2397 - Simultaneous Integrated Boost vs. Sequential Boost for Postoperative Intensity-Modulated Radiotherapy of Extremity and Trunk Soft Tissue Sarcomas: A Propensity Score Matching-Based Large-Scale Retrospective Analysis
Presenter(s)
S. J. Yang1, Y. Liu1, Y. Song1, H. Fang1, J. Jin2, Y. Tang2, N. Li3, Y. Tang4, S. Qi5, B. Chen6, H. Jing1, Y. Zhai7, W. Zhang3, X. Liu1, S. Chen8, Z. Yang1, Y. Zong1, Y. Wu9, G. Sun4, Y. X. Li10, S. Wang1, and N. N. Lu4; 1Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, 2State Key Laboratory of Molecular Oncology and Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences (CAMS) and Peking Union Medical College (PUMC), Beijing, China, 3State Key Laboratory of Molecular Oncology and Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, 4State Key Laboratory of Molecular Oncology and Department of Radiation Oncology, National Cancer Center/ National Clinical Research Center for Cancer/ Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, 5National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, Beijing, China, 6Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, Beijing, China, 7Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, 8Department of Radiation Oncology, National Cancer Center/ National Clinical Research Center for Cancer/ Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Bejing, China, 9Chinese Academy of Medical Sciences Cancer Institute and Hospital: Cancer Hospital Chinese Academy of Medical Sciences, Beijing, China, 10Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 100021, Beijing, China., Beijing, China, Beijing, China
Purpose/Objective(s): Postoperative radiotherapy with sequential boost for soft tissue sarcoma (STS) typically involves a prolonged treatment course (6-7 weeks). Simultaneous Integrated Boost (SIB) offers convenience; however, evidence in the postoperative setting remains limited. This study aimed to compare the oncologic outcomes and toxicity of SIB-IMRT versus sequential boost.
Materials/Methods: We retrospectively analyzed 289 patients with extremity and trunk STS treated with limb-sparing surgery and adjuvant radiotherapy at a major tertiary cancer center between 2006 and 2024. Patients were classified into the Sequential Boost group (n=173; 60-66 Gy to tumor bed at 2.0 Gy/fraction in 30-33 fractions) and the SIB group (n=116; 60.2 Gy to tumor bed at 2.15 Gy/fraction in 28 fractions, with treatment duration reduced by approximately one week). To minimize selection bias, propensity score matching (PSM) was performed to balance baseline characteristics.
Results: All patients completed treatment as protocol, with no statistically significant differences in the incidence of Grade = 2 late toxicities, including joint stiffness (P>0.9), limb edema (P>0.9), skin toxicity (P=0.3), and fibrosis (P=0.4). In the whole unmatched cohort, there were no signi?cant differences in LRFS, OS, DFS, or DMFS. In the propensity-matched cohort (n=180), the SIB group maintained LRFS and OS comparable to the sequential boost group, while exhibiting a trend toward improved DMFS (P=0.093) and DFS (P=0.3).
Conclusion: Postoperative SIB-IMRT with 2.15 Gy per fraction is an efficient and safe treatment strategy. Compared with the conventional sequential boost, SIB shortens the treatment course without increasing late toxicity, while maintaining comparable oncologic outcomes and might improve efficacy. Future randomized controlled trials are warranted to validate these findings.