Oncotype DX Testing and the TAILORx Trial



Patrick I. Borgen, MD: We get a lot of questions about Oncotype DX. What is it? How does it work? What does it tell us? It's important in answering that question to understand that breast cancer is not a single disease. Breast cancer is a large, complicated family of diseases, and within that family, you have breast cancers that respond almost exclusively to blocking estrogen. In those breast cancers, blocking estrogen is our best weapon. And you have breast cancers that respond to cytotoxic chemotherapy or immunotherapy, including drugs like trastuzumab. Within the subset of estrogen receptor-positive, HER2-negative breast cancers, both node negative and node positive, we use Oncotype DX to determine the prognosis and predict response to therapy. This tells us whether a patient will benefit from chemotherapy, or will get all of her benefit from blocking estrogen.

This is historically important. In the 1990s through the early 2000s, every woman with a breast cancer greater than 1 cm in maximum diameter got chemotherapy—big tumors, small tumors, node negative, node positive. That was based on randomized trials that showed a benefit to chemotherapy, but it was a small benefit. Back in those days, we were treating, for example, 100 women to help 6 or 8 of them. We didn't know who the 8 were, so we treated everyone. Oncotype DX lets us personalize our approach. It lets us be far more precise in administering treatment to women with breast cancer.

TAILORx is a landmark trial. In fact, it is the largest randomized drug trial ever in the history of human breast cancer. TAILORx had 3 important groups. Based on an Oncotype DX score, there was a designated low-risk group. These were patients with a score of less than or equal to 11. Early on, we saw in the first TAILORx report that the low-risk group, with no chemotherapy, just blocking estrogen, had a 97% 5-year disease-free survival. That is one of the most incredibly favorable results we've ever seen from a trial. At the high end, the third group in the trial, comprised of patients with a high recurrence score, received cytotoxic chemotherapy in addition to estrogen blockade.

The interesting group included those patients with an intermediate score. Those patients were randomized to receive estrogen blocking alone or estrogen blockade plus chemotherapy. What we saw was that for patients across the board with a score less than or equal to 25, all of the benefit was from blocking estrogen. Those patients did not benefit from chemotherapy. There is a subtlety. For patients below the age of 50 who had scores in the 17 to 24 range, there was a small benefit from chemotherapy, ranging from 1% to 6%, depending on the Oncotype DX score. What does this mean? We are tailoring the treatment. We are selecting the treatment that matches the disease in the patient in front of us, but we are also decreasing the use of cytotoxic chemotherapy, and that is incredibly important.

In terms of patient impact, patients with estrogen receptor-positive, HER2-negative breast cancer make up about 60% of all breast cancers in the Western world. Based on TAILORx, we know that about 60% of patients had that low score. You're eliminating cytotoxic chemotherapy in a very large subset of patients who simply would be subjected to the risks and potentially life-threatening adverse events with no benefit. This impacts lives. This is real.

Transcript Edited for Clarity

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