ADJUVANT CONTINUOUS-INFUSION 5-FU, WHOLE-ABDOMINAL RADIATION, AND TUMOR BED BOOST IN HIGH-RISK STAGE-III COLON-CARCINOMA - A SOUTHWEST-ONCOLOGY-GROUP PILOT-STUDY

Purpose: Results of a combined modality adjuvant pilot program of low- dose continuous-infusion 5-fluorouracil, whole-abdominal radiation, an d tumor bed boost in patients with colon cancer with involved nodes an d serosal involvement are presented. Methods and Materials: Forty-one eligible patients with completely resected T3N1-2M0 colon cancer (modi fied Astler-Coller C2) were treated with 5-fluorouracil (5-FU) at a do se of 200 mg/m(2)/day by continuous infusion and 30 Gy of concomitant whole-abdominal radiation in 1 Gy fractions. An additional 16 Gy boost to the tumor bed was administered in 1.6 Gy fractions. After completi on of combined modality treatment and a 21-day rest period, patients r eceived 4 days of 5-FU at a dose of 1000 mg/m(2) by continuous infusio n every 28 days for nine cycles. Results: Five-year disease-free and o verall survival estimates were 58 and 67%, respectively, for all T3N1- 2 patients. Five-year disease-free and overall survival estimates for the 19 patients with four or fewer nodes were both 61%. Five-year dise ase-free survival and overall survival estimates for the 20 patients w ith more than four involved nodes were 55% and 74%, respectively (the exact number of involved nodes were unknown for two patients). Disease -free and overall survival estimates for patients treated with 5-FU an d radiation compare favorably to the 5-FU plus levamisole arm of the i ntergroup adjuvant colon study (Int 0035/SWOG 8591) in patients with m ore than four positive nodes where the 5-year disease-free and overall survival estimates were 35% and 39%, respectively. Disease-free and o verall survival estimates for patients with four or fewer nodes in the 5-FU plus levamisole arm of the intergroup study were 64 and 68%, whi ch is not markedly different from results obtained with radiation and 5-FU in the current study. There were no treatment-related fatalities. Seventeen percent of patients had severe and 7% had life-threatening toxicity of any kind. One patient had an acute partial bowel obstructi on and two patients had chronic low grade enteritis. Conclusion: Conti nuous infusion 5-FU and whole-abdominal radiation with tumor bed boost should be further investigated in a larger trial of T3N1-2 colon canc er.