Sex Disparities in Breast Cancer Survival According to Clinical Treatment Score Post-5 Years (CTS5) Risk Stratification.

[PURPOSE] The role of the Clinical Treatment Score post-5 years (CTS5) in male breast cancer (MBC) remains unclear. This study aimed to investigate the characteristics and prognosis of CTS5 between MBC and female breast cancer (FBC).

[MATERIALS AND METHODS] Patients diagnosed with human epidermal growth factor receptor 2-negative/estrogen receptor-positive breast cancer between 2010 and 2015 were identified from the Surveillance, Epidemiology, and End Results (SEER) database. The chi-square test, Kaplan-Meier analysis, and multivariate Cox proportional hazard model were used for statistical analysis.

[RESULTS] This study included 169,869 patients, comprising 168,422 (99.1%) FBC and 1,447 (0.9%) MBC patients. More MBC patients had intermediate risk (IR)/high risk (HR) disease compared to FBC patients (17.7% vs. 8.7%, p < 0.001). MBC patients had an inferior overall survival (OS) but similar breast cancer-specific survival compared to those with FBC. Sensitivity analyses showed that sex was an independent prognostic factor associated with OS but not breast cancer-specific survival (BCSS) in both the low-risk (LR) and IR/HR cohorts. Those with MBC exhibited significantly worse OS (p < 0.001) than FBC patients in both cohorts. In MBC patients, those with IR/HR disease had significantly worse OS (p < 0.001) and BCSS (p < 0.001) compared to those with LR disease. For FBC patients, the IR/HR group had also significantly worse OS (p < 0.001) and BCSS (p < 0.001) compared to the LR group.

[CONCLUSION] Our findings highlight critical differences in clinical characteristics, treatment patterns, and outcomes between MBC and FBC, suggesting the need for sex-tailored approaches in breast cancer management.