Clinical significance of MYCN amplification and ploidy in favorable-stage neuroblastoma: A report from the Children's Oncology Group

Purpose: MYCN amplification is rarely detected in patients with favorable-stage neuroblastoma (NB). To determine the clinical significance of MYCN amplification in children with favorable-stage NB, we performed a retrospective review of data from the Pediatric Oncology Group (POG) biology study 9047. Patients and Methods: MYCN status, tumor cell ploidy, treatment, and outcome of patients with stage A, B, or Ds NB, enrolled on POG 9047 between 1990 and 1999 were analyzed. Event-free survival (EFS) and overall (OS) survival rates were analyzed using the Kaplan-Meier method. Results: Of the 1,667 patients enrolled on POG 9047, 643 had favorable-stage disease. Of these, follow-up data were available on 568 (34%) with stage A, B, or Ds disease and normal MYCN copy number, and 32 (1.9%) patients with MYCN-amplified, stage A, B, or Ds tumors. Within the cohort lacking MYCN amplification, the 7-year EFS and OS rates (± SE) were 91% ± 1% and 96% ± 1%, respectively. Patients with MYCN amplification had significantly worse EFS and OS (50% ± 9% and 59% ± 9%, respectively, P < .0001). Within the cohort of children with MYCN amplification, the 7-year EFS and OS rates were 80% ± 10% and 87% ± 9%, respectively for patients with hyperdiploid tumors and 25% ± 11% and 38% ± 12% for patients with diploid/hypodiploid NBs (P = .0063 and P = .0074, respectively). Conclusion: Tumor cell ploidy may be a clinically useful factor for prognostication and treatment stratification in children with MYCN-amplified, favorable-stage NB tumors.