Purpose: The addition of oxaliplatin to fluorouracil in patients with advanced colorectal cancer improves survival. This phase I/II study evaluated the addition of weekly oxaliplatin to preoperative continuous infusion fluorouracil (FU) and external-beam radiation therapy (RT) in patients with locally advanced rectal adenocarcinoma.
Patients and methods: Patients with clinical T3/T4 rectal adenocarcinoma and no evidence of metastases were treated with weekly oxaliplatin, continuous infusion FU 200 mg/m2 intravenously, and RT. A total of 6 weekly doses of oxaliplatin were planned. RT dose was 1.8 Gy/fraction to a total dose of 50.4 Gy. In the phase I portion, oxaliplatin was escalated from 30 to 60 mg/m2.
Results: Forty-four patients were entered onto the study, 18 on the phase I portion and 26 on the phase II portion. The maximum-tolerated dose (MTD) for oxaliplatin was determined to be 60 mg/m2. At the MTD, 12 patients experienced grade 3 or 4 diarrhea, two patients experienced grade 3 neutropenia, and one patient experienced grade 3 thrombocytopenia. Fifty-six percent of patients entered at the MTD completed all 6 weeks of oxaliplatin. Eight (25%) of 32 patients enrolled at the phase II dose experienced a pathologic complete response.
Conclusion: In this multicenter study, the addition of oxaliplatin to intravenous continuous infusion FU and RT for patients with locally advanced rectal cancer was associated with a high pathologic complete response rate but more toxicity than when FU is used alone. A regimen of weekly oxaliplatin, continuous infusion FU, and radiation therapy is now being evaluated by the National Surgical Adjuvant Breast and Bowel Project.