Outcomes of Postoperative Radiotherapy in Male Breast Cancer Patients: A Population-Based Analysis

Abstract

<h3>Purpose/Objective(s)</h3> Male breast cancer is rare, the treatment recommendations are typically extrapolated from clinical trials enrolling female breast cancer patients. The utilization of postoperative radiotherapy (PORT) and its impact on outcomes in male breast cancer patients has not been determined. In our study, we aimed to evaluate the role of postoperative radiotherapy for male breast cancer patients with stage I-III. <h3>Materials/Methods</h3> Male breast cancer patients diagnosed with stage I-III from 2010 to 2016 were selected from the Surveillance, Epidemiology, and End Result (SEER) database. Two cohorts were then created based on the PORT use. The two groups were compared based on demographic (age, race, marital status), tumor (stage, grade, lymph node status, ER/PR/HER2 status) as well as treatment characteristics (surgery type, chemotherapy). The Chi-square test was used to assess differences between treatment groups. The 1:1 propensity score matched (PSM) method was adopted to balance baseline characteristics. Kaplan–Meier curves were used to evaluate the impacts of PORT on survival. The effect of PORT on overall survival (OS) was evaluated using the Kaplan-Meier method and log-rank tests. Univariate and multivariate Cox analyses were used to analyze the factors associated with survival. <h3>Results</h3> Among 2636 patients, 29.1% (766) underwent PORT while the non-postoperative radiotherapy (non-PORT) group contained 70.9% (1870). After PSM, a total of 1242 patients were enrolled in this analysis, including 621 patients in the PORT group and 621 patients in the non-PORT group. Kaplan-Meier and the multivariate survival analysis demonstrated that the PORT group presented with a better prognosis compared to the non-PORT group (after PSM, 5y-OS 75.8% vs.67.6%; p=0.046). On multivariate analysis, there was a significant association between grade III/IV tumors, advanced stage, positive lymph node status, receipt of mastectomy, and radiotherapy and breast cancer death (p<0.05). After controlling for grade, stage, lymph node status, patients who underwent lumpectomy and PORT gained a better survival (5y-OS lumpectomy+PORT vs. mastectomy+PORT vs. mastectomy+non-PORT vs. lumpectomy+Non-PORT: 84.6% vs.71.8% vs.75.8% vs.52.1%; p<0.001). <h3>Conclusion</h3> PORT is associated with a significant survival advantage in OS. Lumpectomy with PORT may become a better option in appropriately selected men with breast cancer.