Evaluating high-risk breast cancer surveillance outcomes in BRCA mutation carriers.

BACKGROUND: Long-term outcome on breast cancer surveillance in BRCA mutation carriers are limited, especially in Asian populations where uptake of preventive surgery is low. METHODS: We conducted a retrospective cohort study of 722 female BRCA1 and BRCA2 mutation carriers enrolled between January 2007 and December 2024 in the Hong Kong Hereditary Breast Cancer Family Registry. Of these, 702 (97.2%) underwent structured high-risk surveillance comprising biannual clinical breast examination and alternating 6-monthly breast magnetic resonance imaging and mammography or digital breast tomosynthesis with ultrasonography. The outcomes were breast cancer detection rate, stage, nodal status, interval cancer occurrence, and breast cancer–specific mortality. RESULTS: Risk-reducing mastectomy was undertaken by 90 out of 722 carriers (12.5%). Surveillance detected 64 breast cancers during 4,398 imaging sessions (detection rate 1.5%). Most cancers (89.1%) were diagnosed at stage 0 or I, and 95.3% were node- negative. Interval cancers were uncommon. Among 304 carriers initially free of breast cancer who later developed the disease (n = 26), no breast cancer–specific death occurred. Overall, breast cancer–specific mortality in the cohort was 2.4%, with most deaths due to ovarian cancer with a median follow-up of 39.1 months (range, 6-212.3). Longer term follow-up is warranted. CONCLUSIONS: In this first Asian surveillance cohort of BRCA mutation carriers, prophylactic mastectomy uptake was low, yet structured screening enabled early-stage detection and minimal interval cancer. Surveillance should be considered as a key management strategy, with preventive surgery options individualized and cost-effectiveness evaluated.