Intraoperative Radiation After Pelvic Short Course Radiation-Based Total Neoadjuvant Therapy for Patients With Rectal Adenocarcinoma at High Risk for Local Recurrence

Background: Short course radiation-based total neoadjuvant therapy can improve disease-free survival for patients with high-risk locally advanced rectal cancer. Tumors that involve or threaten the circumferential resection margin have a particularly high risk of local recurrence. Intraoperative radiation therapy enables treatment escalation at the threatened or involved margin at the time of surgery. Patients and Methods: Patients with rectal adenocarcinoma treated with preoperative short course radiotherapy-based total neoadjuvant therapy and intraoperative radiation at the time of surgery were identified. All patients had a threatened or involved circumferential resection margin on magnetic resonance imaging at the time of diagnosis. Treatment details, radiation toxicities, postoperative complications and oncologic outcomes were recorded. Results: Ten patients received intraoperative radiation after short course radiation-based total neoadjuvant therapy. All patients had an involved or threatened circumferential resection margin, 60% had extramural venous invasion, and 60% had positive lateral pelvic lymph nodes. Seven patients had negative surgical margins (≥ 2 mm), and 3 patients had an R1 resection with radial margins < 2 mm. The median [IQR] length of hospitalization after surgery was 11 [7-14] days. Three patients required readmission and 2 patients required reoperation due to complications including anastamotic leak and abscess. With a median follow up of 19.5 months postoperatively, no patient developed a pelvic recurrence, and 6 patients developed distant recurrences. Conclusions: The use of intraoperative radiation after a short course radiotherapy-based neoadjuvant therapy is safe and feasible. Further data are needed to determine whether the addition of intraoperative radiation improves local recurrence rates over preoperative radiation alone.