Intraoperative radiotherapy (IORT) as a boost in soft tissue sarcomas of the extremity: long-term results of a retrospective cohort

Abstract Background Intraoperative radiotherapy (IORT) is used as a boost modality for soft tissue sarcoma (STS). It facilitates the precise delivery of a single tumoricidal dose to areas at high risk for residual microscopic disease while minimizing radiation exposure to adjacent radiosensitive structures. This study reports the long-term outcomes of patients with STS of the extremity at high risk of local recurrence treated with high-dose-rate (HDR)-IORT. Methods A cohort of patients with primary STS of the extremities treated between 2013 and 2019 with an intraoperative boost using HDR-IORT as part of their multimodal treatment was retrospectively reviewed. IORT was applied via a flab applicator (flexible silicone-based surface mold) with a dose of 10 Gy prescribed to 0.5 cm depth. Treatment toxicity and recurrence patterns were systematically monitored. Survival was analyzed via the Kaplan‒Meier method. Results Fifty-two patients with a median age of 70 years at diagnosis (range, 22–87) were included. The median tumor size was 10 cm (range, 2–36). Twenty patients (38.5%) had prior unplanned resection, and 14 (26.9%) had resection with close margins (i.e., <1 mm) at oncological excision. External beam radiotherapy (EBRT) was delivered either neoadjuvantly (59.6%) or adjuvantly (38.5%). Eight patients (15.4%) received chemotherapy. At a median follow-up of 80 months (range, 33–128), 21 patients (40.4%) experienced recurrence. Isolated local failure occurred in 2 patients (3.8%), isolated metastatic failure in 16 patients (30.8%), and synchronous local and metastatic failure in 3 patients (5.8%). At five years, the local control and distant control rates were 80.2% and 57.7%, and the progression-free survival and overall survival rates were 51.9% and 58.0%, respectively. Conclusions HDR-IORT boost is a precise and effective technique for dose escalation in primary STS of the extremities, demonstrating favorable local control at long-term follow-up without increasing acute or long-term morbidity in this high-risk patient cohort.