Prognostic value of Oncotype DX Breast Recurrence Score (RS) in male patients with breast cancer is understudied. We evaluated associations of RS with overall mortality in male patients with breast cancer and compared it with female counterparts.

With a cohort of 848 male and 110,898 female patients with breast cancer identified from the National Cancer Database (2010-2014), we estimated HRs and 95% confidence intervals (CI) for overall mortality associated with RS using Cox regression models. RS was evaluated continuously, as well as by categorization following respective traditional (≤17, 18-30, and ≥31) and TAILORx (≤10, 11-25, and ≥26) cutoffs.

RS was positively associated with mortality in male patients (HR = 1.13; 95% CI, 1.02-1.26 per unit RS increment) up to RS > 21, after which the risk plateaued. Among female patients, mortality began to increase with RS only when RS > 23 (HR = 1.02; 95% CI, 1.01-1.02 per unit of RS increment). The intermediate- (HR = 5.37; 95% CI, 1.79-16.11) and high-risk diseases (HR = 4.28; 95% CI, 1.22-14.97) defined by TAILORx, but not traditional cutoffs established for female patients, were associated with elevated mortality risk in men even after adjustment for demographic, clinical characteristics, and treatments, except chemotherapy.

RS is associated with mortality in male patients with breast cancer at a much lower threshold than that for female patients. Studies are needed to establish specific guidelines for RS thresholds for male patients with breast cancer.