ESTRO 2025 - Abstract Book

S1679

Clinical - Sarcoma & skin cancer & malignant melanoma

ESTRO 2025

Leiomyosarcoma was the most common histological subtype, representing 65.2% (45) of cases. SBRT was delivered at a median dose of 35 Gy in 5 fractions (range 3-8). Median follow-up duration was 17 months (range 1-90 months). The 1-year and 3-year LC rates were 86% and 73%, respectively (Fig1). Univariate analysis did not identify any significant differences for leiomyosarcoma, delay to oligometastatic disease>24 months, metastatic site (lung vs other) or between patients treated with SBRT and those treated with surgery in terms of local control.

Conclusion: Locally ablative treatments, including surgery and SBRT, demonstrate comparable effectiveness in achieving local control for oligometastatic sarcoma patients. The findings suggest that both modalities can be a valid options. Further prospective studies are warranted to confirm these results.

Keywords: Sarcoma,SBRT,oligometastatic

1960

Digital Poster Analysis of local failures in a Soft Tissue Sarcoma cohort treated with preoperative uhRT Gabriela Studer 1 , Bruno Fuchs 2 , Alexander Mattmann 3 , Tino Streller 3 , Dirk Huebner 1 , David Jeller 1 , Beata Bode 4 , Christoph Glanzmann 1 1 Radiation Oncology, LUKS, Lucerne, Switzerland. 2 Orthopedic Surgery, LUKS, Lucerne, Switzerland. 3 Radiation Oncology, LUKS, LUCERNE, Switzerland. 4 Institute of Pathology, LUKS, Lucerne, Switzerland Purpose/Objective: While normo-fractionation using 50Gy applied in 25 fractions represents the historically most used and best known preoperative RT regimen, ultra-hypofractionated RT (uhRT) with 5 fractions is not (yet) accepted as a 'standard', however bases on a fast increasing literature body derived from clinical data [1]. There are no prospective randomized trials yet comparing normo- vs uhRT. This analysis focused on locally recurred soft tissue sarcoma (STS) patients treated with uhRT. Material/Methods: Between 03.2020-08.2024, 69 consecutive STS patients have been pre-operatively irradiated with 5x 5.0Gy/1w uhRT at our center. Mean/median age of the cohort was 61.8/60y (28-91), gross tumor volume (GTV) measured 452/207cc,