Molecular Testing in Breast Cancer: An Oncologist’s Perspective
Medical oncologists try to tailor treatment to each individual woman’s cancer’s biologic and clinical features. These features determine the risk of relapse and drug sensitivity for early breast cancer and the prognosis and treatment options for late breast cancer. Gene expression tests, including OncotypeDx, MammaPrint, Prosigna, and BCI, attempt to measure factors such as ER activation and proliferation to provide estimates of prognosis and chemotherapy sensitivity in early ER-positive breast cancer. They each provide similar information, and clinical factors such as age, tumor size, and grade retain independent prognostic value. In metastatic breast cancer, circulating tumor cells (CTCs) are prognostic and can be used to detect mutation, but cannot be used currently to guide choice of chemotherapy. Ongoing trials are assessing the use of therapy based on mutations in CTCs or in tumor themselves.
