Vinorelbine and low-dose cyclophosphamide in the treatment of pediatric sarcomas: pilot study for the upcoming European Rhabdomyosarcoma Protocol.

BACKGROUND: Following their previous report on the activity of vinorelbine in the treatment of rhabdomyosarcoma, the authors report the results of a pilot study aimed at defining the optimal dose of vinorelbine when this agent is used in conjunction with continuous, orally administered low-dose cyclophosphamide to treat patients with refractory or recurrent sarcoma. It is hoped that the combination of vinorelbine and low-dose cyclophosphamide can be used as a maintenance regimen in an upcoming European trial involving high-risk patients with rhabdomyosarcoma. METHODS: In the current pilot study, the cyclophosphamide dose was fixed at 25 mg/m2 per day for 28 days. Vinorelbine was administered intravenously on Days 1, 8, and 15, with trial doses escalated from an initial level of 15 mg/m2 in steps of 5 mg/m2; intrapatient dose escalation was not allowed. RESULTS: Between April 2002 and November 2003, 18 patients ages 2-23 years were treated with the study regimen after having received 1-4 (median, 2) other regimens previously. Ninety cycles were administered in total (median, 5 cycles per patient; range, 1-10 cycles per patient). Two cases of dose-limiting toxicity (Grade 4 neutropenia in both cases) were observed among the 5 patients who received vinorelbine at a dose of 30 mg/m2. Of the 41 cycles in which vinorelbine was administered at a dose of 25 mg/m2, Grade > or = 3 neutropenia was observed in 15 (37%); no other major toxicity was documented in association with these cycles. One complete remission and 6 partial remissions were noted among the 17 patients who had measurable disease. Three of the eight assessable patients with rhabdomyosarcoma (which was embryonal in two cases and alveolar in one) had responses to treatment. CONCLUSIONS: Combination therapy involving vinorelbine and low-dose cyclophosphamide was found to be feasible and to possess activity against recurrent sarcomas. The maintenance therapy doses recommended for use in the upcoming European trial are cyclophosphamide 25 mg/m2 per day for 28 days and vinorelbine 25 mg/m2 on Days 1, 8, and 15.