Abstract
BACKGROUND: Current evidence on risk of prostate cancer following a diagnosis of male breast cancer is limited and guidance for screening in this potentially higher-risk population remainsunclear. Our objective was to quantify prostate cancer risk in men diagnosed with breast cancer. METHODS: We identified men diagnosed with first primary breast cancer between 1988 and 2012 using the Surveillance, Epidemiology and End Results Program registry databases. Men were followed for occurrence of a second primary prostate cancer and secondary outcomes of cancer-specific and overall survival. Stratified analyses were performed by age, breast cancer stage, race, and breast cancer hormone receptor status. Excess risk per 10,000 person-years and standardized incidence ratios (SIR) with 95% confidence intervals (95% CI) were calculated. We used multivaraible Cox proportional hazard models to estimate hazard ratios (HR) and 95% CI for characteristics associated with secondary prostate cancer and survival. RESULTS: From a cohort of 5753 men with breast cancer with median follow up of 4.3 years, we identified 250 cases of second primary prostate cancer. Overall, the incidence of second primary prostate cancer was modestly greater than expected (SIR = 1.12, 95% CI 0.93-1.33), although not statistically significant. Stratified analyses demonstrated associations for men ages 65-74 at the time of breast cancer diagnosis (SIR = 1.34, 95%CI 1.01-1.73), hormone receptor-positive breast cancer (SIR = 1.23, 95%CI 1.11-1.39) or AJCC stage I breast cancer (SIR = 1.36, 95%CI 1.04-1.75) and second primary prostate cancer diagnosis. CONCLUSIONS: The incidence of prostate cancer in men with history of breast cancer is similar to the general population. Men with favorable characteristics of their breast cancer were more likely to develop prostate cancer, possibly due to a lower competing risk of breast cancer mortality.