Pilot Induction Regimen Incorporating Pharmacokinetically Guided Topotecan for Treatment of Newly Diagnosed High-Risk Neuroblastoma: A Children's Oncology Group Study

Purpose To assess the feasibility of adding dose-intensive topotecan and cyclophosphamide to induction therapy for newly diagnosed high-risk neuroblastoma (HRNB). Patients and Methods Enrolled patients received two cycles of topotecan (approximately 1.2 mg/m(2)/d) and cyclophosphamide (400 mg/m(2)/d) for 5 days followed by four cycles of multiagent chemotherapy (Memorial Sloan-Kettering Cancer Center [MSKCC] regimen). Pharmacokinetically guided topotecan dosing (target systemic exposure with area under the curve of 50 to 70 ng/mL/hr) was performed. Peripheral-blood stem cell (PBSC) harvest and surgical resection of residual primary tumor occurred after cycles 2 and 5, respectively. Patients achieving at least a partial response received myeloablative chemotherapy with PBSC rescue and radiation to the presurgical primary tumor volume. Oral 13-cis-retinoic acid maintenance therapy was administered twice daily for 14 days in six 28-day cycles. Results Thirty-one patients were enrolled onto the study. No deaths related to toxicity or dose-limiting toxicities occurred during induction. Mucositis rarely occurred after topotecan cycles (9.7%) in contrast to 30% after MSKCC cycles. Thirty patients underwent PBSC collection with median 31.1 x 106 CD34 + cells/kg (range, 1.8 to 541.8 x 106 CD34 x cells/kg), all negative for tumor contamination by immunocytochemical analysis. Targeted topotecan systemic exposure was achieved in 26 (84%) of 31 patients. At the end of induction, 26 patients (84%) had tumor response and one patient had progressive disease. In the overall cohort, 3-year event-free and overall survival were 37.8% +/- 9.4% and 57.1% +/- 9.4%, respectively. Conclusion This pilot induction regimen was well tolerated with expected and reversible toxicities. These data support investigation of efficacy in a phase III clinical trial for newly diagnosed HRNB.