Cancer risk in relatives of BRCA1/2 pathogenic variant carriers in a large series of unselected patients with breast cancer

Objective: The spectrum and risk of cancer in relatives of BRCA1/2 pathogenic variant carriers in the Chinese population have not been established.Methods: A family history of cancer in 9903 unselected breast cancer patients was retrospectively analyzed. BRCA1/2 status was determined for all patients and relative risks (RRs) were calculated to evaluate cancer risk in relatives of the patients.Results: The incidences of breast cancer in female relatives of BRCA1 carriers, BRCA2 carriers, and non-carriers were 33.0%, 32.2%, and 7.7%, respectively. The corresponding incidences of ovarian cancer were 11.5%, 2.4%, and 0.5%, respectively. The incidences of pancreatic cancer in male relatives of BRCA1 carriers, BRCA2 carriers, and non-carriers were 1.4%, 2.7%, and 0.6%, respectively. The corresponding incidences of prostate cancer were 1.0%, 2.1%, and 0.4%, respectively. The risks of breast and ovarian cancers in female relatives of BRCA1 and BRCA2 carriers were significantly higher than female relatives of non-carriers (BRCA1: RR = 4.29, P < 0.001 and RR = 21.95, P < 0.001; BRCA2: RR = 4.19, P < 0.001 and RR = 4.65, P < 0.001, respectively). Additionally, higher risks of pancreatic and prostate cancers were noted in male relatives of BRCA2 carriers than non-carriers (RR = 4.34, P = 0.001 and RR = 4.86, P = 0.001, respectively). Conclusions: Female relatives of BRCA1 and BRCA2 carriers are at increased risk for breast and ovarian cancers, and male relatives of BRCA2 carriers are at increased risk for pancreatic and prostate cancers.