Does Oncotype DX testing reduce the use of chemotherapy in patients with estrogen receptor positive breast cancer?

In this study, researchers evaluated whether a genetic test called Oncotype DX, reduced the use of chemotherapy treatment for patients with node-positive and estrogen-receptor positive breast cancer.

Some breast cancers grow in response to estrogen, the main female sex hormone, via their receptor (a protein found on the surface of the cancer cells). These are called estrogen-receptor positive (ER+) breast cancers. When cancer has spread from the breast to the nearby lymph nodes, it is called node-positive (N+) breast cancer.

Oncotype DX is a genetic test used to evaluate the risk of cancer recurrence (return of the cancer), that works by examining a sample of the cancer. The test measures specific genes (instruction segments in the genetic material), to see how active they are (also known as how they are expressed). The result of the test is reported as a number between 0 and 100, known as the recurrence score. A lower score means the cancer has a lower risk of returning. The recurrence score can also indicate whether additional chemotherapy is needed to prevent recurrence. In patients with a low recurrence score, chemotherapy is unlikely to provide additional benefit.

To assess whether Oncotype DX testing reduces the need for chemotherapy treatment, researchers compared 951 patients with N+ER+ breast cancer. 282 patients received Oncotype DX test results before deciding on treatment, and 669 patients did not undergo Oncotype DX testing before treatment. In the group tested with Oncotype DX, 18 patients received high recurrence scores, and received chemotherapy. 108 patients received an intermittent recurrence score, and only 37% of these patients required chemotherapy. The other 156 patients received a low recurrence score, and only 7.1% of these required chemotherapy. By comparison, 70.1% of the patients in the group not tested with Oncotype DX received chemotherapy. 

The authors concluded that Oncotype DX testing significantly reduced the use of chemotherapy among patients with N+ER+ breast cancer.

The two groups in this study were significantly different. Patients who did not receive Oncotype DX testing had more advanced cancers, which are more likely to require chemotherapy. Therefore, it is difficult to assess whether patients who received Oncotype DX testing were less likely to receive chemotherapy as a result of their less advanced cancers, or due to their test results. However, the researchers attempted to correct this by performing a matching statistical analysis, which takes these factors into account. In addition, this trial was supported by the manufacturers of the Oncotype DX test.

Consult with your physician about Oncotype DX testing to assess your recurrence risk and need for chemotherapy.