ESTRO 2025 - Abstract Book

S2405

Interdisciplinary – Other

ESTRO 2025

3889

Digital Poster High Quality Assurance in Re-irradiation with Proton Therapy: the cumulative dose. Report on 62 patients treated at IEO, IRCCS, Milan, Italy Annamaria Ferrari 1 , Floriana Pansini 2 , Stefania Comi 3 , Marco Liotta 3 , Gaia Piperno 1 , Stefania Volpe 1 , Giulia Marvaso 1 , Samantha Dicuonzo 1 , Federico Mastroleo 1 , Giovanni Carlo Mazzola 1 , Luca Bergamaschi 1 , Maria Giulia Vincini 1 , Mattia Zaffaroni 1 , Karl Amin 1 , Federico Gagliardi 1 , Federica Cattani 3 , Roberto Orecchia 4 , Barbara Alicia Jerczek-Fossa 1 , Daniela Alterio 1 1 Radiation therapy department, European Institute of oncology, Milan, Italy. 2 Medical Physics, European Institute of oncology, milan, Italy. 3 Medical Physics, European Institute of oncology, Milan, Italy. 4 Scientific Direction, European Institute of oncology, Milan, Italy Purpose/Objective Re-irradiation (reRT) is a challenging scenario in the field of proton therapy (PT). The precise evaluation of cumulative doses (CD) obtained adding previous and the current treatment plans is a crucial step to quantify the risk of side effects. Aim of this work was to report the modality of CD calculation used for patients treated with PT at our center.

Material/Methods

All patients treated with reRT from November 2023 to 30 October 2024 were reviewed. The previous treatment plans, when available, was retrived and classified as 1) DICOM files or 2) paper documentation. For patients with available DICOM treatment plans, the summed dose was evaluated according to 4 methods: 1) quantitative maximum summed dose (worst case scenario); 2) qualitative slice-by-slice evaluation; 3) Isodose line transfer; 4)