ESTRO 2025 - Abstract Book

S1464

Clinical – Mixed sites & palliation

ESTRO 2025

Material/Methods: In the Destroy-1 trial [1], two arms (d) and (e) were designed for retreatment of recurrence after prior in-field radiotherapy (RT). Arm (d) included patients with recurrences pre-irradiated with doses over 60 Gy or in areas previously irradiated in the small intestine, while arm (e) focused on recurrences in sites that received less than 60 Gy. The total dose was escalated to 45 Gy for arm (d) and 50 Gy for arm (e) across six levels. Each cohort, consisting of six patients, was assessed for dose-limiting toxicity (DLT), defined as any radiation-related toxicity > Grade 3 within six months of SBRT. The maximum tolerated dose (MTD) was identified as the highest dose level that caused DLT in two or more participants, or the final dose cohort. Late adverse events occurring beyond six months post SBRT were documented as late toxicities but were excluded from the DLT evaluation. Results: A total of 121 lesions from 97 consecutive patients (M/F:55/42; median age: 69 years; range: 44-98) were treated between September 2004 and August 2023. The most common retreatment sites were the pelvis (40.5%) and thorax (31.4%), with nodal recurrences comprising 57% of the lesions. Acute toxicity was recorded in 20 cases for arm (d) and 6 for arm (e), all low grade (G1-G2), primarily gastrointestinal, except for one G4 soft tissue toxicity in arm (d). Regarding late toxicity, arm (d) had a median follow-up of 18 months (range: 6 – 133 months) with only 5 low-grade events (< G2). Arm (e), with a median follow-up of 17 months (range: 6 – 143 months), recorded 7 late events, including one occurrence of Grade 4 skin toxicity in the dorsal area. The overall clinical response across all 121 lesions showed 65 (53.7%) complete responses, 35 (28.9%) partial responses, and 19 (15.7%) stable diseases, yielding an overall disease control rate of 98.3%. Progression occurred in 2 cases (1.7%). One-year local control was 87.6%, with 84.7% for arm (d) and 92.0% for arm (e). One-year Distant Metastases Free-Survival, Disease Free Survival, and Overall Survival were 54.5%, 46.7%, and 78.1%, respectively. Conclusion: MTD was not exceeded: the 45 Gy dose in the "d" arm, and the 50 Gy dose in the "e" arm, were administered with an acceptable toxicity profile.

Keywords: SBRT; Reirradiation; Dose Escalation

References: 1.Deodato F, Macchia G, Cilla S, Ianiro A, Sallustio G, Cammelli S, Buwenge M, Mattiucci GC, Valentini V, Morganti AG. Dose escalation in extracranial stereotactic ablative radiotherapy (DESTROY-1): A multiarm Phase I trial. Br J Radiol. 2019 Feb;92(1094):20180422. doi: 10.1259/bjr.20180422. Epub 2018 Nov 1. PMID: 30325662; PMCID: PMC6404833.

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Digital Poster SBRT local control and toxicity: our experience in a tertiary care hospital María C. Matienzo Barreto, José Javier Martín Ortega, María Elena García Morales, Lidia Gómez Perea, Claudio Fuentes Sánchez Radiation oncology, Hospital Universitario Nuestra Señora de la Candelaria, Santa Cruz de Tenerife, Spain Purpose/Objective: Stereotactic body radiotherapy (SBRT) is a flourishing treatment. It has demonstrated benefit in certain patients including oligometastatic patients. The aim of this study is to evaluate local control (LC) and toxicity in bone, lymph node and visceral metastases in patients treated with SBRT.

Material/Methods: Retrospective observational study. From August 2016 to November 2023.