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 less than 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 less than .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 less than .001), a higher incidence of massive splenomegaly (P less than .001), massive hepatomegaly (P less than .001), more central nervous system (CNS) disease at diagnosis (P less than .01), and lower platelet counts (P less than .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 less than .001). Furthermore, infants with non(T, B, pre-B) cell ALL who were less than 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.