Impact of Adjuvant Radiation Therapy in Patients With Male Breast Cancer: A Multicenter International Analysis

PURPOSE: Breast cancer in men accounts for approximately 1% of all breast cancers. Breast cancer trials have routinely excluded men. The aim of this analysis was to determine the effect of different treatment factors, in particular, postoperative radiation therapy (RT) on long-term outcomes. METHODS AND MATERIALS: Seventy-one patients with male breast cancer treated in 5 closely cooperating institutions between 2003 and 2019 were analyzed. RESULTS: Almost all patients (95%) underwent surgical resection. Forty-two patients (59%) received chemotherapy, and 59 (83%) received adjuvant hormonal therapy. Of the 71 patients, 52 (73%) were treated with RT. The rate of recurrence was 20% in the whole cohort, with a locoregional recurrence rate of 3%. In the entire group, the 5-year local control (LC) was 95%, whereas 5-year progression-free survival (PFS) and 5-year overall survival (OS) were 62% and 96%, respectively. There was a lower rate of relapses after adjuvant RT (19% vs 32%, P = .05) without in-field relapse after postoperative RT (0%) versus 10% in patients without RT (P = .02). In the multivariate analysis performed, hormonal therapy administration was found to have a possible significant effect on LC and PFS. Administration of adjuvant RT and stage affect PFS. In patients who received RT, there were no grade 3 or 4 acute toxicities. CONCLUSIONS: Adjuvant RT is an effective and safe treatment for male breast cancer patients with no infield relapses and better PFS. Hormonal therapy administration was found to have a possible effect on LC and PFS.