Predicting Breast Cancer's Return

Tuesday's announcement by the U.S. Food and Drug Administration that it had approved the MammaPrint test represents a step forward in our efforts to more precisely define which women with breast cancer require adjuvant (preventive) chemotherapy following primary treatment for the disease.

Adjuvant chemotherapy for breast cancer has been one of the great success stories in cancer treatment over the past 30 years. Through the efforts of many researchers, women and their families, we have learned how to prevent recurrence of breast cancer and increase survival for many women with breast cancer. As a result, we have seen steady declines in the death rates for women with breast cancer.

We also know that we provide adjuvant chemotherapy to many women with primary breast cancer who would have otherwise done well without additional treatment. But the types of tests and information about a particular woman's breast cancer that we have available today are simply too imprecise to allow us to accurately and confidently separate women at high risk of developing recurrent of breast cancer from those who are at low risk of recurrence.

If we could do this, we could potentially avoid chemotherapy in the low-risk women, and thus free them from the need to take adjuvant chemotherapy along with its associated costs, inconvenience and side effects.

Predictive Tests Improving

Over the past several years, there have been several tests developed that have moved us closer to predicting which women with breast cancer have the best chances of survival, and those who would likely benefit from chemotherapy.

A recent study in the August 10, 2006, issue of New England Journal of Medicine reviewed the performance of several of these various breast cancer prognostic tests (including MammaPrint). The researchers reported that although the fundamental approaches of the tests were different, several of them had similar outcomes when predicting which women had the greatest likelihood of developing recurrent breast cancer.

However, as noted in an editorial that accompanied the article, the real question is whether any of these tests add value and useful knowledge to the treatment of women with early stage breast cancer.

The editorialist agreed that there was excellent agreement among the tests in predicting the risk of breast cancer recurrence. These tests also added more accurate information about prognosis than was available from more standard approaches we have available to assess the aggressiveness of a particular woman's breast cancer.

But, in practical terms, it was not clear that these tests added sufficiently more information about a particular cancer so that a doctor could reliably tell a woman that she did or did not require adjuvant chemotherapy.

Treatment Change Unlikely

The bottom line is that these tests, such as MammaPrint, are an important first step in helping us understand the biology and behavior of a woman's breast cancer.

It is unlikely that many doctors are going to change their treatment recommendations based on these tests. The times these tests affect actual treatment decisions made by women with breast cancer and their doctors will more often be the exception rather than the rule.

Over time, we can expect that these predictive tests will become more accurate so that we can rely on them to help us determine which women need adjuvant treatment for breast cancer and which women do not.

Until that time, and until clinical trials are completed, which will provide us practical guidance on the utility of these tests, we are likely going to continue our current approaches to making recommendations for adjuvant treatment of primary stage breast cancer.

Dr. Len Lichtenfeld is deputy chief medical officer for the American Cancer Society. You can view the full blog by clicking here.

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