Treatment of High-Risk Neuroblastoma
Assessment of risk for low-stage MYCN-amplified neuroblastoma is controversial because it is so rare. A study of 87 INSS stage 1 and 2 patients pooled from several clinical trial groups demonstrated no effect of age, stage, or initial treatment on outcome. The EFS and OS were 53% and 72%, respectively. Survival was superior in patients whose tumors were hyperdiploid rather than diploid (EFS 82% ± 20% vs. 37% ± 21%; OS 94% ± 11% vs. 54% ± 15%). The overall EFS and OS for infants with stage 4 and 4S disease and MYCN-amplification was only 30% at 2 to 5 years post-treatment in a European study.
Standard Treatment Options
Patients classified as high risk receive treatment with an aggressive regimen of combination chemotherapy consisting of very high drug doses, generally termed induction. Drugs often used include cyclophosphamide, ifosfamide, cisplatin, carboplatin, vincristine, doxorubicin, etoposide, and topotecan. COG has completed a pilot study of induction demonstrating the feasibility of substituting two cycles of topotecan and cyclophosphamide for two cycles of vincristine, cyclophosphamide, and doxorubicin. After a response to chemotherapy, resection of the primary tumor should be attempted, followed by myeloablative chemotherapy and stem cell rescue (i.e., bone marrow and/or peripheral blood stem cell transplantation). Whether or not harvested stem cells should be purged of neuroblastoma cells has been studied in a randomized fashion. There was no advantage to purging. Two or more sequential cycles of myeloablative chemotherapy and stem cell rescue given in a tandem fashion has been studied and feasibility was established.[7,18] It is now under clinical evaluation in COG. Radiation to the primary tumor site should be undertaken whether or not a complete excision was obtained. The optimal dose of radiation therapy has not been determined. Radiation of sites of metastatic disease is determined on an individual case basis. After recovery, patients are treated with oral 13-cis -retinoic acid for 6 months. Both myeloablative therapy and postchemotherapy retinoic acid improve outcome in patients categorized as high risk.[3,5] For high risk-patients in remission following HSCT, compared to retinoic acid alone, chimeric anti-GD2 antibody ch14.18 combined with granulocyte-macrophage colony stimulating factor and interleukin-2 and given in concert with retinoic acid improves EFS.