Comparison of Pathologic Tumor Necrosis of Conventional Versus Ultrahypofractionated Preoperative Radiation Therapy in Localized Extremity Soft Tissue Sarcoma and Its Correlation With Clinical Outcomes

Purpose: We aimed to determine if ultrahypofractionated radiation therapy (UHYPO-RT) delivering 6 Gy x 5 fractions yields similar tumor necrosis compared with conventional radiation therapy (CONV-RT) with 2 Gy x 25 fractions in soft tissue sarcoma. The clinical significance of tumor necrosis on loco-regional recurrence-free survival (LRFS), distant disease-free survival (DDFS), and overall survival (OS) were assessed. Methods and Materials: Patients with localized soft tissue sarcoma treated with CONV-RT or UHYPO-RT followed by surgery were included. Good response was defined as tumor necrosis >= 90%, and poor response as <90%. The Mann-Whitney U test compared median tumor necrosis. x2 analysis was used for categorical variables. The Kaplan-Meier function estimated LRFS, DDFS, and OS. Results: A total of 64 patients received CONV-RT, and 45 received UHYPO-RT. The median tumor size was 7.0 cm, with the lower extremity being the most common site (55%). Myxofibrosarcoma (39%) and undifferentiated pleomorphic sarcoma (16%) were the most frequent histologies. The median time from radiation therapy to surgery was 35 days. There was a significant difference in median tumor necrosis between CONV-RT and UHYPO-RT, with rates of 40% and 60%, respectively (P = .022). Patients receiving UHYPORT had a higher percentage of tumor necrosis at the 90% cutoff, achieving 27% compared with 6% for CONV-RT (P = .003). At a median follow-up of 32 months, 12 patients (9%) experienced loco-regional recurrence, 24 patients (19%) faced distant failure, and 19 patients (15%) died of metastatic disease. Patients with <90% necrosis had higher rates of loco-regional (13% vs 0%, P = .207) and distant failure (25% vs 0%, P = .021). Three-year LRFS was 86% for <90% necrosis and 100% for >= 90% necrosis (P = .160). DDFS was 75% for <90% necrosis versus 100% for >= 90% (P = .036). OS rates were 79% and 93%, respectively (P = .290). Conclusions: Preoperative RT with UHYPO-RT was associated with a higher rate of tumor necrosis >= 90% than CONV-RT. Our data suggest that more extensive necrosis is associated with better clinical outcomes. (c) 2024 American Society for Radiation Oncology. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.