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

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 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.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.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.