Radiation therapy oncology group 0247: A randomized phase II study of neoadjuvant capecitabine and irinotecan or capecitabine and oxaliplatin with concurrent radiotherapy for patients with locally advanced rectal cancer

Purpose: To evaluate the rate of pathologic complete response (pCR) and the toxicity of two neoadjuvant chemoradiotherapy (chemoRT) regimens for Stage T3-T4 rectal cancer in a randomized Phase II study. Methods and Materials: Patients with Stage T3 or T4 rectal cancer of <12 cm from the anal verge were randomized to preoperative RT (50.4 Gy in 1.8-Gy fractions) with concurrent capecitabine (1,200 mg/m ²/d Mondays through Friday) and irinotecan (50 mg/m ² weekly in four doses) (Arm 1) or concurrent capecitabine (1,650 mg/m ²/d Monday through Friday) and oxaliplatin (50 mg/m ² weekly in five doses) (Arm 2). Surgery was performed 4-8 weeks after chemoRT, and adjuvant chemotherapy 4-6 weeks after surgery. The primary endpoint was the pCR rate, requiring 48 evaluable patients per arm. Results: A total of 146 patients were enrolled. The protocol chemotherapy was modified because of excessive gastrointestinal toxicity after treatment of 35 patients; 96 were assessed for the primary endpoint - the final regimen described above. The patient characteristics were similar for both arms. After chemoRT, the rate of tumor downstaging was 52% and 60% and the rate of nodal downstaging (excluding N0 patients) was 46% and 40%, for Arms 1 and 2, respectively. The pCR rate for Arm 1 was 10% and for Arm 2 was 21%. For Arm 1 and 2, the preoperative chemoRT rate of Grade 3-4 hematologic toxicity was 9% and 4% and the rate of Grade 3-4 nonhematologic toxicity was 26% and 27%, respectively. Conclusions: Preoperative chemoRT with capecitabine plus oxaliplatin for distal rectal cancer has significant clinical activity (10 of 48 pCRs) and acceptable toxicity. This regimen is currently being evaluated in a Phase III randomized trial (National Surgical Adjuvant Breast and Bowel Project R04).