BACKGROUND AND METHODS. The authors studied the clinical and biologic features and treatment response of 358 children with acute lymphoblastic leukemia (ALL), including 90 adolescents, treated on a single multiagent protocol (St. Jude Total Study XI, 1984-1988). This was done to clarify whether the disease differed in adolescents and to determine the degree of improvement in treatment outcome produced by this modern intense chemotherapy.
Results: Compared with the younger children (1-9 years of age; infants 1 year old or younger excluded; n = 257), adolescents (10-18 years of age; n = 90) were significantly more likely to have adverse prognostic features, including T-cell phenotype, L2 blast cell morphologic characteristics, blasts with negative findings for common ALL antigen, and ploidy other than hyperdiploidy greater than 50. Eighty-six of the 90 (96%) adolescents achieved a complete remission, a rate similar to that of the children (97%). Although the event-free survival (EFS) of adolescents was shorter than that of younger children (5-year EFS of 66 +/- 8% versus 75 +/- 5%, respectively; P = 0.04), in this analysis of consecutively treated patients with ALL it showed a significant statistical and clinical improvement as compared with that in our previous study (St. Jude Total Study X, 1979-1983; 5-year EFS rate of 66 +/- 8% versus 37 +/- 5%, respectively; P < 0.001). Within the adolescent group treated on Total Study XI, the EFS was worse for those older than 15 years of age than for those 10-14 years old (46 +/- 15% versus 75 +/- 8%, respectively; P = 0.007). Toxic effects primarily included myelosuppression without severe sequelae. Approximately 96% of the therapy was administered in the outpatient setting.
Conclusions: The increased frequency of unfavorable clinical and biologic features undoubtedly accounts for the poorer prognosis of adolescents with ALL, a conclusion supported by the lack of independent prognostic importance of age in this study. The authors conclude that approximately two-thirds of adolescents can be cured when treated with this intensive but tolerable therapy, showing that this form of treatment significantly has changed the prognosis of adolescents with ALL.