The Manhattan Project of Breast Cancer

An enormous, federally funded project, the Cancer Genome Atlas Network, has yielded from 825 patients the first comprehensive genetic analysis of breast cancers. Until recently, a clinician's approach to thinking about breast cancer was basically to divide it into three categories: hormone receptor–positive, human epidermal growth factor receptor 2 (HER2)–positive, or so-called triple-negative (estrogen receptor [ER]–, progesterone receptor [PR]–, and HER2-negative) breast cancer. This classification largely reflected the treatment approaches that were available for each: endocrine therapy for hormone-sensitive breast cancer, anti-HER2 therapy for HER2-positive disease, and chemotherapy for everything else.

In the last few years, molecular t…