Phase I trial of cetuximab in combination with capecitabine, weekly irinotecan, and radiotherapy as neoadjuvant therapy for rectal cancer

Purpose: To establish the feasibility and efficacy of chemotherapy with capecitabine, weekly irinotecan, cetuximab, and pelvic radiotherapy for patients with locally advanced rectal cancer. Methods and materials: Twenty patients with rectal cancer (clinical Stage uT3-T4 or N+) received a standard dosing regimen of cetuximab (400 mg/m 2 on Day 1 and 250 mg/m 2 on Days 8, 15, 22, and 29) and escalating doses of irinotecan and capecitabine according to phase I methods: dose level I, irinotecan 40 mg/m 2 on Days 1, 8, 15, 22, and 29 and capecitabine 800 mg/m 2 on Days 1–38; dose level II, irinotecan 40 mg/m 2 and capecitabine 1000 mg/m 2; and dose level III, irinotecan 50 mg/m 2 and capecitabine 1000 mg/m 2. Radiotherapy was given to a dose of 50.4 Gy (45 Gy plus 5.4 Gy). Resection was scheduled 4–5 weeks after termination of chemoradiotherapy. Results: On dose level I, no dose-limiting toxicities occurred; however, Grade 3 diarrhea affected 1 of 6 patients on dose level II. Of 5 patients treated at dose level III, 2 exhibited dose-limiting toxicity (diarrhea in 2 and nausea/vomiting in 1). Therefore, dose level II was determined as the recommended dose for future studies. A total of 10 patients were treated on dose level II and received a mean relative dose intensity of 100% of cetuximab, 94% of irinotecan, and 95% of capecitabine. All patients underwent surgery. Five patients had a pathologically complete remission and six had microfoci of residual tumor only. Conclusion: Preoperative chemoradiotherapy with cetuximab, capecitabine, and weekly irinotecan is feasible and well tolerated. The preliminary efficacy is very promising. Larger phase II trials are ongoing.