The Reliability of Oncotype DX

Estrogen-receptor-positive (ER+) breast cancers are fueled by estrogen and treated with therapies that block the hormone. Some women also receive chemotherapy to reduce the likelihood of cancer recurrence. The Oncotype DX assay is a diagnostic test that can help women with early-stage, ER+ breast cancer and their physicians determine the likelihood of cancer relapse and whether or not chemotherapy treatment is warranted.

Function

• The Oncotype DX assay uses a tumor tissue sample to analyze genetic activity and predict how a cancer may grow and respond to treatment. Analysis provides a recurrence score, a number between 0 and 100 that corresponds to the likelihood of cancer recurrence. Low scores indicate low risk and suggest that chemotherapy may not be necessary.

Expert Insight

• According to the Eastern Cooperative Oncology Group, many tests and several clinical trials support the validity and reliability of Oncotype DX. It claims the test is more accurate than traditional methods for predicting breast cancer relapse in some women. The American Society for Clinical Oncology and the National Comprehensive Cancer Network now include the test in their treatment guidelines for early-stage breast cancer.

Limitations

• As of 2010, Oncotype DX testing is recommended only for women with ER+ cancers that have not spread beyond the breast to the lymph nodes, and possibly post-menopausal women with ER+, node-positive breast cancer. The behavior of cancers with intermediate-risk recurrence scores remains unclear.