Increased risk of pancreatic, thyroid, prostate and breast cancers in men with a family history of breast cancer: A population‐based study

Abstract The association between a family history of breast cancer (FHBC) in female first‐degree relatives (FDRs) and cancer risk in men has not been evaluated. This study aimed to compare the risks of overall and site‐specific cancers in men with and without FHBC. A population‐based study was conducted with 3 329 106 men aged ≥40 years who underwent national cancer screening between 2013 and 2014. Men with and without FHBC in their female FDRs were age‐matched in a 1:4 ratio. Men without FHBC were defined as those without a family history of any cancer type in their FDRs. Data from 69 124 men with FHBC and 276 496 men without FHBC were analyzed. The mean follow‐up period was 4.7 ± 0.9 years. Men with an FHBC in any FDR (mother or sister) had a higher risk of pancreatic, thyroid, prostate and breast cancers than those without an FHBC (adjusted hazard ratios [aHRs] (95% confidence interval [CI]): 1.35 (1.07‐1.70), 1.33 (1.12‐1.56), 1.28 (1.13‐1.44) and 3.03 (1.130‐8.17), respectively). Although an FHBC in any one of the FDRs was not associated with overall cancer risk, FHBC in both mother and sibling was a significant risk factor for overall cancer (aHR: 1.69, 95% CI:1.11‐2.57) and increased the risk of thyroid cancer by 3.41‐fold (95% CI: 1.10‐10.61). FHBC in the mother or sister was a significant risk factor for pancreatic, thyroid, prostate and breast cancers in men; therefore, men with FHBC may require more careful BRCA1/2 mutation‐related cancer surveillance.