Randomized phase II window trial of two schedules of irinotecan with vincristine in patients with first relapse or progression of rhabdomyosarcoma: a report from the Children's Oncology Group.

PURPOSE To compare response rates for two schedules of irinotecan with vincristine in patients with rhabdomyosarcoma at first relapse or disease progression. PATIENTS AND METHODS Patients with first relapse or progression of rhabdomyosarcoma and an unfavorable prognosis were randomly assigned to one of two treatment schedules of irinotecan with vincristine: regimen 1A included irinotecan 20 mg/m(2)/d intravenously for 5 days at weeks 1, 2, 4, and 5 with vincristine 1.5 mg/m(2) administered intravenously on day 1 of weeks 1, 2, 4, and 5; regimen 1B included irinotecan 50 mg/m(2)/d intravenously for 5 days at weeks 1 and 4 with vincristine as in regimen 1A. Disease response was assessed at week 6. Those with responsive disease continued to receive 44 weeks of multiagent chemotherapy that incorporated the assigned irinotecan-vincristine regimen. RESULTS Ninety-two eligible patients were randomly assigned (1A, 45; 1B, 47). Response could be assessed in 89 patients (1A, 42; 1B, 47). There were five complete responses and six partial responses on regimen 1A (response rate, 26%; 95% CI, 16% to 42%) and 17 partial responses on regimen 1B (response rate, 37%; 95% CI, 25% to 51%; P = .36). Neutropenia was less common on regimen 1A (P = .04). One-year failure-free and overall survival rates for regimen 1A were 37% (95% CI, 23% to 51%) and 55% (95% CI, 39% to 69%), respectively, and for 1B, they were 38% (95% CI, 25% to 53%) and 60% (95% CI, 44% to 72%). CONCLUSION There was no difference in the response rates between the two irinotecan-vincristine schedules. We recommend the shorter, more convenient regimen (1B) for further investigation.