Cytogenetics of Hispanics and Whites with Childhood Acute Lymphoblastic Leukemia in California.

Epidemiologic studies of childhood leukemia have made limited use of tumor genetic characteristics, which may be related to disease etiology. We characterized the cytogenetics of 543 childhood leukemia patients (0–14 years of age) enrolled in the Northern California Childhood Leukemia Study, an approximately population-based study comprised primarily of Hispanics (42%) and non-Hispanic whites (41%), and compared the cytogenetic profiles between these two ethnic groups. Subjects were classified by immunophenotypes, conventional cytogenetic characteristics, and fluorescence in situ hybridization findings. The abnormalities most frequently observed among all patients were pseudodiploidy and high hyperdiploidy (51–67 chromosomes) (27% and 25%, respectively). No ethnic differences in the frequency of 11q23/MLL rearrangements were observed between Hispanics and non-Hispanic whites. Among B lineage ALL patients without 11q23/MLL rearrangements, the percentage of TEL-AML1 translocations was significantly lower in Hispanics (13%) than in non-Hispanic whites (24%; P = 0.01). This is the first large study to compare frequencies of cytogenetic events of primarily Hispanic and non-Hispanic white childhood leukemia patients. Our data suggest some cytogenetic characteristics likely differ between non-Hispanic whites and Hispanics. The mechanistic basis for the two-fold variation in frequency of TEL-AML1 may be due to ethnic-specific risk factors or genetics and should be explored further. Owing to the heterogeneity of leukemia in children, it is possible that cytogenetic subgroups may have distinct etiologies and risk factors which otherwise would be overlooked with the broad leukemia subtypes (e.g. ALL, AML) presently used in epidemiologic analyses.