ESTRO 2025 - Abstract Book

S591

Clinical - Breast

ESTRO 2025

3632

Digital Poster Multicentric long-term analysis of 307 male breast cancer patients

Riccardo Ray Colciago 1,2 , Pierfrancesco Franco 3,4 , Carlotta Giandini 2 , Maria Grazia Carnevale 2 , Alessandra Fozza 5 , Angela Coco 5 , Ruggero Spoto 6 , Lorenza Marino 7 , Sara Lucidi 8 , Fiorenza De Rose 8 , Elisabetta Bonzano 9 , Agnese Prisco 10 , Bruno Meduri 11 , Niccolò Bertini 12 , Icro Meattini 12 , Maria Carmen De Santis 2 1 Medicine and Surgery Department, University of Milan Bicocca, Milan, Italy. 2 Radiation Oncology, Fondazione IRCCS Istituto Nazionale dei Tumori, Milano, Italy. 3 Translational Medicine (DIMET), University of Eastern Piedmont, Novara, Italy. 4 Radiation Oncology, 'Maggiore della Carità' University Hospital, Novara, Italy. 5 Radiation Oncology, IRCCS Ospedale Policlinico San Martino, Genova, Italy. 6 Radiotherapy and Radiosurgery, IRCCS Humanitas Research Hospital, Milano, Italy. 7 Servizio di Radioterapia, Humanitas Istituto Clinico Catanese, Misterbianco, Italy. 8 Radiation Oncology, APSS, Trento, Italy. 9 Radiation Oncology, Fondazione IRCCS Policlinico San Matteo and University of Pavia, Pavia, Italy. 10 Radiation Oncology, University Hospital of Udine, ASUIUD, Udine, Italy. 11 Radiation Oncology, University Hospital of Modena, Modena, Italy. 12 Radiation Oncology & Breast Unit, Florence University Hospital, Azienda Ospedaliero Universitaria Careggi, Firenze, Italy Purpose/Objective: Male breast cancer is rare, and treatment recommendations are often informed by evidence in female breast cancer. This multicentre study evaluates long-term outcomes and prognostic factors in male breast cancer patients. Material/Methods: Data from 307 male breast cancer patients treated between 2005 and 2023 across 10 oncology centres were retrospectively analysed. Patients with confirmed breast cancer were included. Collected data comprised patient demographics, comorbidities, tumour characteristics, and treatment modalities (surgery, systemic and radiation therapies). Kaplan-Meier and Cox regression analyses were conducted to assess loco-regional control (LC), disease free (DFS), and overall survival (OS) and to explore prognosticators, with particular attention to radiation therapy outcomes. Results: With a median follow-up of 65 months (range 1–224), BRCA1/2 mutations were identified in 41 patients (13.5%) among the 67.5% tested. Most patients (83.5%) presented with pT1-2 tumours, while 10.7% had pT4 disease. Negative nodal status was observed in 45%, while 7.1% had pN3 disease. De novo metastases were present in 7 patients. Ductal carcinoma was the predominant subtype (87.7%), and 58% of tumours were grade 1–2. Luminal A, B HER2 + and triple negative subtypes were 107 (34.8%), 164 (53.4%), 23 (7.5%) and 1 (0.3%), respectively. Surgical treatment included mastectomy in 93.5%, with 44.3% undergoing sentinel lymph node biopsy and 42% receiving axillary dissection. Adjuvant chemotherapy was administered to 35.1%, and 32.8% received radiation therapy (median dose: 50Gy; range 28.5–60Gy over 5–30 fractions). Loco-regional recurrence occurred in 30 patients (5.3%), disease relapse in 54 (9.9%), and 81 patients (26.8%) died during follow-up. The median LC, DFS, and OS were 64, 60, and 65 months, respectively, with 5-year rates of 91.7% (LC), 82.5% (DFS), and 83% (OS), as shown in figure. Univariate analysis suggested a trend of increased local recurrence with radiation therapy (HR 2.7, p = 0.053), though this was not significant in multivariate analysis after adjustment for confounding factors. Luminal A-like subtype correlated with improved LC (HR 0.17, p = 0.04) and DFS (HR 0.29, p = 0.01). Positive nodal status predicted worse DFS (HR 3.41, p = 0.01), while older age was associated with reduced OS (HR 1.05/year, p = 0.004).