Comparing genetic tests for predicting risk of cancer recurrence in breast cancer patients

This study assessed the efficacy of using a new test called the 95-gene classifier (95-GC) to foretell the likelihood of cancer recurrence (return of the cancer) in patients with estrogen-receptor positive and node-negative (cancer that has not yet spread into the lymph nodes) breast cancer. 

Estrogen-receptor positive (ER+) breast cancer is a type of breast cancer caused by estrogen, the main female sex hormone. Estrogen helps breast cancer growth by attaching to certain proteins on the surface of breast cells called estrogen receptors (ER). ER+ breast cancer patients can usually be treated with hormone therapy, which stops estrogen from getting to the cancer, thus stopping the growth of the cancer. However, some patients need additional treatments such as chemotherapy to avoid cancer recurrence. To evaluate the risk of recurrence and which patients can benefit the most from additional chemotherapy, there have been developed genetic tests such as the 21-gene classifier (21-GC) and the 95-GC. 

21-GC, also known as Oncotype DX is a genetic test that evaluates the risk of breast cancer recurrence and classifies breast cancer patients into low, intermediate and high-risk by examining a set of 21 genes. This method is already approved and is the most commonly used as a recurrence predictor in women with ER+ and node-negative breast cancer. The 95-GC is a newly developed test that examines a set of 95 genes. It classifies patients into high and low-risk of recurrence and has showed that low-risk patients have an excellent prognosis and can be safely spared from chemotherapy. The two sets of genes evaluated in both tests are completely different. This study was aimed to compare the efficacy of 95-GC and 21-GC, as well as the combination of the two genetic tests in predicting breast cancer recurrence risk.

A total of 459 ER+, node-negative breast cancer patients who have been treated with hormone therapy were involved in this study. The 95-GC classified 174 patients as a high-risk group and 285 as a low-risk group. The likelihood of disease recurrence in high-risk patients was higher than in low-risk patients. The 21-GC classified 286 patients as low-risk, 81 as intermediate-risk and 92 patients as high-risk. Also, low-risk patients had a better recurrence outcome than the other two risk groups. Furthermore, patients classified by the 21-GC as intermediate-risk were reclassified as low-risk (38 patients) and high-risk (43 patients) with the 95-GC. The 38 low-risk patients showed a better outcome compared to high-risk patients. When the two methods were combined, 324 patients were classified as low-risk and 135 as high-risk group. The low-risk patients as classified by the two tests combined showed a significantly better prognosis compared to the high-risk group.

In summary, this study showed that the 95-GC can give the same result as the 21-GC in predicting breast cancer recurrence. The purpose of these tests is to select patients who have an excellent prognosis with hormone therapy only and may be spared from chemotherapy. When the two methods are combined, they are more effective in selecting patients with a good prognosis compared to either test alone.

Ask your doctor about genetic testing for predicting breast cancer recurrence risk.