ESTRO 2025 - Abstract Book

S1702

Clinical - Sarcoma & skin cancer & malignant melanoma

ESTRO 2025

gateway for standard treatments, providing a clear and controlled environment to test and compare the effects of FLASH radiotherapy against conventional techniques.

Keywords: VHEE, UHDR, flash radiotherapy

References: 1. Giannini Noemi [et al.], Electron FLASH radiotherapy in vivo studies. A systematic review. Front Oncol. 2024 Apr 9;14:1373453. doi: 10.3389/fonc.2024.1373453. PMID: 38655137; PMCID: PMC11035725 2. Bourhis Jean [et al.], Treatment of a first patient with FLASH-radiotherapy. Radiother Oncol. 2019 Oct;139:18-22. doi: 10.1016/j.radonc.2019.06.019. Epub 2019 Jul 11. PMID: 31303340 3. Likhacheva Anna [et al.], Definitive and Postoperative Radiation Therapy for Basal and Squamous Cell Cancers of the Skin: Executive Summary of an American Society for Radiation Oncology Clinical Practice Guideline. Pract Radiat Oncol. 2020 Jan-Feb;10(1):8-20. doi: 10.1016/j.prro.2019.10.014. Epub 2019 Dec 9. PMID: 31831330

2923

Digital Poster Response analysis for radiotherapy and radiotherapy with hyperthermia in patients with metastatic melanoma oligoprogression Aneta Maria Borkowska 1,2 , Paulina Chmiel 1 , Piotr Rutkowski 1 , Maria Telejko 2 , Mateusz Jacek Spałek 2 1 Department of Soft Tissue/Bone Sarcoma and Melanoma, Maria Sklodowska-Curie National Research Institute of Oncology, Warsaw, Poland. 2 Department of Radiotherapy I, Maria Sklodowska-Curie National Research Institute of Oncology, Warsaw, Poland Purpose/Objective: The efficacy of local radiotherapy in the treatment of oligoprogressive metastatic melanoma (MM) has been demonstrated. However, data on long-term outcomes and clinical evaluation of patients are still lacking. The aim is to evaluate responses, time to response (TTR), and duration of response (DOR) for RTH and RTH with hyperthermia (HT) in patients with oligoprogressive metastatic melanoma (MM) under systemic treatment. Material/Methods: Patients treated at referral center between 2018 and 2023 were included. Oligoprogression was defined as up to five progressive metastases. Systemic treatment included immunotherapy and BRAF/MEK inhibitors, and RTH was employed as the sole method or with HT. Response to RTH in different evaluation intervals according to response evaluation criteria in solid tumors 1.1 (RECIST1.1), TTR and DOR were analyzed. Factors that may influence DOR were evaluated. Results: The 156 patients were included, 82 pts had RTH+HT while 74 had RTH only, and 184 lesions were irradiated. Median follow-up was 17 months. Immunotherapy was used in 82.7% and BRAF/MEK inhibitors in 17.3% of patients. Median total dose of RTH was 32 Gy (10-50 Gy), and the median biologically effective dose (BED) was 108.8 Gy. There were 27 (14.7%) complete responses (CR) and 62 (33.7%) partial responses (PR) at the last follow-up. Thus, the overall response rate was 48.3%. CR increased from 2.2% to 14.7% at 1.4 and 13.3 months following RTH. Only two patients who initially achieved CR had PD (recurrence of the irradiated lesion) at the last follow-up. TTR was 4.2 months, and DOR was 38.5 months for pts with RTH only. TTR was 2.7 months, and DOR was not reached at the time of the analysis for pts with RTH+HT. There were no statistical differences between groups for TTR (p=0.13) and DOR (p=0.62). Total dose higher then median (p=0.1), and systemic treatment (immunotherapy vs. BRAF/MEK inhibitors; p=0.57) did not influence DOR. Patients with BED lower to median exhibited significantly inferior DOR outcomes (p=0.006).