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Introduction: Male breast cancer (MBC) is a rare malignancy, accounting for about 1% of all breast cancers. Treatment guidelines are largely extrapolated from female breast cancer (FBC) studies, with limited MBC-specific evidence. This study evaluates the impact of postmastectomy radiotherapy (PMRT) on survival outcomes in MBC. Methods: We conducted a retrospective cohort study using the SEER database (2004-2015) and the Shanghai Jiao Tong University Breast Cancer Data Base (SJTUBCDB). Included were MBC patients with T1-2N1M0 disease after mastectomy. Inverse probability of treatment weighting (IPTW) was used to balance baseline characteristics. Overall survival (OS), breast cancer-specific survival (BCSS), and disease-free survival (DFS) were compared between PMRT and non-PMRT groups. Competing risks were accounted for in BCSS analysis using the Fine-Gray subdistribution hazard model. Subgroup analyses were based on tumor size, lymph node involvement, and hormone receptor status. Results: Of 714 eligible SEER patients, 33.9% received PMRT. PMRT was associated with improved OS (HR 0.79, 95% CI 0.53-0.94), especially in patients with T2 tumors, 2-3 positive lymph nodes, or negative progesterone receptor (PR) status. Competing risk analysis confirmed no significant difference in BCSS (subdistribution HR 0.79, 95% CI 0.44-1.42). No significant difference in BCSS was observed. In the SJTUBCDB cohort (n=50), similar directional trends were noted: PMRT was linked to better OS and DFS in high-risk subgroups, particularly in Luminal B subtypes and patients with T2 tumors or multiple involved lymph nodes. Conclusion: PMRT was associated with improved OS in selected MBC patients with high-risk features such as larger tumors or PR-negative disease. The consistent findings from SEER and SJTUBCDB support the use of PMRT in high-risk MBC patients and highlight the need for personalized treatment strategies and prospective trials.
Wang et al. (Fri,) studied this question.