Locally advanced rectal carcinoma: pelvic control and morbidity following preoperative radiation therapy, resection, and intraoperative radiation therapy.

PURPOSE

To determine the impact of intraoperative radiation therapy (IORT) combined with preoperative external beam irradiation and surgical resection in patients with locally advanced, unresectable rectal carcinoma.

METHODS AND MATERIALS

Between 1982 and 1993, 40 patients with locally advanced colorectal cancer unresectable at initial presentation were treated with preoperative external beam radiation therapy (median dose 50.4 Gy). Thirty patients received concurrent 5-fluorouracil. Twenty-seven patients had primary tumors and 13 had recurrent disease; 1 patient had a solitary hepatic metastasis at the time of surgery. Four to 6 weeks after radiation, surgical resection was undertaken, and if microscopic or gross residual disease was encountered, IORT was delivered to the tumor bed. Patients with an unevaluable or high-risk margin were also considered for IORT. IORT was delivered through a dedicated 300-kVp orthovoltage unit. The median dose of IORT was 12.5 Gy (range 8-20). The dose was typically prescribed to a depth of 1-2 cm. The median follow-up was 33 months (range 5-100).

RESULTS

Thirty-three patients were able to undergo a curative resection (83%). Five patients had gross residual disease despite aggressive surgery. Seven patients did not receive IORT: six because of clear margins, and one with gross disease that could not be treated for technical reasons. The remainder of the patients (26) received IORT to the site of pelvic adherence. The crude local control rates for patients following complete resection with negative margins were 92% for patients treated with IORT and 33% for patients without IORT. IORT was ineffective for gross residual disease. Pelvic control was none of four in this setting. The crude local control rate of patients with primary cancer was 73% (16 of 22), as opposed to 27% (3 of 11) for these with recurrent cancer. The 5-year actuarial overall survival and local control rates for patients undergoing gross complete resection and IORT were 64% and 75%, respectively. Seventeen of the 26 patients (65%) who received IORT experienced pelvic complications, as opposed to two patients (28%) who did not receive IORT. The incidence of complications was similar in the patients with primary versus recurrent disease. All cases were successfully treated with the placement of a posterior thigh myocutaneous flap. Of note, no pelvic osteoradionecrosis was seen in this series.

CONCLUSION

Patients with locally advanced carcinoma of the rectum were aggressively treated with combined modality therapy consisting of preoperative external beam radiotherapy, surgery, and IORT. The pelvic control rate was 82% for patients with minimal residual disease. IORT failed to control gross residual disease. The incidence of pelvic wound healing problems was 65% in this series; however, a reconstructive procedure which replaced irradiated tissue with a vascularized myocutaneous flap was successful in treating this complication. We believe that IORT has therapeutic merit in the treatment of locally advanced rectal cancer, particularly in the setting of minimal residual disease.