Hereditary Cancer Syndromes: When to Test and Surveillance Guidelines

Indications for Genetic Testing

NCCN guidelines recommend genetic testing for patients with: breast cancer diagnosed at age 50 or younger, triple-negative breast cancer at any age, ovarian/fallopian tube/primary peritoneal cancer, male breast cancer, pancreatic cancer with any family history, metastatic prostate cancer (per NCCN and Philadelphia Consensus 2024), colorectal or endometrial cancer diagnosed before age 50 or with mismatch repair deficiency on IHC/MSI testing, and any patient with 2 or more first-degree relatives with BRCA-associated or Lynch-associated cancers. The 2024 ASCO guideline update endorses population-based testing (regardless of personal or family history) for BRCA1/2 and Lynch syndrome genes in all adults, supported by the PREVALENCE study showing 50% of mutation carriers have no family history meeting current testing criteria.

BRCA1/2: Risk Assessment and Management

BRCA1 carriers have a cumulative breast cancer risk of 72% and ovarian cancer risk of 44% by age 80 (Kuchenbaecker et al., 2017, JAMA). BRCA2 carriers have 69% breast and 17% ovarian cancer cumulative risks. Surveillance for unaffected carriers includes annual breast MRI starting at age 25-29 and annual mammography starting at age 30 (alternating at 6-month intervals). Risk-reducing bilateral salpingo-oophorectomy (RRSO) by age 35-40 for BRCA1 and age 40-45 for BRCA2 reduces ovarian cancer risk by 80% and breast cancer risk by 50% when performed premenopausally. Risk-reducing mastectomy reduces breast cancer risk by 90-95% but is a personal decision. PARP inhibitor therapy (olaparib 300 mg BID) in the OlympiA trial reduced invasive disease recurrence by 42% (HR 0.58) in high-risk BRCA-mutant early breast cancer.

Lynch Syndrome: Screening and Surveillance

Lynch syndrome (germline MLH1, MSH2, MSH6, PMS2, or EPCAM mutations) carries colorectal cancer risks of 40-80% for MLH1/MSH2, 10-22% for MSH6, and 15-20% for PMS2 by age 70. Endometrial cancer risk is 25-60% for MLH1/MSH2 carriers. Universal tumor testing with IHC for mismatch repair proteins or MSI testing is now recommended for all newly diagnosed colorectal and endometrial cancers (NCCN 2024). Surveillance includes colonoscopy every 1-2 years beginning at age 20-25 (or 2-5 years before youngest CRC diagnosis in family). Aspirin 600 mg daily reduced CRC incidence by 63% in Lynch syndrome carriers at 10-year follow-up in the CaPP2 trial (HR 0.37, 95% CI 0.18-0.78), with the optimal dose being investigated in the CaPP3 trial (100 mg, 300 mg, or 600 mg).