The association between non-breast and ovary cancers and BRCA mutation in first- and second-degree relatives of high-risk breast cancer patients: a large-scale study of Koreans.

Background: As a large-scale study of Koreans, we evaluated the association between BRCA mutation and the prevalence of non-breast and ovary cancers in first- and second-degree relatives of high-risk breast cancer patients.

Methods: We organized familial pedigrees of 2555 patients with breast cancer who underwent genetic screening for BRCA1/2 in Samsung Medical Center between January 2002 and May 2018. Families with a member that had a history of cancer other than of the breast or ovary were regarded positive for other primary cancer.

Results: The median age of the population was 40 years (range, 19 to 82 years). BRCA mutation was detected in 377 (14.8%) of the patients. The BRCA-positive group had a higher frequency of family history of breast or ovarian cancer ( p  <  0.001), bilateral breast cancer ( p  = 0.021), and the male gender ( p  = 0.038). There were 103 (27.3%) patients who had multiple risk factors in the BRCA-positive group, while there were 165 (7.6%) patients who had multiple risk factors in the BRCA-negative group ( p  <  0.001). BRCA mutation was detected in 215 (11.7%) of the 1841 families without history of other primary cancers. Among the 714 families with histories of other primary cancers, 162 (22.7%) had BRCA mutation, and this was significantly more frequent ( p  < 0.001) than in those without a history. The occurrence of other primary cancers in families of high-risk patients was associated with a younger age at diagnosis ( p  = 0.044), bilateral breast cancer ( p  = 0.006), and BRCA mutations (p < 0.001). The most common site for the occurrence of another type of primary cancer was the stomach. In the BRCA-positive group, the proportional incidences of stomach, pancreas, colorectal, lung, and uterine cancer were 13.8, 4.0, 7.7, 8.8, and 5.0%, respectively; these were all relatively higher than those in the BRCA-negative group.

Conclusions: We confirmed that BRCA mutation was associated with having multiple risk factors and an increased prevalence of non-breast and ovary cancers in first- and second-degree relatives of high-risk breast cancer patients. Due to the possibility of inherited cancer risk, genetic counseling with options for risk assessment and management should be provided to both patients and families of BRCA mutation carriers.