Clinical and biologic features predict a poor prognosis in acute lymphoid leukemias in infants: A pediatric oncology group study

Analysis of remission induction rates for 1,117 children 18 months to 10 years of age (group 1) and 90 infants <18 months of age (group 2) with acute lymphoid leukemia (ALL) and of duration of continuous complete remission (CCR) for 454 in group 1 and 33 in group 2 revealed that infants fared significantly worse in both measures of outcome (P = .03 and P < .0001). To examine potential reasons for the poor prognosis of affected infants, clinical and biologic features of their ALL were compared. Infants had higher WBC counts (P < .001), a higher incidence of massive splenomegaly (P < .001), massive hepatomegaly (P < .001), more central nervous system (CNS) disease at diagnosis (P < .01), and lower platelet counts (P < .001). Also, their blasts were less often PAS⁺ (P = .02). The incidence of non(T, B, pre-B), T and pre-B immunophenotypes of ALL did not differ significantly between the two groups. However, in patients with non(T, B, pre-B) ALL, the majority (51%) of infants had common ALL antigen (CALLA)-negative blasts, as compared with only 7% in group 1 (P < .001). Furthermore, infants with non(T, B, pre-B) cell ALL who were <12 months of age were almost always CALLA^- (18 of 21). The blasts of children from both groups usually expressed Ia-like antigens. These data illustrate that infants with ALL have extensive and bulky disease more often than do older children and are more often affected with a prognostically unfavorable phenotype of acute leukemia (AL) which expresses Ia-like antigens but is more often PAS^- and CALLA^-. We believe that these clinical and biological differences predict and explain in part the observed poor response to treatment of infants with ALL.