of charge to the public.

Amazing how well-accepted is the concept of some viruses causing cancer, today. This was a heretical idea 25 years ago in academic medicine; now it’s dogma.

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3 Differences between Prostate and Breast Cancer Screening

By |October 12th, 2011

Days ago, the USPSTF issued a new draft for its recommendations on routine PSA measurements in asymptomatic men. The panel’s report is published in the Annals of Internal Medicine. The main findings are two: first, the absence of evidence that routine PSA testing prolongs men’s lives, and second, that PSA evaluation may, on balance, cause more harm than good.

Not surprisingly, there’s been considerable coverage of this by the media, and some controversy. For decades, many men have had their PSA checked, knowingly or not, by their physicians. The PSA test  measures the level of Prostate Specific Antigen, a protein produced and sometimes secreted by prostate cells, normal, inflamed or malignant, into the bloodstream.

As an oncologist, I don’t find the panel’s recommendations surprising. There’s never been strong data to support the hypothesis that routine PSA testing reduces mortality for men in any age group. Prostate cancer is often indolent, a slow-growing kind of tumor for which a “watch and wait” approach may be best, especially when it occurs in elderly men who are most likely, even in the absence of treatment, to die of another cause. The complication rate of prostate surgery is fairly high, although this “cost” of screening likely varies, depending on the skill of the surgeon. Still, and understandably, there are men who swear by this measurement, whose lives have been, in some cases, saved by early detection of a high-grade tumor upon screening.

For today, I’d like to consider some key differences between breast and prostate cancers, and the potential value of screening:

1. Breast cancer tends to affect younger patients than prostate cancer.

Based on SEER data, the median age of a breast cancer diagnosis in the U.S. is 61 years. The median age of death from breast cancer is 68 years. For prostate cancer, the SEER data show a median age of 67 years at diagnosis, and for death from prostate cancer, 80 years.

So the potential number of life-years saved by early detection and intervention is, on average, greater for breast cancer than for prostate cancer.

2. Screening for breast cancer has improved over the past 25 years.

Because the blood test for PSA hasn’t changed much in decades, it’s reasonable to consider studies and long-term survival curves based on data going back to the 1980s.

Mammography, by contrast, is much safer and better than it was 25 years ago, for various reasons: increased regulation of mammography facilities (more care with the procedure, better training and credentialing of technicians) according to the FDA’s Mammography Quality Standard Acts Program ; development of ultrasound methods to supplement mammograms in case of suspicious lesions (lessens the false positive rate overall); the advent of digital technology (lessens the false positive rate in younger women and others with dense breasts); more breast radiology specialists (expertise).

The data reviewed by the USPSTF in issuing their 2009 recommendations for BC screening were decades old, and, as I’ve considered previously, irrelevant to modern medical practices. A recent article in the NEJM points to the problem of the panel’s reliance on the Age trial for women in their 40s. That trial involved the obsolete method of single-view mammography.

3. Mammography involves a woman’s consent (in the absence of dementia – a separate ethical issue).

A woman knows if she’s getting a mammogram. She may not ask sufficient questions of her doctor, or her doctor may not answer them well, but in the end she does or doesn’t enter into a radiology room, volitionally. She decides to get screened, or not. She can choose to have a mammogram every year, or every other year, or not at all.

There’s no ethical problem, as reported for some men, of patients learning they have an abnormal PSA, after blood was drawn indiscriminately, without their knowing the test was being performed.

This perspective might, and should, later extend to consider additional differences between these two kinds of malignancies (each of which is really a group of cancer subtypes), a fuller discussion of the impact of treatment on survival for each type, and the relative risks of screening due to differential complication rates of biopsies and other procedures.

To be clear, there’s no perfect screening test for either cancer type. Far from it. But the merits and risks of each procedure should be weighed separately, and with care.

All for today.

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A Call for Clarity in Cancer Screening Discussions

By |October 7th, 2011

Today’s cancer news is about screening for prostate cancer. The U.S. Preventive Services Task Force will advise that men should not be screened by a PSA (prostate specific antigen) blood test. The new recommendations will apply to asymptomatic men in all age groups.

I happen to agree with the task force’s position on this, but the point I’d like to make is obvious but too-often missed by the press and others who consider cancer screening:

Prostate cancer is not the same as breast cancer. Rather, each is a distinct set of related diseases with varied prognoses and treatment options.

For any screening method, the potential benefit of detecting cancer early depends on the specific tumor type, the accuracy of the test, and the likelihood that treatment will be effective and confer a net benefit over risks. A key to understanding the screening debate(s) is not to conflate data for distinct cancer forms in a discussion of the value of screening for a particular cancer type.

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Stepping Back, and Thinking Forward to October

By |September 23rd, 2010

Before jumping into the raring-to-go, already re-sparked debate on the value of breast cancer screening, or not, I thought I’d step back today and consider the background of what I won’t call the “mammography wars.”

So here’s the first point on this subject: happily, it’s not a war. This is about medical progress, or lack of progress, and what may or may not spare women morbidity (what doctors and stats types call illness) and mortality (death). This is not a battle by any sane measure.

The discussion should be civil and fair, ideally without assumptions and bias. (Of course it’s impossible for me to be unbiased on this subject – I am a trained oncologist, I’ve treated women with breast cancer who responded to chemotherapy drugs and witnessed their subsequent well-being, and I’ve seen women with metastatic breast cancer who died with disease eating through their bones and brains. And I had breast cancer, and was lucky that mine was found in an early stage. So far am well in that respect, eight years ago next month and counting -)

So I have bias, yes, but my second point is that we all do. Every journalist does, whether or not they’re up front about their life-experiences and community background, and so does every medical researcher and public health official who authors a paper and is not a robot. We delineate stories, analyze and represent data based on points we want to make and, in some medical journals – even for some trials that aren’t funded by drug companies – publish to serve academic, career or even what we think are idealistic, cost-saving, pain or procedure-sparing often high-minded goals.

Data can be very tricky to sort out and among.

The problems with mammography studies, as partly-detailed in the current NEJM paper, is that it’s considered impossible to do a controlled, randomized trial in which half of the women undergo screening and half don’t. (I might argue this assumption; now, that so many women and doctors are questioning the merit of mammography, maybe we could do a truly randomized trial involving a few thousand women in the U.S.) This issue relates to the important topic of ethics and real-life dilemmas oncologists face when they set up studies for evaluation or treatment of humans some of whom are likely to die.

But before we delve into the details of this study, and next month (October), what I hope is that we’ll keep some facts in mind:

The National Cancer Institute estimates that 40,000 women will die of breast cancer this year in the U.S. There’s been dramatic progress in how we manage this once-dreaded condition: prior to 1926, fewer than 20 percent of women survived for 5 years after diagnosis. By 1950, the overall 5-year survival rate among Caucasian women with breast cancer was 60 percent. Now, the overall 5-year survival rate is around 91 percent.

A question central to today’s discussion – which does at least acknowledge the decline in breast cancer mortality – is the extent to which mammography is responsible for this trend, as opposed to other factors such as increased awareness about cancer, better cancer treatments and other variables.

What concerns me is the tone of the debate on mammography, that it shouldn’t subtly or not-so-subtly, denigrate women’s valid concerns about their health. The quote with which today’s front-page story ends is this: “I think we have to respect what women want to do.” The way the story is framed insinuates that a decision to undergo mammography is based on something other than reason.

To be clear: this is not about what women want. It’s not about emotional turmoil, comfort, stress or people’s feelings. It’s about the efficacy of state-of-the art mammograms and whether or not those, when taken by skilled, well-trained radiologists in carefully-regulated modern facilities save women’s lives, at a reasonable cost (however we might calculate that) and reduce illness by detecting breast cancer in its early stages.

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The New Alzheimer’s Plaque Test (and early breast cancer detection)

By |June 24th, 2010

Alzheimer’s is, unfortunately, an incurable disease. On the front page of today’s print edition of the New York Times, Gina Kolata reports on a new test that would enable doctors to image the characteristic plaques in the brain and, thereby, facilitate the diagnosis in people who are wondering if they have this condition. The news article includes pretty images, front and center in my browser window.

The discussion centers on a not-yet-FDA-reviewed test promoted by a biotech company, Avid Radiopharmaceuticals (Philadelphia, PA). The experimental method depends on using PET scans (radiation dose estimate 14.1 mSv, Health Physics Society fact sheet) using a radioisotope (fluoride-18)-conjugated dye (Avid, in collaboration with Bayer and GE).

Among my hundred questions about this enterprise – notwithstanding the ethics of performing clinical trials in hospice patients, as is related in the Times article – is this: does the dye harm the kidneys? (No mention in the article.)

As for how much it costs, that’s not said either. Because Alzheimer’s is a fairly common disease and memory loss an even commoner condition, the potential demand for this marketable diagnostic method might be great.

What are we thinking?

Unlike Alzheimer’s, breast cancer is a highly-treatable disease. The cure rate for cases detected in stage I is over 95 percent, and for stage II it’s well-above 85 percent. These results apply to all women with breast cancer, including those in their forties and fifties.

Metastatic breast cancer remains incurable as I write this morning. Finding it early is crucial. About Alzheimer’s, I’m not so sure.

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Another Erroneous Report on Breast Cancer Screening by Mammography

By |March 26th, 2010

This week delivered another piece on the non-value of breast cancer screening by mammography. The report, published in the British Medical Journal (BMJ), would be minor except that it may add to the growing heap of erroneous data on the topic.

Disclosure: I’m a board-certified oncologist, I’ve had breast cancer and this issue matters to me more than it otherwise might. I’m biased, yes for sure. It’s also true that my position is particularly informed.

The new study is limited and confusing. My initial take was that it wasn’t post-worthy. But since it’s out there, mentioned and even deemed important by some friends and colleagues, I thought I should explain why I think it’s wrong:

What the authors tried to do was analyze trends in breast cancer mortality in relation to mammography’s availability in distinct regions of Denmark over several decades. Using Poisson regression, a form of statistical analysis, they looked for a correlation and found none. They concluded that they couldn’t detect a benefit of screening mammograms among Danish women who might benefit (see below).

Map of Denmark, CIA World Factbook (Wikimedia Commons)

Here’s what I think are the two most serious flaws in this observational study:

1. The investigators divided Denmark into two groups for analysis: one defined as the “screened area” comprises Copenhagen, where mammography’s been available since 1991, and Funen County, where it’s been available since 1993; and the “non-screened” area representing approximately 80% of the population – “the rest of the country.”

The problem is that Copenhagen is Denmark’s capital and Funen, the other main “screened” region, contains Odense, the country’s third largest city. It’s not reasonable to compare changes in breast cancer survival, with or without screening, between women living in mainly urban and mainly rural areas, as these regions can differ at baseline in education, diet, alcohol use, cigarette use, pollution levels and other potentially confounding variables. Also, the quality of medical care in itself can vary between urban and rural districts. Differences in availability of primary care, surgical and other supportive services can influence survival trends independently of breast cancer screening.

2. For purposes of their study, the authors split the Danish women into three age brackets: aged 35-54, “women who were too young to benefit from screening”; aged 55- 74, “women who could benefit from screening”; and 75 – 84, “older age groups.” This assumption, that women under the age of 55 can’t benefit from mammography, introduces circular reasoning into the study, right from the start.

—-

I’m not sure why the BMJ published this paper. I’m concerned, really, that it’s agenda-driven work. The authors state, up front, that their findings contradict those of 2005 report drawn from a distinct but overlapping data set, that mammography was associated with a 25% reduction in breast cancer deaths in Denmark.

What’s curious is that the researchers do in the end identify a possible small cancer mortality reduction among the younger women. In their words:

…We also note that in the age group too young to have benefited from screening, women experienced proportionately larger reductions in breast cancer mortality after screening was introduced than did those that could have benefited from screening.

This non-logic reflects the investigators’ erroneous presumption that there cannot be an advantage in women aged 35 – 55.

You can go ahead and examine this paper directly if you like. A true advantage of the BMJ is its open-access; it provides full text freely upon registration.

My take-home message: this flawed publication should not be used to support the contention that breast cancer screening by mammography is ineffective. Nor does it elucidate much about what’s happening with mammograms and breast cancer survival trends in Denmark.

What it does reveal, if anything, is how different researchers using similar but non-identical data sets can come up with conflicting results if they want to.

Finally, I’ll remind my readers that the mortality rate among women with breast cancer has declined dramatically in the U.S. since 1990 and in Copenhagen, when mammography became prevalent in those places. The studies published in November, 2009 in the Annals of Internal Medicine, on which the new U.S. Preventive Services Task Force recommendations were based, are limited by reasons I’ve outlined here and elsewhere.

Addendum (3/28/08) : typo correction, some links and map added on March 28 by ES.

Regret: I wish I could find a better public domain map source.

Request: if any readers happen to know something about Danish epidemiology, and how Copenhagen and Funen counties do or don’t differ from the rest of Denmark, please chime in!

Related Posts:

Peter Sings Colonoscopy

By |March 17th, 2010

Hi Readers,

This new form of medical information outreach outweighed any other contenders for today’s post:

“When I had my colonoscopy I had a question on my mind.

Do we all look the same when the doctor sees us from behind?

Then I had the answer…

Peter Yarrow, starting The Colonoscopy Song

Am I pro- or con- colonoscopy for routine screening, you might wonder. Well, that depends.

Am I pro- or con- famous singers and other celebrities extolling the benefits of particular medical interventions? Well, that depends, too.

But I’m sure I prefer “Puff the Magic Dragon.” Also “Leaving on a Jet Plane” fills me with imperfect memories of 6th grade. (I don’t know much about the history of this song, but there is an older, grainier and harder-to-hear version on YouTube dating to March, 2008.)

Thanks Peter, for this unique verbalization of what some doctors might otherwise convey. Glad to see you singing, aging, smiling about something.

The CDC confirms that March is national colorectal cancer awareness month (NCCAM).

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A Visit With My Oncologist

By |January 28th, 2010

Today I visited my oncologist for a checkup.

Waiting to see her, I sat in a floral fabric chair by a matching wood veneer coffee table strewn with worn magazines – Architectural Digest, Better Homes and Gardens and some old Time issues – I couldn’t help but think of how I was feeling seven years ago.

Then I was anxiously waiting to know my blood counts – the white cells, red cells and platelets – to see if they were sufficient for my scheduled chemotherapy.

That January, my white blood cells were so low that some doctors thought I should enter the hospital for IV antibiotics. (I declined.) My mouth was so full of sores I could hardly speak or eat. My hair was gone and I wore a strange wig. My right arm was broken (yes, I’m right-handed) so I couldn’t write or type. I was pale, weak with anemia and covered with bruises.

Chemo-brain, which I’d never learned about in med school, was just starting to set in. Before then, I’d always taken pride in keeping up with medical and science journals. But I could barely muster the energy to take a glance at those heavyweights. Even regular magazines appeared fuzzy, a scary symptom for an oncologist who knows too well that breast cancer cells can spread upstairs.

I wanted my next treatment. I wanted to get it over with, to put the breast cancer behind me.

After a while my oncologist stepped out into the waiting area and guided me to the hall by her office. “The cells are low,” she said. “We’ll have to wait another week, that’s all.”

I knew she was right. But a week seemed like a lifetime to me then.

I understood that giving chemotherapy suppresses the bone marrow, the body cavity where blood cells form. If my white cells dropped any lower, I’d be at serious risk for bacteria in the blood or invasive yeast in my mouth and throat. If the treatment reduced the red cell-forming elements in the marrow, I’d become more anemic. Already I was on a medication that affected the function of platelets, the blood-clotting cells. If the platelets fell further, I’d be at greater risk for bleeding.

I had no choice but to wait. So I did. The next week I got my treatment, and we were back on track, at least for a while.

Today, sitting in a similar chair, I calmly read the arts section of the newspaper and started working on the crossword. I’d tucked the New England Journal of Medicine into my bag, thinking I should read that, but it didn’t seem right. I wanted to remember what it’s like to be a patient who doesn’t know if she’ll make it through.

Several of my friends, mainly women, are affected now by cancer that’s spread. They go to see their oncologists regularly, and sit and wait for their blood counts, and sometimes get their treatments. Most hold undeniably upbeat, positive attitudes. But the reality is tough-going, day-to-day and month after month, with no easy end in sight.

How much easier it is to look back on a situation – a tumor – that was removed in an early stage. My cancer treatment wasn’t easy, but I don’t regret it for a second.

When my oncologist took me into her office today we chatted for a while and then she examined me.

“Come back next year,” she said.

In my medical storybook, it doesn’t get much better than that.

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Proposed Model for Evaluating False Positives in Screening Mammography

By |December 30th, 2009

First, a definition* -

False positives happen in screening mammography when the images suggest the presence of a malignancy in a woman who doesn’t have cancer in her breast.

Here’s my proposed model –

Categories of False Positives in Screening Mammograms

False positives can arise during any of three conceptual segments of the testing process:

1. False positives occur during the test itself.

This happens when a radiologist inspects a film or digital image and labels the result as abnormal, but no cancer is present. This sort of problem is interpretive.

A common scenario goes like this – a spot in a mammography image suggests the presence of a possible tumor and the radiologist correctly notes that abnormality; later on, a doctor determines by sonogram, biopsy or another method that there is no malignancy in the breast.

(Other, uncommon problems in this category would include faulty equipment that reduce image quality, mislabeling or accidental switching of films; in principle, these kinds of errors should be non-events.)

2. False positives stem from miscommunication or misunderstanding of test results.

If a clerk accidentally phones the wrong patient and tells her she needs another procedure because the results of her mammogram are abnormal, that call might instigate an untoward, false positive result. If the error is corrected early on, so that affected woman worries only for a period of hours and has difficulty sleeping for one night, she might experience some psychological and/or small financial cost from the matter. But if the mistake isn’t caught until after she’s had a sonogram or MRI, and consulted with a surgeon or another physician, the costs grow.

False positives also arise if a patient misunderstands a test result. An essentially normal mammography report, for example, might mention the appearance of benign calcifications. Upon reading that result, a woman or her husband might become upset, somehow thinking that “benign” means “malignant.” This type of false positive error, based in poor communication and lack of knowledge, can indeed generate extra doctors’ visits, additional imaging tests and, rarely, biopsies to relieve misguided fears.

3. False positives derive from errors or misinterpretation of results upon follow-up testing.

This category of false positives in screening mammography is by far the biggest, hardest to define and most difficult to assess. It includes a range of errors and confusion that can arise after breast sonograms, MRIs and breast biopsies.

3a. false positives in subsequent breast imaging studies such as sonograms and MRIs:

Many women in their forties and early fifties are premenopausal; their estrogen-stimulated breasts tend to be denser than those of older women. Reading their mammograms may be less accurate than for postmenopausal women. For this reason, a doctor may recommend a sonogram or MRI to further evaluate or supplement the mammography images.

These two radiology procedures – sonograms and MRIs – differ and, for the most part, are beyond the scope of this discussion except that they, too, can generate false positive results. A sonogram, for instance, may reveal a worrisome lump that warrants biopsy. MRIs are more expensive and sensitive; these tend to pick up subtle breast irregularities including a relatively high proportion of benign breast lesions.

3b. false positives in breast biopsy:

A breast biopsy is an invasive procedure by which a piece of the gland is removed for examination under the microscope. Sometimes pathologists use newer instruments to evaluate the genetic, protein and other molecular features of cells in the biopsy specimen. Years ago, surgeons did the majority of breast biopsies. Now, skilled radiologists routinely do a smaller procedure, a core needle biopsy, using a local anesthetic and a small albeit sharp instrument that’s inserted through the skin into the breast. Some doctors do a simpler procedure, fine-needle aspiration, by which they remove cells or fluid from the breast using a small needle attached to a syringe.

In principle, a false positive biopsy result would occur only when a pathologist, a physician trained to examine tumors at the cellular and molecular levels, misreads a case, meaning that he or she reports that the cells appear cancerous when they’re not. Fortunately, this is not a frequent issue in breast cancer diagnosis and management.

The real issue about false positives – and what may be the heart of the issue in mammography screening – has to do with how pathologists describe and define some premalignant conditions and low-grade breast tumors. This concern extends well beyond the scope of this tentative outline, but a few key terms should facilitate future discussion:

Lobular Carcinoma in Situ (LCIS) is not considered a malignancy by most oncologists, but rather an abnormality of breast glands that can develop into breast cancer.

Ductal Carcinoma in Situ (DCIS) is a Stage 0 breast tumor – a tiny cancer of breast cells that have not penetrated through the cells lining the ducts of the breast gland.

Indolent or “slow” tumors – The idea is that some breast cancers grow so slowly there’s no need to find or treat these.**

——

*This definition warrants some discussion, to follow in a separate post.

**As a physician and trained oncologist, I am uncomfortable with the published notion of some breast tumors being “so slow” that they needn’t be found or evaluated. I include these tumors only for the sake of completeness regarding theoretical types of false positive results upon screening mammography, as there’s been considerable discussion of these indolent tumors in recent news.

Slow-growing breast tumors are quite rare in young women. In my view, their consideration has no bearing on the screening controversy at it pertains to women in their forties and fifties.

——

As outlined above, the first two categories of false positives seem relatively minor, in that they should be amenable to improvements in quality of mammography facilities and technology; the third category is huge and where lies the money, so to speak.

Clearly there’s more work ahead -

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A Bit More on False Positives, Dec 2009, Part 1

By |December 29th, 2009

The question of false positives in breast cancer screening – why and how these happen, how often these occur, and how much these cost, in physical, psychological and financial terms – remains a puzzle.

A few weeks ago the New York Times Magazine featured a piece on “Mammogram Math” under the heading “The Way We Live Now.” The author, a mathematics professor, argues that the risks and costs of mammography, though incalculable, outweigh the benefits. The paper printed the article along with a subtitle, “Why evidence-based medicine is actually right and scary” and later published three letters including one truncated response by me.

After a hiatus, I’ve rescanned the literature – just to be sure the question hasn’t been resolved in the past few weeks by a much-needed interdisciplinary team of health care policy experts, economists,  statisticians, surgeons, radiologists, oncologists, nurses and for good measure, perhaps a few breast cancer patients and survivors.

There’s little published progress to report, aside from more hype and theoretical numbers such as I offered in a November essay. So I’ve decided to take the analysis a step further by outlining a tentative framework for thinking about false positives in breast cancer screening.

In a separate post, I will outline a proposed outline for categorizing false positives as they relate to mammography. Why bother, you might ask – wouldn’t it be easier to drop the subject?

Make it go away,” sang Sheryl Crow on her radiation sessions.

Instead, I’ll answer as might a physician and board-certified oncologist who happens to be a BC survivor in her 40s:

To determine the damage done to women by screening mammography (as some claim and refer as evidence) we need establish how often false positives lead, in current practice, to additional procedures such as sonograms (fairly often, but the costs are relatively small), MRIs (less standard and more expensive), breast biopsies (scarier, slightly risky and more valued – how else can a pathologist determine if a woman with a breast lesion has cancer and, in the future, what type of therapy is best) or frankly inappropriate treatments such as chemotherapy for a non-cancerous condition (very damaging and the most costly of all putative false positive outcomes).

These numbers matter. They’re essential to the claim that the risks of breast cancer screening outweigh the benefits.

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Legitimate Concerns and Unfortunate Timing on Radiation from C.T. Scanning

By |December 15th, 2009

This week’s cancer news features a study in the current issue of the Archives of Internal Medicine, first reported by Reuters:

CHICAGO (Reuters) – Radiation from CT scans done in 2007 will cause 29,000 cancers and kill nearly 15,000 Americans, researchers said on Monday:

…The findings, published in the Archives of Internal Medicine, add to mounting evidence that Americans are overexposed to radiation from diagnostic tests, especially from a specialized kind of X-ray called a computed tomography, or CT, scan.

The risks of radiation from CT scanning will almost certainly add to the current confusion and concerns about the risks of breast cancer screening.

Mammography differs from CT scanning in several important ways:

1. Mammograms involve much less radiation exposure than CT scans.

According to the American Cancer Society, a typical mammogram uses between 0.1 to 0.2 mSV per image. So even if multiple images are taken of each breast, the total dose remains under 1 mSV.

Another source, the Health Physics Society, estimates a dose of 0.7 mSV per mammogram. So if a woman were to have a screening mammogram every other year between the ages of 40 and 49, she’d receive approximately 3.5 mSV in total from those procedures.

By contrast, a single CT scan involves over a 10-fold greater amount of radiation (such as 8 mSV for a CT of the chest, 10 mSV for a CT of the abdomen) according to the Health Physics Society fact sheet.

2. Mammography is well-regulated by the Food and Drug Administration (FDA) and other agencies.

The Mammography Quality Standards Act (MQSA) requires mammography facilities across the nation to meet uniform quality standards. The law, first passed in October, 1992, requires all mammography facilities to 1) be accredited by an FDA-approved accreditation body, 2) be certified by FDA, or its State, as meeting the standards, 3) undergo an annual MQSA inspection, and 4) prominently display the certificate issued by the agency.

3. Women who undergo screening mammograms can control when and where they get this procedure.

Screening mammograms are elective by nature; a woman can choose an accredited screening facility and, in advance, learn something about its reputation and screening methods. Most women between the ages of 40 and 50 are capable of tracking their mammograms, whether they choose to have those annually, biennially, or less often.

Many CT scans are ordered for patients who are in the hospital – a very different sort of circumstance. Many hospitalized patients don’t feel well, don’t understand what’s happening to them and/or lack the needed assertiveness or language skills to ask about a scan before it’s done.

Summary:

Mammography is a relatively safe and highly-regulated procedure in the U.S.  The recent news on risks from radiation in CT scanning should not confound the discussion of breast cancer screening.

Related Posts:

On Juno and Screening Test Stats

By |December 3rd, 2009

——–
“Well, well” says the convenience store clerk. “Back for another test?”

“I think the first one was defective. The plus sign looks more like a division symbol, so I remain unconvinced,” states Juno the pregnant teenager.

“Third test today, mama-bear,” notes the clerk.

Juno recluses herself and uses a do-it-yourself pregnancy test in the restroom, on film.

“What’s the prognosis … minus or plus?” asks the clerk.

…”There it is. The little pink plus sign is so unholy,” Juno responds.

She’s pregnant, clearly, and she knows she is.

(from Juno the movie*)
——-

Juno\’s pregnancy test
——-
Think of how a statistician might consider Juno’s predicament – when a testing device is useful but sometimes gives an unclear or wrong signal.

Scientists use two terms – sensitivity and specificity – among others, to assess the accuracy of diagnostic tests. In general, these terms work best for tests that provide binary sorts of outcomes – “yes” or “no” type situations. Sensitivity refers to how well a screening tool detects a condition that’s really present (pregnancy, in the teenager’s case). Specificity, by contrast, measures how well a test reports results that are truly negative.**

Juno’s readout is relatively straightforward – a pink plus sign or, not; the possibilities regarding her true condition are few.

Still, even the simplest of diagnostic tests can go wrong. Errors can arise from mistakes in the procedure (a cluttered, dirty store is hardly an ideal lab environment), from flawed reagents (the package might be old, with paper that doesn’t turn vividly pink in case of pregnancy) or from misreading results (perhaps Juno needs glasses).

Why does this matter, now?

The medical and political news are dense with statistics on mammograms; getting a handle on the costs of cancer screening requires more information than most of us have at our disposal.

Of course, breast cancer is not like pregnancy. Among other distinguishing features, it’s not a binary condition; you can’t be a little bit pregnant.  (Both are complicated, I know.)

To get to the bottom of the screening issue, we’ll have to delve deeper, still.

——-
*Thanks Juno, Dwight and everyone else involved in the 2007 film; details listed on IMBD.

———

**I was surprised to find few accessible on-line resources on stats. For those who’d like to understand more on the matter of sensitivity and specificity, I recommend starting with a 2003 article by Tze-Wey Loong in the British Medical Journal. This journal, with a stated mission to “help doctors to make better decisions” provides open, free access to anyone who registers on-line.

I’ll offer an example here, too:

To measure the accuracy of Juno’s kit, a statistician might visit a community of 100 possibly pregnant women who used the same type of device. If 20 of the women are indeed pregnant (as confirmed by another test, like a sonogram), but only 16 of those see the pink plus sign, the sensitivity of the test would be 16/20, or 80 percent. And if, among the 80 women who aren’t due, 76 get negative results, the specificity would be 76/80, or 95 percent.

False negatives: among the 20 pregnant women 4 find negative results; the false negative rate (FN) is 4/20, or 20 percent.

False positives: among the 80 women who aren’t pregnant 4 see misleading traces of pink; the false positive (FP) rate is 4/80, or 5 percent.

Related Posts:

Stats in the News!

By |November 30th, 2009

False positives have hit the headlines.

Check the New York Times, Wall Street Journal, CNN – they’re everywhere. Even the Ladies’ Home Journal skirts the subject.

The discussion on mammography runs something like this: studies show that cancer screening save few lives. Among women younger than 50 years, there’s a high rate of false positive results. Those misleading tests lead to more imaging procedures such as sonograms and MRIs, additional biopsies and, necessarily, higher screening costs.

Women are ignoring the numbers, choosing reassurance over hard facts. Some say members of the pro-mammogram camp are irrational, even addicted.

The best response is to look carefully at the research findings.

Two recent publications sparked the current controversy: one, a single paper in the Journal of the American Medical Association and the other, a cluster of articles in the most recent Annals of Internal Medicine. Using a variety of research tools, the authors in both journals examine the effectiveness of cancer screening. Here, the investigators consider the risks and benefits of mammography from a medical perspective; they don’t focus on monetary aspects of the issue.

The problem of false positives in mammography is most-fully addressed in the AnnalsScreening for Breast Cancer: An Update for the U.S. Preventive Services Task Force. The authors assess, among other newsworthy subjects (such as the value of breast self-examination) the potential risks and benefits of mammography. In the Results section, they delineate five sorts of mammography-associated harms (see “key question 2a”):

1. Radiation exposure – not a big deal, the exposure level’s low;

2. Pain during procedures – women don’t mind this, at least not too much;

3. Anxiety, distress and other psychological responses – the patronizing terms tell all;

4. False-positive and false-negative mammography results, additional imaging, and biopsies – the subject of this and tomorrow’s posts;

5. Over-diagnosis – this interesting and, in my view, exaggerated issue warrants further discussion.

For now, let’s approach the problem of false positives in mammography (as in #4, above).

What is a false positive?

False positives happen in mammography when the images suggest the presence of a malignancy in a woman who doesn’t have cancer in her breast.

How often do these occur?

To their credit, the Annals authors state clearly: “published data on false-positive and false-negative mammography results, additional imaging, and biopsies that reflect current practices in the United States are limited…”

Before we can establish or even estimate the costs of false positives in screening mammography, medical or economic, we need to better define those and, then, establish the frequency with which they occur.

Turns out, the calculation’s not so simple as you might think.

Related Posts:

Another Take on Mammography

By |November 23rd, 2009

In my latest piece, Mammography: a Not-So-Fatalistic View, I outline reasons why the recent task force findings on mammography don’t hold.

Three key issues have escaped the headlines:

1. The expert panel carried out a careful analysis using data that are, necessarily, old;

2. The recommendations don’t apply to digital mammography;

3. Mammograms are not all the same – the quality varies by the methods used and skills of the radiologists who read them.

We need to set the bar higher for mammography. If everyone could have a state-of-the-art mammogram, as I did some years ago, followed by a sonogram to better analyze the tiny abnormalities the radiologist noted (before rushing to biopsy), the stats on cancer screening would be incontrovertible; there would be no debate.

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Getting the Math on Mammograms

By |November 20th, 2009

The latest news’ focus on the breast cancer screening madness is about money.

So let’s do the math:

First, for argument’s sake, let’s say the U.S. Preventive Services Task Force is right – that to save the life of one woman between the ages of 40 and 49, on average, you’d have to screen some 1903 additional women every year or so for a period of 10 years.

This is, admittedly, a huge assumption; the panel analyzed two decades’ worth of data, some unpublished, involving complex models applied to millions of data points (humans) amassed in imperfectly-collected data sets that vary in size, scope and accuracy.

Next, let’s say the cost of a mammogram is $150, around what Medicare pays (yet another assumption, but we need to keep this simple or we’ll never get a sense of what’s really at stake here).

So if 2000 women (I’m rounding up) undergo annual screening for 10 years, the bill would come to $300 thousand per year, for a total cost of $3 million over a decade.  If those same middle-aged women were to get their mammograms biannually (every other year), the cost would be roughly $1.5 million per life saved.

This, the so-called cost of screening mammography for women between the ages of 40 and 49 (let’s call it “X”), is all over the news in various calculations, some that get closer to the right answer than others.

But what’s the cost of caring for one 45 year old woman with metastatic breast cancer?

Let’s call that amount “Y.”

Even the heartless among us would admit that we need to subtract, X-Y, to determine the financial cost of breast cancer screening to save one middle-aged woman’s life.

An insurance executive might say it’s in the range of $400 thousand, or a million dollars, or maybe even two million, if the woman lives long enough to go in and out of the hospital over the course of five years, undergo multiple surgical procedures, have semi-permanent intravenous catheters inserted and removed, suffer infections from those requiring at-home multi-week courses of intravenous antibiotics, all of this besides, of course, receiving chemotherapy, radiation, hormone treatments, incalculably expensive antibody infusions and newer, targeted therapies, followed by hospice (hopefully) or ICU care in the end.

Quick answer: maybe it’s cost-effective, or nearly so, to do screening mammograms on asymptomatic women in their forties.

But consider -  if the expert panel’s numbers are off just a bit, by as little as one or two more lives saved per 1904 women screened, the insurers could make a profit!

By my calculation, if one additional woman at a cost of, say, $1 million, is saved among the screening group, the provider might break even.  And if three women in the group are saved by the procedure, the decision gets easier…

Now, imagine the technology has advanced, ever so slightly, that another four or five women are saved among the screening lot.

How could anyone, even with a profit motive, elect not to screen those 2000 women?

The truest answer, of course, is that the value of any one person’s life is inconceivably huge.  And that doesn’t even enter into the equation.

Related Posts:

To Screen is Human

By |November 17th, 2009

Smack in the midst of October-is-breast-cancer-awareness-month, the Journal of the American Medical Association published a provocative article with a low-key title:  “Rethinking Screening for Breast Cancer and Prostate Cancer.”  The authors examined trends in screening, diagnosis and deaths from cancer over two decades, applied theoretical models to the data and found a seemingly disappointing result.

It turns out that standard cancer screening is imperfect.

The subject matters, especially to me.  I’m a medical oncologist and a breast cancer survivor, spared seven years ago from a small, infiltrating ductal carcinoma by one radiologist, an expert physician who noted an abnormality on my first screening mammogram.

The New York Times featured the new findings in a front-page article that elicited over 200 readers’ comments.  Quite a few cheered the frank, non-party line that mammography‘s not all it’s cracked up to be.  Same goes for measuring the prostate specific antigen in men’s blood, a test that sometimes marks for prostate cancer.

Some readers connected the dots between cancer screening, the pharmaceutical industry and physicians’ income.  Because doctors make money by interpreting scans, doing biopsies and giving chemotherapy, perhaps they can’t be trusted to make unbiased recommendations.  Like an aggressive tumor, the story spread everywhere – cable news, NPR, a host of blogs.

Fear, hassle, insurance forms (if you’re lucky), blood tests, anxiety, CAT scans, possibly a cancer diagnosis with attendant surgery, radiation, chemotherapy, nausea and who knows what else ensues.  Yuck.  The toll is huge, even apart from the finances.

The Food and Drug Administration estimates that radiologists perform some 37 million mammograms each year in the United States.  Women undergo 70 percent of those scans for routine screening purposes.  (Doctors order the other 30 percent to evaluate lumps or other signs of cancer that’s already evident.)  My math:  that’s 26 million screening mammograms at, roughly, $100 per scan, for a total cost of $2.6 billion annually.

Compounding the confusion, a few days later the Times ran a related piece highlighting reports that some tumors shrink or even disappear without treatment.  That’s wonderful news, if it’s true.  Perhaps you can skip the mammogram, not find the cancer, and it’ll just go away.

This represents a form of wishful thinking.  Reality check in three points:

1. Prostate cancer is not the same as breast cancer.  You can’t simply lump these together in a study and draw conclusions about testing or treatment for either condition.

2.  Breast cancer is a common and very real cause of death in North America, where each year there are nearly 200,000 new cases and more than 40,000 associated deaths.

3. Mammograms save lives by uncovering tumors when they’re still small enough for surgical removal.

In 2009, there is no known cure for metastatic breast cancer.  A woman’s chances of surviving for five years after she’s found to have a small, localized tumor lie in the 98 percent range; if she’s noted with metastatic disease, those odds hover around 25 percent.

So what’s a woman to do?

Sure, it’s discomfiting to know that screening doesn’t always work.  And for some, it’s disheartening that doctors, insurance companies and x-ray machine makers generate profits by detecting, evaluating and treating cancer.  In case you haven’t been following the health care reform debate, health care’s an imperfect business.

Many will continue to go for annual mammograms, especially in October, and their doctors will, emphatically, recommend that they get those.  And many men will request of their internists, or urologists, or whoever’s taking care of them, that they get a blood test for prostate cancer, “just to be sure.”  Likely, a few more skeptics will opt out of the screening process.

Screening for breast and prostate cancer could be better.  The same applies to pretty much everything in health care, as in any human enterprise.  But it’s the best that we’ve got, for the time being.

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