Prognostic significance of cytogenetically detected chromosome 21 anomalies in childhood acute lymphoblastic leukemia: a Pediatric Oncology Group study.

Chromosome anomalies have been shown to have prognostic significance in children with acute lymphoblastic leukemia (ALL). Chromosome 21 was evaluated for its ability to predict outcome when found in either a single copy (the Mono21 group) or when involved in a structural aberration (the Misc21 group). Both anomalies were associated with an increased risk of failure for patients with standard-risk ALL, rather than higher-risk ALL. Event-free survival was 50.0% at 5 years and 48.4% at 8 years for standard-risk patients with Mono21+Misc21, compared with 77.8 and 75.5%, respectively, for standard-risk patients without these anomalies of chromosome 21. There was no significant difference in outcome between the Mono21 and the Misc21 group (P = 0.10). Mono21 and Misc21 were determined to be independently prognostic whether or not the primary leukemic clone had fewer than 45 chromosomes. The frequency of an adverse outcome was comparable to other poor prognosis subgroups such as hypodiploidy (<45 chromosomes), t(9;22), or t(4;11), all of which have been targeted for aggressive therapy even if the case is otherwise standard risk.