BRCA Mutations Point to Hereditary Breast and Ovarian Cancer Syndrome
By Lisa Schlager, Facing Our Risk
Although all cancers have a genetic basis, a subset result from an inherited (i.e., germline) mutation that puts a person at increased risk for certain cancers. Unfortunately, the signs of hereditary cancer are often overlooked or misunderstood. Here’s what oncology nurses need to know about BRCA mutations, one of the more common mutations you’ll see in practice.
Facts and Misconceptions
Women who carry a mutation in the BRCA1 or BRCA2 genes are at significantly increased risk for breast and ovarian cancer. People often assume that men are not affected by BRCA mutations, but that’s a misconception. In men, BRCA mutations are associated with increased risk for breast and prostate cancer. BRCA mutations may also cause increased risk for melanoma and pancreatic and other cancers.
Women in the general population face about a 12% lifetime risk of developing breast cancer and a 1.5% chance of ovarian cancer, but that risk increases significantly with a BRCA mutation. Kuchenbaecker et al. found that cumulative lifetime (to age 80) breast cancer risk (https://doi.org/10.1001/jama.2017.7112) was 72% for BRCA1 and 69% for BRCA2 carriers. The risk of contralateral breast cancer in BRCA mutation carriers is two to three times that of women without mutations. For ovarian cancer, the study showed a cumulative lifetime risk of 44% for BRCA1 and 17% for BRCA2 carriers. It’s important to note that fallopian tube and primary peritoneal cancer are often included in the umbrella of ovarian cancer.
Many people don’t realize that a predisposition to “female cancers” can be inherited from one’s mother or father. Certain populations are affected by hereditary cancers in greater numbers. For instance, one in 40 people of Ashkenazi Jewish descent carries a BRCA mutation compared to one in 400 in the general population. But because the Jewish community accounts for only 2% of the U.S. population, you’ll see exponentially more non-Jewish BRCA mutation carriers.
Prevalence estimates for BRCA and other mutations associated with increased cancer risk vary, but it’s fair to say that up to 10% of female breast cancers (especially early onset) and 20% of ovarian cancers result from hereditary factors. In men, up to 40% of breast cancers may be related to BRCA mutations (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1712443), and men with the mutations are up to seven times more likely to get prostate cancer (http://cancerres.aacrjournals.org/content/60/16/4513.long).
Assessment and Genetic Testing
Identifying patients who carry a BRCA mutation is vital to ensure that they are afforded the best treatment or risk-reducing options for breast or ovarian cancer as well as managing risk of other associated cancers. Information about a germline mutation is also helpful in informing relatives of their potential increased cancer risk. See Figure 1 for the signs to look for to identify patients at risk for a hereditary breast and ovarian cancer syndrome.
Several hereditary cancer genes and syndromes have been identified, each with a different set of traits (http://www.facingourrisk.org/understanding-brca-and-hboc/information/hereditary-cancer/other-genes). As such, genetic testing beyond BRCA may be indicated.
If you suspect that a patient’s cancer may be hereditary, national guidelines recommend referral to a genetics expert to ensure that they receive appropriate counseling and testing, if indicated. For more information about hereditary cancer, visit www.facingourrisk.org (http://www.facingourrisk.org).