Selection criteria for treatment of rectal cancer with combined external and endocavitary radiation

PURPOSE: The aim of this study was to identify factors predictive of recurrence of rectal tumors treated with combined external and endocavitary radiation. METHODS: Seventy-two patients with rectal cancer were evaluated clinically and with transrectal ultrasound before combined external and endocavitary radiation. Ideal lesions were moderately differentiated, mobile, not ulcerated, <3 cm in diameter, and <12 cm from the anal verge. External radiation (4,500 cGy) was given during five weeks followed by endocavitary radiation (3,000 cGp x 2). Median followup was 31 (range, 7-93) months. RESULTS: Pretreatment transrectal ultrasound stages were uT1 (6 patients), uT2(27 patients), and uT3 (39 patients). Clinical evaluation identified 26 ideal and 46 nonideal tumors. Overall recurrence was 36 percent; mean time to recurrence was 12 months. Ideal lesions recurred less than nonideal (15 vs. 48 percent; P = 0.01). Mobile lesions recurred less than tethered lesions (26 vs. 52 percent; P = 0.048). Transrectal ultrasound stage was predictive of recurrence (0 percent uT1, 22 percent uT2, and 51 percent uT3; P = 0.015). Surgery was possible in 14 of 17 patients with pelvic recurrence only; 11 patients (65 percent) had curative surgery. Distant metastases occurred in nine patients; all had pelvic recurrences, and six died of disease. CONCLUSION: Patients with uT3 or nonideal rectal cancers should not be offered combined external and endocavitary radiation for cure. Transrectal ultrasound stage is the only independent predictor of recurrence.