Phase III Comparison of Two Irinotecan Dosing Regimens in Second-line Therapy of Metastatic Colorectal Cancer

Purpose: Randomized trials in fluorouracil (FU)-refractory colorectal cancer demonstrate significant survival advantages for patients receiving irinotecan. We prospectively compared the efficacy and tolerability of two irinotecan regimens (once a week for 4 weeks followed by a 2-week rest period [weekly] v once every 3 weeks) in such patients.

Patients And Methods: This multicenter, open-label, phase III study randomly assigned patients in a 1:2 ratio to irinotecan given either weekly (125 mg/m(2)) or once every 3 weeks (350 mg/m(2), or 300 mg/m(2) in patients who were >/= 70 years of age, who had Eastern Cooperative Oncology Group performance status equal to 2, or who had prior pelvic irradiation).

Results: With median follow-up of 15.8 months, there was no significant difference in 1-year survival (46% v 41%, respectively; P =.42), median survival (9.9 v 9.9 months, respectively; P =.43), or median time to progression (4.0 v 3.0 months, respectively; P =.54) between the two regimens. Grade 3/4 diarrhea occurred in 36% of patients treated weekly and in 19% of those treated once every 3 weeks (P =.002). Grade 3/4 neutropenia occurred in 29% of patients treated weekly and 34% of those treated once every 3 weeks (P =.35). Treatment-related mortality occurred in five patients (5.3%) receiving irinotecan weekly and three patients (1.6%) given therapy once every 3 weeks (P =.12). Global quality of life was not statistically different between treatment groups.

Conclusion: Irinotecan schedules of weekly and of once every 3 weeks demonstrated similar efficacy and quality of life in patients with FU-refractory, metastatic colorectal cancer. The regimen of once every 3 weeks was associated with a significantly lower incidence of severe diarrhea.