Prognostic factors in infants with acute myeloid leukemia.

Little is known about the factors that affect treatment outcome in very young children with acute myeloid leukemia (AML). We therefore analyzed the prognostic impact of various presenting clinical and laboratory features by discrete age group in 299 children with AML treated in four consecutive clinical trials between 1980 and 1997. Differences in presenting features, as well as treatment outcome, were compared between children aged 12 months or less (n = 28) or 13 to 24 months (n = 28) and those more than 24 months of age (n = 243). Children in the two youngest groups (24 months of age or less) had similar presenting features and treatment outcome. Collectively, these 56 children were significantly more likely than the 243 older patients to have M4 or M5 leukemia (70% vs 30%), CNS leukemia (33% vs 22%), the t(9;11) (p22;q23) (18% vs 6%) or other 11q23 translocations (23% vs 3%), and less likely to have Auer rods (2% vs 54%) or the t(8;21) (q22;q22) (0% vs 17%). Among patients aged 24 months or less, two factors independently predicted a favorable prognosis: FAB M4 or M5 leukemia (relative risk of relapse, 0.4; 95% confidence interval, 0.2-0.9) and the t(9;11) (relative risk, 0.3; 95% confidence interval, 0.1-1.0). Leukocyte count and 11q23 translocations other than the t(9;11) lacked prognostic significance. Among older patients, a leukocyte count <50 x 10(9)/l and the presence of the t(9;11) conferred a favorable prognosis.