Purpose: To assess the outcome of aggressive multimodality treatment with preoperative external beam radiation therapy (EBRT), extended circumferential margin excision (ECME) and intraoperative electron beam radiation therapy (IOERT) in patients with locally advanced primary rectal cancer.
Methods and materials: Thirty-eight patients with primary locally advanced rectal cancer, but without distant metastases, received multimodality treatment. CT-scan showed extension to other structures in 15 patients (39%) and definite infiltration into the surrounding structures in 23 patients (61%). All patients received preoperative EBRT (dose range 25-61 Gy) and 82% received 50.4 Gy. The resection types were: 12 low anterior resections (31%), 14 abdomino-perineal resections (37%), 6 abdomino-transsacral resections (16%), and 6 pelvic exenterations (16%). The IOERT dose ranged from 10 to 17.5 Gy depending on the completeness of the resection.
Results: There was no perioperative mortality. The resection margins were microscopically negative in 31 patients (82%), microscopically positive in 4 (10%), and positive with gross residual disease in 3 patients (8%). Pelvic recurrences were observed in 5 patients (13%) including 3 IOERT infield failures. The overall 3-year local control, disease-free survival (DFS), and survival rates were 82%, 65%, and 72%, respectively. Negative resection margins were the most significant prognostic factor with regard to DFS (p = 0.0003) and distant control (p = 0.002) compared with cancer involved surgical margins.
Conclusion: A high percentage of curative resections can be achieved in this group of patients with locally advanced rectal cancers. Adding IOERT to preoperative EBRT and ECME achieves high local control rates and possibly improves survival.