Simultaneous integrated boost versus sequential boost for postoperative intensity-modulated radiotherapy of extremity and trunk soft tissue sarcomas: a propensity score matching-based large-scale retrospective analysis

Postoperative radiotherapy with sequential boost for soft tissue sarcoma (STS) typically requires 6–7 weeks. Simultaneous Integrated Boost (SIB) can shorten the treatment course, but evidence in the postoperative setting remains limited. This study aimed to compare the oncologic outcomes and toxicity between postoperative SIB and sequential boost radiotherapy. We retrospectively analyzed 275 patients who underwent surgery and postoperative radiotherapy at a major tertiary cancer center between 2006 and 2024. The Sequential Boost group included 166 patients who received a tumor-bed dose of 60–66 Gy in 30–33 fractions. The SIB group included 109 patients who generally received 60.2 Gy 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. In the unmatched cohort, unadjusted analyses nominally favored SIB for DFS and DMFS ( P = 0.046 and P = 0.048, respectively), whereas LRFS and OS did not differ significantly between groups. After multivariable adjustment, boost technique was not significantly associated with any survival endpoint. PSM yielded 96 matched pairs, with no statistically significant between-group differences in DFS, DMFS, LRFS, or OS. The distributions of maximum toxicity grades recorded during follow-up did not differ significantly between groups for joint dysfunction, edema, skin toxicity, or subcutaneous fibrosis. Postoperative SIB enables delivery of radiotherapy within a 28-fraction treatment course. After adjustment for measured baseline differences, SIB was not associated with significantly worse oncologic outcomes or increased recorded toxicity compared with sequential boost. These findings support SIB as a potentially practical treatment approach that needs prospective validation. Not applicable.