Impact of adjuvant radiotherapy in patients with male breast cancer: a multicenter international analysis

Background 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 impact of different treatment factors, in particular, postoperative radiation therapy (RT) on long-term outcomes. Patients and methods Seventy-one patients with male breast cancer treated in five closely cooperating institutions between 2003 and 2019 were analysed. Results Almost all patients (95%) underwent surgical resection. 42 (59%) patients received chemotherapy, 59 (83%) patients 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%, while 5-year progression-free survival (PFS) and 5-year overall survival (OS) were 62% and 96%, respectively. There was a lower rate of relapses following adjuvant RT (19% vs. 32%, p=.02) without in-field relapse after postoperative RT (0%) vs. 10% in patients without RT (p=.02). In the multivariate analysis performed, hormonal therapy administration was found to have a possible significant impact on LC and PFS. Administration of adjuvant RT and stage impact PFS. In patients who received RT, there were no grade 3/4 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 impact on LC and PFS.