Don’t Blur the Message on Cancer Screening
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,