Effect of Breast Conservation Therapy vs Mastectomy on Overall Survival and Breast Cancer-Specific Survival Among Men With Stage I-II Breast Cancer: Analysis of SEER, 2000-2018

This population-based cohort study of 1369 patients with male breast cancer found that compared with mastec-tomy group,breast conservation therapy is at least equivalent to mastectomy. The study was based on the SEER database and a propensity score-matched analysis. Background: Male breast cancer is a rare malignant tumor, and outcomes of breast conservation therapy (BCT) are currently lacking. Method: The retrospective, population-based cohort study included 1369 stage I-II (T1-2 N0-1 M0) male breast cancer patients from the SEER database (2000-2018). The patients were grouped in two groups: BCT group and mastectomy group, according to surgical and radiation therapy. Kaplan-Meier method and univariable Cox proportional hazard analysis were used to compare overall survival (OS) and breast cancer-specific survival (BCSS) bet ween t wo treatment groups. Propensity score matching (PSM) was performed to balance the confounding factors. Results: Of the 1369 men, 97 (7%) patients received BCT, 1272 (93%) received mastectomy alone. The 5-and 10 -year OS rates were 92.3% and 80.7% for BCT group compared with 80.4% and 61.4% for mastectomy group. The 5 -and 10-year BCSS rates were 96.5% and 93.9% for patients undergoing BCT, as compared with 93.1% and 84.4% for patients undergoing mastectomy. Compared with mastectomy group, BCT group showed improved OS (hazard ratio [HR], 0.294; 95% CI 0.138-0.623, P = .002) and BCSS (hazard ratio [HR], 0.182; 95% CI 0.040-0.820, P = .027). Of the 791 patients with T1 stage, BCT showed insignificant association with OS (hazard ratio [HR], 0.555; 95% CI 0.207-1.488, P = .242) and BCSS (hazard ratio [HR], 1.217; 95% CI 0.171-8.675, P = .844). Conclusion: The results of this cohort study suggest that BCT is at least equivalent to mastectomy in male breast cancer patients. The underlying mechanism of this association needs further research.