A PHASE-I II STUDY OF INTRAOPERATIVE RADIOTHERAPY IN ADVANCED UNRESECTABLE OR RECURRENT CARCINOMA OF THE RECTUM - A RADIATION-THERAPY ONCOLOGY GROUP (RTOG) STUDY/

The Radiation Therapy Oncology Group (RTOG) initiated a phase I/II stu dy of intraoperative radiotherapy (IORT) in advanced or recurrent rect al cancer to assess therapeutic efficacy, toxicity, and establish qual ity control guidelines prior to beginning a phase III trial. From Octo ber 1985 through December 1989, 87 patients with histologically proven adenocarcinoma of the rectum or rectosigmoid with recurrent/persisten t disease after surgery or those primarily inoperable were entered by 14 institutions. Of 86 evaluable patients, 42 patients received IORT e ither alone (n = 15) or in combination with external beam (n = 27). Lo cal control was dependent on the amount of residual disease prior to I ORT, with 2-year actuarial local control of 77% if no gross residual d isease remained vs. 10% with gross residual disease (P = 0.0001). For the recurrent/residual group (n = 33), this observation was also signi ficant with a 2-year actuarial local control rate of 64% if no gross r esidual remained vs. 10% with gross residual disease (P = 0.004). Loca l control translated into an improved survival for all patients and th e recuffent/residual group with 2-year actuarial survival of 88% and 8 9% if no gross residual disease remained vs. 48% and 45% with gross re sidual disease, respectively (P = .0005, 0.006). Six patients (14.6%) experienced four grade 3 and three grade 4 complications as a possible result of IORT during follow-up with a 2-year actuarial risk of major complications of 16%. We conclude that IORT is feasible within a coop erative group and can be performed with acceptable complication rates. A phase III trial to demonstrate a therapeutic advantage for IORT ove r external beam alone is currently in progress.