ESTRO 2025 - Abstract Book

S1728

Clinical - Sarcoma & skin cancer & malignant melanoma

ESTRO 2025

4358

Digital Poster Preoperative Hypofractionation for Soft Tissue Sarcoma: Outcome, Pathological Response and Acute Toxicity Laura P Guzmán-Gómez, Marta Pérez Cobos, Ignacio Navarro, María Sánchez Pérez, Gladys Almeida Pachas, Magnolia Rincón Pérez, Sylvia Gómez-Tejedor, Erika Marquez Clemente, Javier Luna Tirado, Ignacio Azinovic Radiation Oncology, Fundacion Jimenez Diaz University Hospital, Madrid, Spain Purpose/Objective: Preoperative radiotherapy (RT) combined with surgery is the cornerstone of treatment for localized soft tissue sarcoma (STS). Emerging evidence indicates that preoperative hypofractionation does not increase toxicity rates or compromise oncological outcomes compared to normofractionated RT. This study reports our institutional experience, aiming to assess the impact of hypofractionation on pathological response, acute toxicity and local control (LC). Material/Methods: From August 2021 to January 2024, 19 patients with limb or trunk STS underwent hypofractionated preoperative RT (HFRT) in two treatment schemes: 30 Gy in 5 fractions (ultra hypofractionated RT - UHFRT) and 42,75Gy in 15 fractions (moderate hypofractionated RT - MHFRT). A favorable pathologic response (fPR) was considered as ≥ 80% of necrosis and/or percentage of viable tumor <25% on specimen examination. Results: All patients completed RT treatment with no interruptions. Thirteen patients (68,4%) received MHFRT. The median tumor size was 12,4cm and mean time between end of RT and surgery was 4.5 weeks. Fifteen patients (78,9%) achieved a fPR. No patient experienced ≥ grade 3 acute skin toxicity during RT or within 4 weeks post-treatment. Grade 1-2 acute skin toxicity was observed in 12 patients (63,2%). Acute major wound complications (including secondary intervention for wound repair and prolonged wound care) occurred in 5 patients (26,3%). With a median follow-up of 18 months (9-26 months), the 1- and 2-year LC rates were 100%. Conclusion: Preoperative HFRT for STS is well-tolerated and shows promising pathological response rates and local control outcomes comparable to conventional fractionation. However, no randomized Phase III trials comparing normofractionated RT and HFRT in STS have been published to date. Additionally, longer follow-up is necessary to assess late toxicities and functional outcomes. References: 1. Guadagnolo, B Ashleigh et al. Hypofractionated, 3-week, preoperative radiotherapy for patients with soft tissue sarcomas (HYPORT-STS): a single-centre, open-label, single-arm, phase 2 trial. The Lancet Oncology,1547-1557, 2022. 2. M Bedi, R Singh et al. Is 5 the New 25? Long-Term Oncologic Outcomes From a Phase II, Prospective, 5-Fraction Preoperative Radiation Therapy Trial in Patients With Localized Soft Tissue Sarcoma. Advances in Radiation Oncology, 2022. 3. Montero, A., Chen-Zhao, X., Ciérvide, R. et al. Moderate hypofractionated radiation therapy and pathologic response for soft tissue sarcomas (STS) of limbs and trunk: experience from a tertiary cancer center. Clin Transl Oncol 26, 204–213, 2024 Keywords: Hypofractionation, Soft Tissue sarcoma