Purpose: A Phase I study was conducted to determine the maximal tolerated dose and the dose-limiting toxicity (DLT) of oxaliplatin (OXA) combined with capecitabine and radiotherapy as adjuvant treatment in patients with operable rectal cancer.
Patients and methods: A total of 21 patients with Stage II or III rectal adenocarcinoma after curative surgery were treated with radiotherapy to a total dose of 50 Gy in 5 weeks. OXA was administered at a dosage of 40 (n = 6), 50 (n = 3),60 (n = 3), 70 (n = 3), or 80 mg/m(2) (n = 6) once a week for 2 weeks (first cycle) followed by a second cycle after a 7-day break. Capecitabine at a fixed dose of 1,300 mg/m(2)/d was administered orally at the same schedule as for OXA. DLT was defined as Grade 3 or 4 hematologic and nonhematologic toxicity.
Results: Grade 1-3 leukopenia, diarrhea, and nausea/vomiting were the most common toxic side effects, and most were Grade 1-2. A DLT was first observed in 1 of 3 patients at 40 mg/m(2) (Grade 3 diarrhea) but was not observed in the next 3 patients at the same level or in patients who received a dose level of 50-70 mg/m(2). At 80 mg/m(2), DLT occurred in 3 of 6 patients (1 Grade 4 leukopenia and 2 Grade 3 diarrhea).
Conclusions: OXA combined with a fixed dose of capecitabine at 625 mg/m(2) twice daily by mouth plus radiotherapy in the adjuvant setting was tolerable and clinically feasible. The maximal tolerated dose of OXA in this setting was 80 mg/m(2), comparable to the maximal tolerated dose of OXA in the neoadjuvant setting.