ESTRO 2025 - Abstract Book

S455

Clinical - Breast

ESTRO 2025

Male breast cancer (BC) accounts for 1% of all BC diagnoses and is characterized by distinct clinicopathologic features, often reflecting and/or driving more unfavorable clinical outcomes as compared to female BC, thus posing impelling clinical challenges 1 . Adjuvant radiation treatment (RT) is one of them 2 . Material/Methods: We included a large monocentric retrospective cohort of male patients with BC diagnosis treated at Istituto Oncologico Veneto - Padova from 1988 to 2024. We collected clinical and long- term follow-up data, analyzed with methods of descriptive statistics.

Results:

We collected data of 161 patients (pts) treated across more than 35 years of experience. 144 patients presented with stage I-III BC at diagnosis and were included in this analysis. 21.3% of patients harbored a germline pathogenetic mutation in BRCA1, BRCA2 or PALB2 genes (respectively, 1.3%, 17.3% and 2.7%, among tested patients) Our male BC population was enriched for HR+/HER2- subtype (n=134, 93% vs HER2+, n=10, 7% vs triple-negative n=0, 0%). Of 144 patients, 54 were candidate for complementary RT by stage (Stage II or III). Of these, 15% did not undergo RT because of concurrent cardiological comorbidities, advanced age, poor performance status or patient refusal. The techniques included are VMAT, IMRT, 2D and 3D. Details regarding specific treatment patterns and dosimetry are listed in table 1. Overall, RT was well tolerated, with only grade 1 or grade 2 skin toxicity events (26.1% and 4.3% of patients, respectively). No cardiotoxicity has been reported, moreover we did not observe radiation pneumonitis nor lung fibrosis. Finally, median follow up was 58 months. 10-years recurrence rate was 62.5% in the untreated subgroup (12.5% local and 50% distance recurrence) and 39.1% in the treated subgroup (6.5% local and 32.6% distance recurrence); median IDFS and OS in the untreated subgroup were 44 and 79 months, respectively, in the treated subgroup IDFS was 53 months and OS was not reached.