Disomy 1 with terminal 1 p deletion is frequent in mass‐screening‐negative/late‐presenting neuroblastomas in young children,but not in mass‐screening‐positive neuroblastomas in infants

The mass screening (MS) of neuroblastoma has been undertaken in Japan by measuring urinary catecholamine metabolites in infants at the age of 6 months. To clarify the biological characteristics of MS‐positive (MS⁺) tumors in infants and MS‐negative (MS⁻)/late‐presenting tumors in young children, metaphase cytogenetic and/or interphase 2‐color FISH analyses using terminal 1p and pericentromeric 1q probes were performed on 246 (186 MS⁺ and 60 MS⁻) patients with neuroblastomas. The 246 tumors were classified into 4 groups on the basis of the constitution of chromosome 1; 22 tumors had disomy 1 with no 1p deletion (Dis1Norm1p); 41 tumors had disomy 1 or tetrasomy 1, all with the 1p deletion (Dis1Del1p); 164 tumors had trisomy 1, pentasomy 1, or a mixed population of cells with trisomy 1 and cells with tetrasomy 1, none with 1p deletion (Tris1Norm1p); 19 tumors with the same copy numbers of chromosome 1 as the Tris1Norm1p group, had 1p deletion (Tris1Del1p). mycn amplification was absent in the Dis1Norm1p and Tris1Del1p groups, frequent in the Dis1Del1p group (24/41), and rare in the Tris1Norm1p group (3/164) (p < 0.0001). Event‐free survival at 5 years was lowest 19.5%; 95% confidence interval (CI), 5.1–33.9] in the Dis1Del1p group, highest in the Tris1Norm1p (96.3%; 95% CI, 93.5–99.2) and Tris1Del1p (94.7%; 95% CI, 84.7–104.8) groups, and intermediate but varied (54.5%; 95% CI, 33.7–75.4) in the Dis1Norm1p group (p < 0.0001). Of the MS⁺ tumors, 90% were Tris1Norm1p or Tris1Del1p, and 55% of the MS⁻ tumors were Dis1Del1p. The finding that the Dis1Del1p tumors were frequent in MS⁻ but not in MS⁺ tumors suggests the limited efficacy of the MS program into reducing mortality from neuroblastoma. Int. J. Cancer 80:54–59, 1999. © 1999 Wiley‐Liss, Inc.