BRCA1/2 associated cancer susceptibility: a clinical overview

The most frequently identified genetic cause of breast cancer is the germline mutation of BRCA1 and 2 genes. The carriers of these mutations are at high risk for breast and ovarian cancers and increased risk for pancreatic and prostate cancers. Personal and family history are routinely used to identify individuals at risk for carrying such mutations. Genetic counselling is required to guide them through genetic testing and risk management. Positive testing corresponds to a deleterious mutation, whereas negative testing is considered as uninformative; variants of unknown clinical significance are also classified as uninformative.

The most effective risk reduction strategy involves bilateral prophylactic mastectomy and bilateral salpingo-oophorectomy, eliminating 90% of breast and 97% of ovarian cancer risks, respectively. Before and until such surgery, surveillance with physical examination, mammography and magnetic resonance mammography, starting at 25–30 years of age, are recommended for the early diagnosis of breast cancer; semi-annual surveillance with physical examination, transvaginal ultrasound and serum CA-125 is recommended for women who have not had prophylactic surgery. Carriers diagnosed with breast cancer run a high risk for a new breast primary and this information should be used accordingly. PARP inhibitors is a new class of antineoplastic agents, already approved for advanced BRCA1/2 mutant (germline or somatic) ovarian cancer.

Multigene panel testing may follow a negative BRCA genetic test, often identifying other genetic causes of cancer, expanding its role in oncology. Further adoption of PARP inhibitors, refinement in estimation of BRCA-associated cancer risks and wider population testing, through NGS technology, may become available in the near future.