Dose-intensive use of cyclophosphamide in ablation of neuroblastoma

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Abstract
A dose-intensive, cyclophosphamide (CPM)-based chemotherapy regimen was tested in 22 children with newly diagnosed metastatic or refractory neuroblastoma. The N5 protocol consisted of four courses of CPM (140 mg/kg over 2 days), doxorubicin (45 mg/m2 over 3 days), and vincristine (0.05 mg/kg/d on days 1, 2, and 9) (CAV regimen), followed by three courses of cisplatin (40 mg/m2/d) and VP16 (150 mg/m2/d) for 3 days (PVP regimen). Courses started when the neutrophil count was 500/μl or greater and the platelet count was greater than 100,000/μl; most courses began by day 21. Extramedullary toxicities were mild. All patients had Grade 3 to 4 myelosuppression, yet bone marrow harvested after the N5 protocol engrafted in 11 of 11 patients whose post-N5 treatments required autologous bone marrow transplantation (ABMT). Among 14 previously untreated patients, the N5 plus surgery achieved 9 complete remissions (CR) or very good partial remissions (VGPR) and 3 partial remissions (PR). An additional patient achieved CR with CAV, but experienced a recurrence in the bone marrow after PVP. The sole previously untreated patient whose bone marrow disease did not resolve received courses of the N5 at prolonged intervals (for nonmedical reasons). Among eight patients with progressive (six patients) or refractory (two patients) disease while on other, lower dose regimens, the N5 plus surgery achieved five CR/VGPR, two PR, and one minor response (MR). In conclusion, dose-intensive use of CPM has tolerable toxicity and does not preclude autografting; when administered in conjunction with other cytotoxic agents, it is highly effective against metastatic neuroblastoma and causes regressions of disease resistant to less intensive regimens. This approach plus surgery reliably achieves a minimal disease state that may be amenable to definitive ablation with relatively nontoxic therapies.