Breast cancer (BC) is the most common cancer in women, accounting for 25% of all new cases of cancer. Most BC cases are sporadic, while 5-10% are estimated to be due to an inherited predisposition. Autosomal dominant alterations in two genes, BRCA1 and BRCA2, are likely to account for most familial cases of early-onset BC and/or ovarian cancer (OC), and for 3-4% of all BC. Prevalence of germline BRCA mutations has been estimated to be about 1:1,600 women in the general population. The lifetime risk of developing hereditary BC (HBC) and/or OC can reach 80%. For a given mutation in the susceptibility gene, disease severity and age at onset show great variability within and between BC families, suggesting the involvement of other genetic as well as non-genetic factors. HBC is not associated with specific phenotypic features and diagnosis relies upon the following characteristics: increasing numbers of affected family members through the same bloodline (either maternal or paternal), early onset of disease, an excess of bilateral disease, an association with ovarian cancer (at any age), and occurrence of BC in males. Genetic testing confirms the diagnosis and allows better management of people at high risk of developing BC and/or OC. The management strategies include surveillance, surgical options and chemoprevention, and accurate treatment of BC and OC in mutation carriers, but the treatment guidelines are still under debate. Studies of cohorts of BRCA1 and BRCA2 mutation carriers are underway in an effort to develop targeted cancer prevention strategies.
Last update: October 2004