This week I’ve been reading about new developments in breast cancer (BC) pathology.
At one level, progress is remarkable. In the 20 years since I began my oncology fellowship, BC science has advanced to the point that doctors can distinguish among cancer subtypes and, in principle, stratify cases according to patterns of genes expressed within tumors. This sort of information – cancer cell profiling – might inform prognosis and influence treatment decisions that BC patients and their doctors, usually oncologists, make every day.
What disappoints is the slow pace by which this knowledge infiltrates the clinic. In practice, women and their physicians rarely have much more information on BC pathology than what was available two decades ago – the tumor size in its largest dimension (crudely measured in centimeters), whether it’s spread to the lymph nodes (and if so, how many nodes), the type of cancer (based on the cells’ appearance under a light microscope: infiltrating ductal, lobular carcinoma and other BC forms) and whether the cells express a few key molecules including estrogen receptors (ER).
In the past five years, more laboratories are offering data on Her2 in BC samples. This complex molecule, an epidermal growth factor receptor, normally transmits signals from a cell’s surface to the interior. Her2 expression dictates the BC subtype in some newer classifications of the disease and usually determines the cells’ responsiveness to Herceptin, a monoclonal antibody treatment. Still, there’s been some controversy, in part due to variation among lab facilities in the reproducibility of Her2 testing results.
The problem is this: if pathologists don’t provide accurate, valid results on Her2 expression in BC cells – which can be measured by various methods – it’s hard for women and their physicians to make sound decisions based on the molecule’s expression. And Her2 is just one of dozens of molecules that can be measured in BC. The reason it’s tested, for the most part, is to foster decisions on Herceptin treatment and also, perhaps to a lesser extent, to provide prognostic information.
What puzzles me is why so few use better, modern pathology and other decision tools. Technologies like Mammaprint, Adjuvant! and OncotypeDx have been available for years but aren’t used routinely in most clinical settings. So I thought I’d do some more research and, in future posts, will consider each of these and other, relevant technologies.
For today I’ll focus on OncotypeDx. This test, manufactured by the Redwood City, California-based Genomics Health, assesses BC recurrence risk in cases that are ER+, node negative (see below). As cancer gene testing panels go, OncotypeDx is a baby, based on expression of just 21 genes by a two-decade old method called quantitative RT-PCR. The test intrigues me; I’ve posted on it once before.
No doubt, my interest in OncotypeDx is intensified by my personal history of BC. My case was exactly the sort of ER+, node-negative tumor for which OncotypeDx is intended; often I’ve wondered what would have been my tumor’s recurrence score (RS) and if knowing that would have affected my decision to undergo treatment with adjuvant chemotherapy.
Some background terms –
ER+ means that the cells express hormone receptors, for estrogen, at the surface;
Node negative means that the breast cancer has not spread to the lymph nodes, or glands, of the armpit. (Axilla is the medical term for armpit. Axillary lymph nodes are normal immune organs that drain fluid including potentially foreign particles from the breast, chests and nearby arm. The nodes can swell if there’s an infection to which the body reacts, if malignant cells infiltrate the gland and sometimes due to autoimmune diseases like lupus.)
So an ER+, node negative breast tumor is one in which the cancer cells are sufficiently differentiated, or mature, to produce and bear hormone receptors at their surfaces and in which the tumor cells haven’t yet migrated to the armpit (or at least haven’t done so at a level that can be detected by a pathologist).
Real-Time, Reverse Transcriptase (RT) – Polymerase Chain Reaction (PCR) is a standard method for amplifying tiny amounts of nucleic acids such that they can be measured and sequenced. Standard PCR usually amplifies DNA whereas in RT-PCR, RNA transcripts are converted to DNA before amplification in a machine. This method can assess the amount of RNA, or message for a particular gene, that’s expressed in a pathology sample.
Adjuvant therapy refers to additional, or extra, treatment that’s given after initial cancer surgery to reduce the chances of the tumor’s recurrence.
Back to OncotypeDx –
This pathology tool predicts the likelihood that ER+, node-negative BC tumors will come back within 10 years of a woman’s primary treatment (mastectomy, or lumpectomy with radiation) usually followed by tamoxifen. The assay measures each of 21 genes in a panel and, using those results, calculates a “recurrence score” (RS) between 1 and 100. The higher the RS, the more likely the cancer will re-emerge after treatment.
According to the Genomics Health website, the test measures RNA in BC tumor specimens for the following transcripts:
|Groups of genes measured in OncotypeDx assay, according to the manufacturer|
|cell proliferation||tumor invasiveness||growth factor receptors||hormone responsiveness||other genes of interest||reference** genes|
PR (progesterone receptor)
*In my opinion, survivin and bcl-2 might be better classified distinctly; the products of these genes inhibit apoptosis (programmed cell death).
**These “housekeeping” genes are not of known significance in BC pathology. Rather, they serve as controls in the assay for the quality of the RNA sample, and for comparison to other measured genes.
The OncotypeDx results are reported by risk group, as follows:
Low risk (RS <18, the 10-year recurrence rate was 7% in NSABP study – see below)
Intermediate (RS 18 – 30, the 10-year recurrence rate was 14%, in same);
Higher risk (RS >31, the 10-year recurrence rate was 30%, in same).
The tool has been tested in multiple clinical trials for its capacity to predict BC recurrence after surgery and tamoxifen in women with ER+, node-negative tumors. The study most-cited, and from which the above statistics are drawn, was published in the New England Journal of Medicine in 2004, based on a retrospective analysis of 668 cases by Genomics Health in collaboration with investigators of the National Surgical Adjuvant Breast and Bowel Project (NSABP, a large, NIH-sponsored, multicenter cancer research effort).
OncotypeDx has been on the market since 2004. The cost of one assay runs near $3800, and most U.S. insurance plans including Medicare will cover it. Tumor samples, set in fixative, are sent to a single lab – a Genomic facility – that’s regulated according to the Clinical Laboratory Improvement Amendments of 1988 (CLIA). The whole process takes 10-14 days. Still, the FDA has not approved the test for use as a decision-making tool.
Meanwhile, an NCI-sponsored trial called TAILORx will recruit and evaluate 10,000 women with ER+, node negative disease. Those investigators will determine, prospectively, if decisions based on OncotypeDx results can safely spare women with low RS the side effects and toxicity of chemotherapy without compromising their survival.
Why Oncotype and other new BC pathology tools matter –
In the U.S., the number of women who learn they have an ER+, node-negative BC approximates 100,000 per year. The question of adjuvant therapy – whether a woman should take tamoxifen or another hormonal agent and/or chemotherapy after surgery to reduce the risk of recurrent disease – is crucial.
If patients and their doctors could access more detailed molecular information about each case, they’d have a better sense of whether adjuvant treatment is likely to help in their particular situation. This approach would, potentially, spare many individuals with early-stage BC the costs, toxicity and hassle of unneeded chemotherapy. At the same time, it would help patients with small but riskier tumors by informing them that they have a high RS and thereby would more likely benefit from added therapy. Fewer women would receive chemotherapy, driving down costs, and the risks of additional treatment would be assumed only by those with a high likelihood of recurrence.
Some numbers here might help:
Overall, for women with ER+, node-negative tumors the chances of cancer recurring five years after primary treatment (mastectomy, or lumpectomy and radiation) followed by tamoxifen are around 15%. Over time that risk rises – BC can strike back after 10, 15 years or even later; the recurrence rate is said to approach 30% over time. In general, a basic chemotherapy regimen – something like CMF – cyclophosphamide (Cytoxan), methotrexate and 5-fluorouracil (5FU) reduces the probability of recurrence by about a third.
So if 100 women with node-negative tumors have to decide whether to take chemotherapy after surgery +/- radiation, or not, without a tool like OncotypeDx or another modern pathology test, they’re making those decisions based on very crude approximations of their odds. Because they don’t know whose tumors will recur, most if not all of their oncologists will recommend chemotherapy. And most women do choose to undergo the extra treatment because they’re afraid that, otherwise, there’s a greater chance the cancer will come back.
This is exactly the situation I faced in November, 2002, when I had an ER+, node negative, 1.5 cm tumor. Then, I reasoned that BC tends to be more aggressive in younger women. With hopefully more decades ahead in my life – more time, in effect, for the disease to recur – an 85% disease-free rate at 5 years wasn’t good enough. So I went for the chemo and upped my chances to the 90% range. Not a big difference in the stats, but I wanted to position myself on the upper branch of that Kaplan-Meier curve. Now, had I known my recurrence score based on the pattern of gene expression in the tumor cells, that information would have been useful. But it wasn’t an option then and, unfortunately, it’s still rarely available to most women who are undergoing treatment for BC in 2010.
The slow pace of progress, science in hand, is kind-of shocking.
So what’s new with OncotypeDx?
Two months ago, I reviewed a small study published in the ACS Cancer journal on the experiences of most of 100 women with newly-diagnosed breast cancer whose oncologists used the OncotypeDx assay to evaluate their cases. In that, two-thirds of the women reported they “understood a large amount or all” of what the doctors told them about the results and nearly all said they would undergo the test if they had to decide again.
In its April 1 issue the Journal of Clinical Oncology (JCO) published two relevant reports and an editorial. These papers support that OncotypeDx offers useful information to women with early-stage breast cancer and that it can assist patients and doctors in care decisions, in some cases providing support for them to choose a chemotherapy-free treatment regimen.
One study, a “Prospective Multicenter Study of the Impact of the 21-Gene Recurrence Score Assay on Medical Oncologist and Patient Adjuvant Breast Cancer Treatment Selection” by Dr. Shelly Lo and colleagues, followed the analysis and prescribing patterns of 17 medical oncologists at 3 diverse academic medical centers and one community hospital. Genomic Health, provided free OncotypeDx kits and testing at their central lab for all 93 patients with ER+, node-negative BC who enrolled in the trial.
The mean age of the women was 55 years (range 35 – 77). The oncologists were asked to state their treatment preferences (hormonal treatment with or without chemo) before and after receiving the OncotypeDx results for their patients. What happened was this:
Before seeing the OncotypeDx results, the oncologists recommended chemo and hormonal therapy (CHT) to 42 of the 89 women for whom the study was completed. In 20 of those 42 cases (22% of the total, and nearly half of those women who were to receive chemo) the doctors changed their recommendation from CHT to HT (hormones only) upon reviewing the OncotypeDx report. In 8 cases, the oncologists switched their recommendation to include chemotherapy. In total, the OncotypeDx results influenced the oncologists’ preferences in 31% of the cases – nearly a third.
As for the patients – 74 of the 89 (83%) said the OncotypeDx results influenced their treatment decision. The assay report persuaded 9 patients in the group to opt for a less aggressive (chemo-free) approach. The majority (78 women, 95% of those responding) said they were glad they used the OncotypeDx assay. According to the paper, many patients felt reassured by the assay findings and benefited from a diminished perceived risk of recurrence (less worry, in effect).
The upshot is that the OncotypeDx assay – which costs around $3800 per evaluation – led to significantly fewer women with early-stage breast tumors getting chemotherapy in this trial of 89 patients. The doctors were more confident in their decisions to not give chemotherapy in cases with low RS and, overwhelmingly, the women felt glad about the decision-making process.
In the second JCO study in the April 1 issue, the number of patients evaluated was much greater – over a thousand. But this was a more complicated analysis in which the investigators applied OncotypeDx to old tumor samples and then, upon reviewing those cases in some well-documented randomized trials, examined how the cases fared in relation to the RS. What they found was that OncotypeDx score predicted the likelihood of loco-regional recurrence (LRR) in women who had node-negative, ER+ disease.
Bottom line –
The OncotypeDx tool has been on the market for 6 years. It has, in multiple and well-done studies, identified patterns of BC gene expression that accurately predict the likelihood of recurrence in women with early-stage, ER+, node-negative tumors. This should, in principle, reduce administration of chemotherapy – along with its attendant risks, costs and side effects – to women whose tumors are unlikely to relapse. Recent trials show that doctors find the results useful and that patients find it helpful in their decisions.
I can’t know for sure why the tool’s not used more often. But I have some concerns:
1. It takes time for doctors – even knowledgeable oncologists – to learn about this device, to know how it differs from other BC pathology tests like Mammaprint and decision tools (like Adjuvant!) and then it takes even more time for those physicians to discuss the results with their patients.
From the perspective of a physician sitting behind her desk or at a table with a newly-diagnosed BC patient, saying “this is what I think, you need treatment X” may be a lot easier than “well, let’s go over these OncotypeDx results…”
2. If the OncotypeDx report does indeed identify large subgroups of early-stage breast cancer patients who don’t need chemotherapy, the use of this test would reduce the number of patients who get chemotherapy. Oncologists, infusion centers and others generate income by prescribing chemotherapy. So there’s a potential conflict of interest.
3. Perhaps some physicians fear lawsuits for not giving chemotherapy to women who, without the OncotypeDx results, would receive it.
4. Some doctors might not recommend OncotypeDx because they don’t really understand the test, its merits and limitations.
5. Maybe OncotypeDx isn’t the best of the new BC adjuvant therapy decision tools. For this reason, among others, I will consider some of the other methods available in future posts.