Abnormalities of chromosome bands 15q13-15 in childhood acute lymphoblastic leukemia

Recurring breakpoints in chromosome bands 15q13-15 occur infrequently in leukemia. To the authors' knowledge, the clinical significance of these breakpoints in childhood acute lymphoblastic leukemia (ALL) has not been previously investigated.

Centrally reviewed karyotypes of children with newly diagnosed ALL enrolled on Children's Cancer Group protocols from 1988 to 1995 formed the basis of the current report. Statistical analyses used chi-square tests for homogeneity of proportions, and outcome was analyzed using life table methods and associated statistics.

Of 1946 cases with centrally reviewed and accepted cytogenetic analyses, 23 cases (1%) had breakpoints in chromosome bands 15q13-15. Most patients with 15q13-15 breakpoints had standard risk ALL, although breakpoints in 15q13-15 occurred more frequently in infants than in older children. The majority of these patients (16 patients; 70%) had balanced 15q13-15 rearrangements. Additional chromosomal abnormalities not involving 15q included abnormal 12p, abnormal 9p, Philadelphia chromosome, deletion 6q, and an 11q23 breakpoint. Thirteen (57%) 15q13-15 breakpoints occurred in pseudodiploid karyotypes; five (22%) were in hyperdiploid karyotypes with 47-50 chromosomes; two (9%) were in hyperdiploid karyotypes with > 50 chromosomes; and three (13%) were in hypodiploid karyotypes. Of the 23 patients with 15q13-15 breakpoints, 21 were survivors, 18 survived event-free for 2.2-9.3 years, and 3 were alive 1 to 3 years after a relapse at time of writing.

The current study suggests that genes at 15q13-15 may be involved in the leukemogenesis of some cases of childhood ALL, but that with current intensive therapy such aberrations do not confer increased risk of treatment failure.