ESTRO 2025 - Abstract Book

S1664

Clinical - Sarcoma & skin cancer & malignant melanoma

ESTRO 2025

899

Digital Poster Prognostic Factors in Extremity Soft Tissue Sarcomas Treated with Radiotherapy. Arthur LEBAS 1 , Clara LE FEVRE 1 , Waisse WAISSY 2 , David BRINKERT 3 , NOEL Georges 1

1 Radiotherapy Department, Institut de Cancérologie Strasbourg Europe (ICANS), Strasbourg, France. 2 Radiotherapy Department, Léon Bérard Center, Lyon, France. 3 Orthopedic Surgery Department, University Hospital of Strasbourg, Strasbourg, France Introduction: Prognostic factors for extremity soft tissue sarcomas (ESTS) treated with multimodal therapy, including surgery and radiotherapy (RT), remain a subject of debate across various heterogeneous studies. Methods: We retrospectively analyzed non-metastatic ESTS patients treated with RT between 2007 and 2020 in Strasbourg, France. We evaluated local control (LC), distant control (DC), overall survival (OS), and complications associated with multimodal treatment. Results: A total of 169 patients diagnosed with localized extremity soft tissue sarcomas were included, with a median age of 64 years (range 21-94). ESTS were primarily located proximally (74.6%) and in the lower limbs (71.0%). Most tumors were grade 2-3 (71.1%), deep (86.4%), and with clear R0 margins (63.9%). Helical tomotherapy was the most commonly used radiotherapy technique (79.3%). The median prescribed biological equivalent dose (BED) was 75 BEDGy4 (45.0–109.9). The median follow-up period was 5.5 years. The 5- and 10-year LC, DC, and OS rates were 91.7%, 76.8%, 83.8%, and 84.2%, 74.1%, and 77.6%, respectively. In univariate analysis, LC was significantly worse for patients who received a dose below 75 BEDGy4 (p=0.015). Deep tumors were associated with shorter survival (p<0.05), and grade 2-3 tumors as well as undifferentiated pleomorphic sarcomas (UPS) were linked to both shorter DC and OS (p<0.05). IMRT was associated with better LC than 3D-CRT (p=0.018). Multivariate analysis identified liposarcoma as having better OS (p<0.05) and distant relapses with lower survival (p<0.0001). Wound complications occurred in 22.6% of patients, with proximal and lower limb tumors as significant risk factors. Acute RT-related complications included radiodermatitis, with grade ≥2 occurring in 43.1% of patients, associated with superficial tumors. Grade ≥2 edema was present in 1.8% of cases. Chronic complications included telangiectasia (21.7%) and fibrosis (38.7%), with higher rates associated with larger PTVs and higher doses, respectively. Fractures occurred in five patients, mostly in the femur (40%). Conclusion: In ESTS patients, RT combined with surgery is well-tolerated with manageable side effects and is associated with excellent long-term LC, DC, and OS rates. IMRT demonstrated better LC compared to 3D-CRT. Liposarcoma was a favorable prognostic factor for OS. Intermediate- and high-grade tumors, as well as deep tumors, were associated with lower DC and OS.

Keywords: Radiotherapy, soft tissue sarcoma, complications