ESTRO 2025 - Abstract Book

S1540

Clinical – Mixed sites & palliation

ESTRO 2025

Conclusion: This study provides unique insights into the adoption of hypofractionated regimens in the treatment of bone metastases, demonstrating variation between treatment centers and a slight increase since the COVID-19 pandemic. Comparable pain response was observed between patients receiving hypofractionated and multiple fraction regimens, suggesting equal palliation in both groups.

Keywords: bone metastases, fractionation, pain response

3043

Digital Poster Personalized by Single Fraction Eight-Gray Palliative SBRT For Bone M+ Pain: the SAINT Study; Single Arm Phase 2 Cohort Analysis for worst prognosis Francesco Cellini 1 , Stefania Manfrida 2 , Silvia Longo 2 , Valeria Masiello 2 , Silvia Chiesa 2 , Gilda Abete 1 , Lana Smiljanic 1 , Elisa Meldolesi 2 , antonella Martino 2 , Gerardina Stimato 2 , Fabio Marazzi 2 , Nicola Dinapoli 2 , Maria Antonietta Gambacorta 1 1 Dipartimento Universitario Diagnostica per immagini, Radioterapia Oncologica ed Ematologia, Università Cattolica del Sacro Cuore, Rome, Italy. 2 Dipartimento di Diagnostica per Immagini, Radioterapia Oncologica ed Ematologia, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, Rome, Italy Purpose/Objective: Palliative Radiotherapy for painful bone metastases represents a crucial clinical, scientific and organizational issue. Intensified, stereotactic radiotherapy (SBRT) is often applied but clear evaluation of result is controversial since most of the experiences are conducted outside clinical trials and clinical benefit is not always univocal. In most of the studies a prognostic score is not applied to stratify patients, although usually suggested as needed. Aim of this single institutional prospective trial is to evaluate the efficacy and safety of an intensified SBRT schedule for patients with painful bone metastases at worst prognosis. (Clinicaltrial.gov identifier: 0011201) Material/Methods: A monocentric study was conducted, applying SBRT by intensified single fraction eight-gray palliative radiotherapy for patients with painful spinal lesions. Patients were stratified by a validated prognostic score (Mizumoto score - REF 1) discriminating 3 level of prognosis (good, intermediate, worse): only patients at worse prognosis (expected inferior to 6 months) were enrolled. SBRT schedule was delivered as simultaneous integrated boost of: 8 Gy to the entire vertebral body + 10-15 Gy to the GTV; boost dose to GTV was allowed in the range of 10 to 15 Gy respecting the Spinal Canal Constraint of 10 Gy maximum dose. Primary endpoint was palliative effect at 1 month, according to International Chow’s criteria (thus, not only according the NRS response). Results: From 2019 to 2023, 31 patients were enrolled, treated on 33 spinal CTVs. All patients were stratified by Mizumoto Score. Dose to entire vertebral body was 8 Gy for all treated lesions; boost dose (in SIB) to the GTV was 15 Gy for 20 CTVs (60,6%), 12 Gy for one CTV (3%) and 10 Gy for 12 CTVs (36,4%). Median follow-up was 2 months (range 1-26 months). At 1 month, three out 31 patients were dead. At 1 month follow-up evaluation (primary endpoint) the distribution of pain response was: complete 45%, partial 52% (i.e.: overall response 97%), indeterminate 3%, progression 0%. No acute/subacute Grade >3 toxicity related to the schedule was reported. Conclusion: Pain response at 1 month according “SAINT” protocol reported rates of overall response 97% (versus conventional response by literature of approximately 60-65%) and complete response 45% (versus conventional 20-25%). This schedule seems effective and will be evaluated in randomized trial versus standard, for patients at worse prognosis, if compliant.