As part of an ongoing series of answers to common questions received by the Basser Center for BRCA, Executive Director Susan Domchek, MD, discusses the differences between BRCA1 and BRCA2 mutations and explains how the varying risk factors could impact individuals and their families.

Dr. Domchek: One of the questions we frequently get is whether there's a difference between BRCA1 and BRCA2 mutations. It's important to know that although these these genes sound the same, they are completely different genes and they make completely different proteins. It just turns out that in the cell, when there's DNA damage, the two of them cooperate together to help repair the damage. So they're related to each other, but they're definitely distinct. And it also means that the types of cancers that are associated with these genes are different. So for BRCA1, the risk of ovarian cancer, for instance, is higher than for BRCA2 with a lifetime risk of 40 to 45 percent for BRCA1 compared to maybe 10 to 20% for BRCA2. In addition, the ovarian cancer risk seems to occur earlier for BRCA1 than for BRCA2 on average.

The types of breast cancers are different between BRCA1 andBRCA2. BRCA1 associated breast cancers are generally what we call triple negative, estrogen receptor negative, progesterone receptor negative, and HER2 new negative. Whereas BRCA2 associated breast cancers are generally estrogen receptor positive. Not always, but more often than not. In addition, other risks that we associate with these genes, for instance, male breast cancer, pancreatic cancer, and prostate cancer are much more strongly associated with mutations. And BRCA2, for all these reasons, when we talk to individuals about their screening and prevention options, we do take into account these differences between BRCA1 and BRCA2.