Genetics and Breast Cancer
Genetic mutations and hereditary conditions play a significant role in increasing breast cancer risk. The most well-known are mutations in the BRCA1 and BRCA2 genes, which substantially raise the likelihood of developing breast and ovarian cancer compared to the general population:
Both are tumour suppressor genes important for repairing damaged DNA. Harmful inherited mutations impair their function, increasing cancer susceptibility.
Women with BRCA1 mutations have an estimated 44–78% lifetime risk of breast cancer, while those with BRCA2 mutations have about a 31–56% risk, far above the general population risk of ~12%.
BRCA1-related breast cancers often tend to be triple-negative breast cancers, which are more aggressive and may require different treatment strategies.
Women with BRCA mutations face a higher chance of contralateral breast cancer (cancer in the opposite breast) after a primary diagnosis.
Mutations in other genes like TP53 (Li-Fraumeni syndrome), PALB2, CHEK2, ATM, and PTEN (Cowden syndrome) also raise breast cancer risk, though usually to a lesser extent than BRCA mutations.
Genetic testing is recommended for individuals with a strong family history of breast, ovarian, pancreatic, or prostate cancer, early-onset breast cancer (diagnosed before age 50), triple-negative breast cancer diagnosed before age 60, multiple family members with breast or related cancers, Ashkenazi Jewish or other high-risk ancestry groups where mutations are more common.
Results inform personalised screening strategies, preventive measures (like prophylactic surgery), and treatment planning.