ESTRO 2025 - Abstract Book

S568

Clinical - Breast

ESTRO 2025

3313

Digital Poster Impact of radiotherapy heart dose in HER 2 + breast cancer patients undergoing chemotherapy with trastuzumab pertuzumab: a real life multicentre study Edy Ippolito 1,2 , Valeria Masiello 3 , Sara De Matteis 4 , Paola Anselmo 5 , Fabio Marazzi 3 , Salvatore Minuti 2 , Marco Donato 6 , Francesco Pantano 7,8 , Martina Benincasa 2 , Marco Mazzotta 9 , Giuliana D'Auria 10 , Matteo Vergati 10 , Paola Martucci 1 , Guenda Meffe 1 , Michele Fiore 1,2 , Angela Sardaro 4 , Maria Antonietta Gambacorta 3,11 , Sara Ramella 1,2 1 Radiation Oncology, Fondazione Policlinico Campus Biomedico, Rome, Italy. 2 Research Unit Radiation Oncology, Università Campus Bio-Medico, Rome, Italy. 3 Radioterapia Oncologica, Dipartimento Di Diagnostica Per Immagini e Radioterapia Oncologica, Fondazione Policlinico Universitario "A. Gemelli", Rome, Italy. 4 Radiation Oncology Unit, Dipartimento di Oncoematologia, Ospedale "Vito Fazzi", Lecce, Italy. 5 Radiotherapy Oncology Centre, "S. Maria" Hospital, Terni, Italy. 6 Medical Oncology, Fondazione Policlinico Campus Biomedico, Roma, Italy. 7 Medical Oncology, Fondazione Policlinico Campus Biomedico, Rome, Italy. 8 Research Unit Medical Oncology, Università Campus Bio Medico, Rome, Italy. 9 Medical Oncology Unit, Ospedale Sandro, Rome, Italy. 10 Medical Oncology, Ospedale Sandro Pertini, Rome, Italy. 11 Istituto di Radiologia, Università Cattolica del Sacro Cuore, Roma, Italy Purpose/Objective: The combination of trastuzumab pertuzumab and radiotherapy is considered safe in both loco-regional and metastatic setting. This contemporary multicentre real life study aims to specifically analyze if there is any increased cardiac toxicity in relation to breast radiotherapy, especially when higher heart dose are delivered Material/Methods: Patients with HER-2 positive stage II-III breast cancer treated with either neoadjuvant adjuvant chemotherapy who received the combination of pertuzumab and trastuzumab were identified. All patients underwent breast surgery and received a comprehensive cardiologic evaluation at baseline and after neoadjuvant and/or adjuvant treatment. Patients who received postoperative radiotherapy constituted a case cohort (RTC), whereas those treated without radiotherapy accounted for control cohort (CC). Left ventricular ejection fraction (LVEF) was measured via echocardiography at baseline and during follow-up. In patients undergoing radiotherapy heart and left anterior descending artery doses were collected. Cardiologic adverse events were defined as decreased LVEF (reduction to ≤50% or more than 10% from baseline). Differences between groups were assessed by means of Pearson’s chi square test for categorical data and Mann-Whitney U test for continuous variables. chemotherapy plus trastuzumab pertuzumab combination. Among the whole patients population 66.7% patients received neoadjuvant chemotherapy , 71.4% antracycline based chemotherapy. Overall LVEF impairment was observed in 12 patients (7.7%), 8 (8.3%) receiving radiotherapy. In patients who received postoperative radiotherapy regional nodal irradiation (RNI) was administered in 30.3% and internal mammary chain (IMC) was treated in 11.6%patients. The mean dose delivered to heart and LDA was 2.99 Gy (SD: 1.9) and 5.47 Gy (SD 3.9) respectively. Mean heart dose was higher in patients treated to the IMC (3.97Gy vs 2.58 Gy; p=0.003). No difference in LVEF reduction was observed between patients treated with radiotherapy or not (p= NS, see Table 1 for details). Results: The study collected data for a total of 155 patients (96 RTC, 59 CC) from 5 italian centres who received