Dose-intensive cyclophosphamide with etoposide and vincristine for pediatric solid tumors: a phase I/II pilot study by the Australia and New Zealand Childhood Cancer Study Group.

PURPOSE This pilot study of the Australia and New Zealand Childhood Cancer Study Group investigated the effectiveness and toxicity of a regimen incorporating vincristine (VCR), etoposide, and divided-dose, escalating cyclophosphamide (CPA) (VETOPEC) in 23 patients aged 1 to 20 years with solid tumors. PATIENTS AND METHODS Seventeen patients (group A) had recurrent or refractory tumors after prior multiagent therapy, and six patients (group B) with adverse prognostic indicators were treated at initial presentation. Treatment cycles were 21 to 28 days and consisted of vincristine (0.05 mg/kg) on days 1 and 14, with etoposide (2.5 mg/kg/d) plus escalating CPA on days 1, 2, and 3. The CPA dosage was escalated from 30 mg/kg/d in cycle no. 1 by 5 mg/kg/d in each cycle to a maximum of 55 mg/kg/d in cycle no. 6. RESULTS Of 20 patients assessable for tumor response, 19 (95%) responded after two to six cycles of VETOPEC: seven complete responses (CRs); eight very good partial responses (VGPRs); and four partial responses (PRs). In group A, 13 of 14 (93%) assessable patients responded (five CRs, four VGPRs, four PRs), and in group B, five stage IV and one stage III patient achieved two CRs and four VGPRs. The principal toxicity was myelosuppression. Grade IV neutropenia occurred after 98% of cycles, and the incidence of grade IV thrombocytopenia increased from 37% after cycle no. 1 to 91% after cycle no. 6 (P = .002). A total of 115 cycles delivered were followed by 62 febrile admissions (54%), and showed a significant rise with increasing cycles (P = .001). One patient died of septicemia. CONCLUSION This combination and scheduling produced a high response rate in patients with recurrent, refractory, or advanced solid tumors of childhood. Further studies of this regimen and of strategies to reduce hematologic toxicity are warranted.