Oncologic Outcomes Following Radical Resection With Intraoperative Electron Radiation Therapy In Patients With Recurrent Colorectal Cancer

508 Background: Of the 40,000 rectal cancer patients treated annually, up to 15% will experience a local recurrence (LR). Resection only series for LR report 30–60% positive margin rates. For this reason our institution utilizes intra-operative electron radiation therapy (IOERT) in patients undergoing resection of locally advanced rectal cancer recurrences (LA-RRC). The purpose of this study was to evaluate the oncologic outcomes of patients treated for a LA-RRC with resection and IOERT Methods: Under IRB approval a prospective database of patients with LA-RRC undergoing resection and IOERT from April 2001 to January 2010 was analyzed. Demographic, clinical, and pathologic variables were collected. The Kaplan-Meier method estimated 5-year overall survival (OS) and Fisher's Exact test's explored associations for developing a LR. Results: Fifty patients (32 male, mean age 58 ± 11) underwent resection and IOERT (median dose 1500 cGy, energy 9 MeV). Primary procedures included pelvic exenteration (n = 17), APR (n = 10), LAR (n = 7), isolated pelvic/retroperitoneal tumor (n = 7), para-aortic lymphadenectomy (n = 7), and partial colectomy (n = 2). 56% (n = 28) required multi-visceral resections including partial/total cystectomy (n = 14), small bowel resection (n = 10), vaginectomy (n = 6), hysterectomy (n = 3), oophorectomy (n = 3), nephrectomy (n = 2), and other (n = 4). 34 pelvic sidewall resections and 12 partial sacrectomies were required. Margins were R0 in 37 (74%) and R1 in 13 (26%). Median LOS was 10 days and there were no peri-operative deaths. Five-year OS was 32% with a 19-month follow-up of survivors. 32% (n = 16) developed a pelvic LR, of which 2 were isolated and 14 were in the setting of distant metastasis. No difference was noted in OS (p = 0.5) or LR (p = 0.3) in patients with R0 vs. R1 resections. Initial T (p = 0.1), N (p = 0.2), and stage (p = 0.7) were not found to be associated with LR. Conclusions: This study reveals that resection combined with IOERT provides good local control and reasonable long-term survival in patients with LA-RRC. The similar OS and LR following an R0 and R1 resections could be interpreted as a measure of the beneficial effect of IOERT on microscopic disease. No significant financial relationships to disclose.