Prior Cancer among Men Diagnosed with Breast Cancer is Associated with Worse Overall Survival but Equivalent Breast Cancer-Specific Survival.

Background: Men newly diagnosed with breast cancer (BC) who have survived prior cancer are often excluded from clinical trials, despite limited evidence on how prior cancer impacts BC outcomes. Understanding survival of those with prior cancer is crucial for trial sponsors and investigators to make informed eligibility decisions. Using Surveillance, Epidemiology, and End Results (SEER) data, we investigated the impact of prior cancer on survival in men diagnosed with BC between 2011 and 2015. Methods: We evaluated the prevalence of prior cancer of a different type in adult men with BC and analyzed its effects on overall and BC-specific survival using Cox models and the Fine and Gray method to account for competing risks of death. Models adjusted for covariates including patient, tumor, and treatment factors. Results: Among 1,923 men with BC, 241 (12.5%) had a prior cancer of different type. There were 904 deaths from any cause including 365 from BC. Median overall survival was 10.1 years. Adjusted models demonstrated worse overall survival for men with prior cancer (HR=1.3, 95% CI: 1.1, 1.6) but no statistically significant difference in BC-specific survival (sdHR=0.9, 95% CI: 0.7, 1.4) between the groups. Conclusions: Despite worse overall survival, men with prior cancer did not have worse BC-specific survival, suggesting their inclusion in trials is unlikely to introduce bias in BC-specific survival. Implications for Cancer Survivors: Including men with prior cancer in trials may enhance trial accrual, inclusivity, and generalizability, critical aspects of research studies for this rare cancer in which accrual is already a challenge.