Intraoperative radiation therapy for the treatment of recurrent retroperitoneal and pelvic tumors: a single-institution analysis.

Background: Patients with recurrent retroperitoneal and pelvic region tumors often require multimodal therapies. Intraoperative radiation therapy (IORT) can deliver high-dose radiation to tumor beds, even if first-line external beam radiation therapy (EBRT) was administered. We evaluated local control (LC) and survival in patients receiving IORT for recurrent tumors.

Methods: We retrospectively analyzed 41 patients with isolated pelvic or retroperitoneal recurrences of colorectal, gynecological, or retroperitoneal primary tumors. Following salvage surgery, all patients underwent tumor bed IORT via electron beam or high dose rate brachytherapy. Isolated IORT (median dose: 15 Gy) was administered to patients who had received first-line EBRT; other patients received IORT (median dose 12 Gy) plus EBRT. Local (LF), regional (RF), and distant failures (DF) were evaluated, and the Kaplan-Meier method and log-rank test were used to evaluate and compare overall survival (OS) from the date of IORT.

Results: Forty-one patients underwent 44 treatments, including 27 (61.3%) isolated IORT and 17 (38.7%) IORT and EBRT combination regimens. The median follow-up was 8.1 years (range: 4.4-11.7 years), and the 2, 5, and 8 year overall LC rates were 87.9, 64.0, and 49.8%, respectively. Regarding resection status, the respective 2, 5, and 8 year LC rates were 90, 76, and 76% for R0 resection and 75, 25, and 0% for R1 resection (p < 0.001). The 2, 5, and 8 year OS rates were 68, 43, and 26%, respectively. OS was better among patients with LC (p < 0.001). Twenty-four patients (58.5%) experienced a DF, and the 5 year OS rates for the patients with and without DF were 36 and 52%, respectively (p = 0.04). In a multivariate analysis, LF (p = 0,012) and recurrent retroperitoneal sarcoma (p = 0,014) were identified as significant predictors of worse OS. Thirteen patients (31%) developed clinically treatable complications related to IORT.

Conclusions: Many patients achieve long-term OS and LC without significant morbidity after salvage surgery and IORT, especially in case of clear margins.