IOeRT in retroperitoneal sarcoma: Towards more organ preservation with comparable oncological outcomes.

BACKGROUND: Retroperitoneal sarcomas (RPS) present a surgical challenge with high rates of local recurrence (LR). We investigated the role of intraoperative electron radiotherapy (IOeRT) in reducing LR after surgical resection of RPS. METHODS: A retrospective analysis of all patients who underwent surgical resection for RPS between 2014 and 2021 at a tertiary academic referral center (n = 172). Patients included underwent surgical resection of their RPS and received IOeRT (n = 36) and were compared by case control matching to patients with similar tumor characteristics (recurrence status and tumor grade) that did not receive IOeRT (n = 36). RESULTS: The median length of hospitalization was 8 days (range, 4-34) in the IOeRT group and 10 days (range, 2-42) in the non-IOeRT group (p = 0.25). The mean operating room (OR) time was 4h (±1.3) and 4h (±1.9) in the IOeRT and non-IOeRT groups respectively, (p = 0.37). Complete resection with R0 margins was achieved in 30 patients (83.3%) and 24 patients (66.6%) in the IOeRT and non-IOeRT groups, respectively (p = 0.1). R1 resection was achieved in 6 patients (16.6%) and 12 patients (33.3%) respectively, (p = 0.1). The resected organ weighted score was significantly different between the groups; score 0 observed in 19 (52.7%) patients in the IOeRT group and 3 (8.3%) in the non-IOeRT group (p < 0.001), score 1 observed in 7 (19.4%) in the IOeRT group and 17 (47.2%) in the non-IOeRT group (p = 0.012). The rate of severe complications (CD score>3) did not differ between the groups, 5 (13.8%) patients in the IOeRT group and 9 (25%) patients in the non-IOeRT group (p = 0.23). No radiation associated complications were noted. The 2-year local recurrence free survival (LRFS) was 75.9% in the IOeRT group and 60.3% in the non-IOeRT group (p = 0.4). The 2-year IOeRT field recurrent free survival (IRFS) was 88.4% in the IOeRT group and 60.3% in the non-IOeRT group (p = 0.04). CONCLUSIONS: The use of IOeRT did not increase the rate of surgical complications and was associated with superior local control in the radiation field, improved organ preservation without an impact on overall survival.