By Karuna Jaggar, Executive Director

When we speak about advances in medicine, most people think of new treatments that work better than existing treatments, or maybe work as well as existing treatments but come with fewer side effects. Rarely is a reduction in the numbers of people who receive treatment seen as an advance.

But that was exactly the buzz this weekend at the annual meeting of the American Society of Clinical Oncology. A new study will transform treatments for the most common type of breast cancer: instead of adding a new treatment, the TAILORx study results released this weekend dramatically expanded the number of women with hormone positive breast cancer who can safely skip chemotherapy.

TAILORx used a common genomic test, Oncotype DX, to identify which women with early stage, hormone positive breast cancer which has not spread to the lymph nodes who do not need to receive chemotherapy. Chemotherapy has long been a mainstay of breast cancer treatment. Oncotype DX has been marketed since 2004 to predict the likelihood of cancer recurrence for this group of patients after surgery. However, until now, the test was most useful only for those patients with the lowest and the highest scores (under 10 and over 25, respectively).

Around one in six patients receive a low Oncotype score (10 or lower) which indicates a low risk of recurrence and no likely benefit from chemotherapy. Another one out of six patients receive a high Oncotype score (above 25) indicating a likely benefit of chemotherapy. The remaining two thirds of patients receive an intermediate score (between 11-25), which until now has been a relative gray zone where the likelihood benefit of chemotherapy was not well understood. With cancer, too often the default is generally more is better and as a result most women in these situations have been treated with chemotherapy.

The TAILORx study divided close to seven thousand women with hormone receptor positive, HER2 negative, node negative early stage breast cancer with an intermediate OncotypeDX score (between 11 and 25) into two groups after surgery: one group received the standard chemotherapy plus hormone therapy while the other group received only hormone therapy. At nine years, overall survival and recurrence were essentially the same in the two treatment groups, although some benefit of chemotherapy was found in women under age 50 with a recurrence score of 16 or above.

The results of this large, well designed study that followed women for nearly a decade is considered practice changing. The researchers concluded that women over age 50 with an Oncotype score of 25 or lower do not need to be treated with chemotherapy for hormone positive, lymph node negative breast cancer. Patients age 50 or younger with an Oncotype score of 16 or above may get some benefit from chemotherapy, the researchers said. Dr. Joseph A. Sparano, of Montefiore Medical Center, who presented the study results said that practically, this means: “Application of this test in clinical practice in this population could be estimated to spare chemotherapy in 69% and to select chemotherapy in 31%, on average.”

The ability to reduce overtreatment, is in fact a huge step forward in breast cancer treatment. While it does not overshadow the need for more effective treatments so fewer women die from the disease, the ability to spare tens of thousands of women each year from the harmful effects of chemotherapy that is not benefiting them is undoubtedly a major medical advance.