Abstract
Among 1, 442 children (< 15 years old) with acute lymphoblastic leukemia (ALL) entered in the Children's Cancer and Leukemia Study Group (CCLSG) protocols from 1981 to 1998, the patients' characteristics of sex, leukocyte counts, chromosomal abnormalities, and immunophenotypes were studied by the presenting ages of eight groups. Leukocyte counts were significantly different between the different age groups (p < 0.0001) : the median value of all cases was 9, 900/y1, and the largest value was 100, 500/y1 in the group of 1-5 months ; the least one was 8, 400/p1 in the group of 5-7 years. Although the entire male-to-female ratio was 1.42, the two groups of 1-5 months and 12-17 months showed a significantly higher incidence of girls (0.55 and 0.71, p < 0.05). The t (4 ; 11) (q21 ; q23) chromosomal abnormality was identified in 14 (2.5%) of 541 patients, and half was detected in the youngest (< 6 months) group. The t (9 ; 22) (Ph 1+) patients were identified in 1.8% (10/541) and were less specific to a particular age group. T-cell ALL was detected in 9.5% (70/735) and was mostly frequent (17%) in the oldest age (11-14 years) group. Approximately 70% of the patients with these chromosomal abnormalities or T-cell phenotypes had more than 50, 000/, ul leukocytosis. Even in patients with B-precursor ALL without 11q23 and t (9 ; 22) abnormalities, leukocyte counts were significantly different between the different age groups (p <0.01). These results suggest that although the incidence of the particular chromosomal abnormalities or surface immunophenotypes of childhood ALL partly accounts for the difference in the patients' characteristics, other biological factors must affect their clinical features.
