Abstract
Chromosomal alterations in 1p36 were investigated in 196 neuroblastoma tumors using fluorescence in situ hybridization. Additionally, by using the same technique, it was determined whether MYCN was amplified in 149 of these. The most frequent finding was a deletion in 1p36, leading to monosomy of this region (29 cases, 15%). Furthermore, we found tumors with at least two intact copies of chromosome 1 and additional 1p36βdeleted copies. Altogether, 21 tumors (11%) displayed this imbalance of 1p36. Similar to the cases with deletion, imbalances were predominantly found in stage 4 tumors (81%), and they were significantly associated with an increased patient age (P = 0.01). Nearly all 1pβdeleted tumors showed amplification of MYCN (24/27 analyzed samples, 89%), whereas only 8 of 21 (38%) with imbalance did. Eight cases with imbalance were investigated for loss of heterozygosity (LOH) using microsatellite markers in 1p35β36. Only 4 displayed 1p36 LOH, whereas the remaining 4 were heterozygous. Both patients with deletion of 1p and with imbalance had a poor outcome [3βyear rate of eventβfreeβsurvival (EFS): 33Β±15% and 41Β±15%], which was significantly worse compared to the outcome of patients without 1p alterations (3βyear EFS: 70Β±5%; P = 0.01 and P = 0.0059). We conclude that besides monosomic short arm deletions, imbalance of 1p36 is a strong marker of a poor prognosis in neuroblastoma and not necessarily associated with MYCN amplification and LOH. Β© 2002 WileyβLiss, Inc.