Hereditary breast-ovarian cancer (HBOC) syndrome is an autosomal dominant cancer predisposition syndrome caused by germline BRCA1/2 mutations.
Mutations in these two highly penetrant genes increase the chance for cancer of the breast, ovaries and fallopian tubes, pancreas and prostate. Studies suggest female BRCA1 mutation carriers have between a 57-87% risk to develop breast cancer and between a 39-40% risk to develop ovarian cancer by age 70. Similarly male BRCA1 mutation carriers have a cumulative breast cancer risk of 1.2% by age 70.
Similar studies suggest female BRCA2 mutation carriers have between a 45-84% risk to develop breast cancer and between an 11-18% risk to develop ovarian cancer (including primary peritoneal and fallopian tube) by age 70. Male BRCA2 mutation carriers have up a 15% prostate cancer risk and a cumulative breast cancer risk of 6.8% by ages 65 and 70 respectively.
Furthermore, BRCA1/2 mutation carriers are at an increased risk for melanoma and cancer of the pancreas, gall bladder, bile duct and the stomach. Cancer risks are further modified by family history, reproductive choices, lifestyle and environmental factors and other genetic factors.