A BRCA mutation is a mutation in either of the genes BRCA1 and BRCA2. Hundreds of mutations have been identified, some of them cause increased risk of breast cancer, ovarian cancer and other cancers. Instead of a 12 percent lifetime risk of breast cancer, women with high risk BRCA1 or BRCA2 gene mutations may have a risk of up to 60 percent^[1] risk of developing breast cancer. The increased risk of developing ovarian cancer is about 55% for women with high risk BRCA1 mutations and about 25% for women with high risk BRCA2 mutations.^[2]

Cancer risk

Both BRCA1 and BRCA2 are tumor suppressor genes^[3][4] and are involved in DNA repair of double-strand breaks.^[5] The BRCA2 protein also binds to and regulates RAD51 to fix DNA breaks. Mutations in BRCA1 and/or BRCA2 cause decreased stability of the human genome and result in dangerous gene rearrangements that can lead to hematologic cancers.^[5]

Patients carrying heterozygous germline mutations in either the BRCA1 or BRCA2 genes demonstrate highly penetrant breast and ovarian cancer phenotypes. The tumors arising in these patients exhibit loss of heterozygosity (LOH) at the wildtype allele.^[6]

Cancer prevention strategies

Women with a family history of breast and/or ovarian cancer are screened for mutations in their BRCA1 and BRCA2 genes. A number of investigation have been tried or are under investigation reduce cancer risk and improve survival rates.

Prophylactic surgery

Depending on further circumstances prophylactic mastectomy and/or salpingo-oophorectomy may yield a substantial reduction of breast and ovarian cancer risk in BRCA1 and BRCA2 carriers.^[6].

For carriers of high risk BRCA1 mutations prophylactic oophorectomy around age 40 reduces the risk of ovarian and breast cancer and provides significant and substantial long term survival advantage. Earlier intervention does on average not provide any additional benefit but increases risks and adverse effects.

For carriers of high risk BRCA2 mutations oophorectomy around age 40 has only marginal effect on survival, the positive effect of reduced breast and ovarian cancer risk is nearly balanced by adverse effects. The survival advantage is more substantial when oophorectomy is performed together with prophylactic mastectomy.

The effect of preventive mastectomy on overall survival is very small when compared with intensive screening.^{[7] [8]}

Other effects

There is likely little or no effect of a BRCA gene mutation on fertility.^[9]

Evolutionary advantage of BRCA mutations

Several theories assert that BRCA mutations have evolutionary advantages, such as higher intelligence. The Ashkenazi intelligence theory was proposed by Gregory Cochran and asserts that a defect in the BRCA1 gene might unleash neural growth. ^[10]

See also

• Medical genetics of Jewish people

References