As part of an ongoing series of answers to common questions received by the Basser Center for BRCA, Executive Director Susan Domchek, MD, discusses different types of hereditary breast cancer.
BRCA1 and BRCA2 mutations both increase the risk of developing breast cancer, but the breast cancers that develop in the setting of the different mutations differs. BRCA1 mutation associated breast cancers are generally what we call triple-negative breast cancers. What we mean by that is that they're estrogen receptor negative, progesterone receptor negative, and HER2/neu-negative. What that means on a practical level is that if we're treating breast cancer in a BRCA1/2 mutation carrier, most the time things like hormonal therapies and a drug called Herceptin won't be used, because those are not the types of breast cancers that BRCA1 carriers usually get. Having said that, every time someone's diagnosed with breast cancer, we test for those three markers and we treat the cancer based on what we find at the time of pathology.
BRCA2 mutation carriers, most of the time, have estrogen receptor positive tumors and again that means that we can use hormonal therapies to help treat those cancers. BRCA2 mutation carriers certainly can get triple negative breast cancers as well, it's just that most of the time, they're estrogen receptor-positive.