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

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. 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. 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). Tumor cell ploidy may be a clinically useful factor for prognostication and treatment stratification in children with MYCN-amplified, favorable-stage NB tumors.