Pilot induction regimen incorporating pharmacokinetically guided topotecan for treatment of newly diagnosed high-risk neuroblastoma: a Children's Oncology Group study

Abstract

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 × 10(6) CD34+ cells/kg (range, 1.8 to 541.8 × 10(6) CD34+ 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.

Fig 1.

Study schema. AUC, area under the curve; CisRA, 13 cis-retinoic acid; CrCl, creatinine clearance; GFR, glomerular filtration rate; IV, intravenous; PBSC, peripheral-blood stem cell; PK, pharmacokinetics; XRT, external beam radiation therapy.

Fig 2.

Event-free survival (EFS) and overall survival (OS) for all patients (N = 31). The numbers at risk at the start of years 1 to 5 are given along the curves.