CHEMOTHERAPY: Patients with intermediate-risk or high-risk neuroblastoma receive chemotherapy (including cyclophosphamide) according to the standard of care for the stage of primary neuroblastoma, beginning on day 0. Patients with low-risk neuroblastoma (and not receiving other chemotherapy) receive cyclophosphamide IV over 1 hour on day 0. Treatment repeats every 4 weeks for 6 courses in the absence of disease progression or unacceptable toxicity. All patients receive oral prednisone twice daily for 3 months and then every other day for 7-15 months.