Three versus five years of maintenance therapy are equivalent in childhood acute lymphoblastic leukemia: a report from the Childrens Cancer Study Group.

Childrens Cancer Study Group protocol 141 (CCG-141), a randomized trial, was designed in part to compare 3 v 5 years of maintenance therapy, to evaluate the role of late reinduction, and to identify factors that predict relapse after 3 years of continuous complete remission (CCR) in acute lymphoblastic leukemia (ALL). Of 880 patients entered on study, 827 (94%) achieved complete remission and 499 (56.7%) were in CCR after 3 years of maintenance therapy. Boys were required to have negative testicular biopsies before randomization. A total of 481 patients were eligible for the duration of therapy phase of the study. Of the 310 (64.4%) randomly assigned patients, 101 were entered on regimen A: discontinue therapy; 105 on regimen B: reinduction for 4 weeks, then discontinue therapy; and 104 on regimen C: continue maintenance therapy for 2 more years, then discontinue. After a median follow-up of over 72 months, no significant differences in disease-free survival (DFS) or survival were noted in the three regimens. At 6 years from randomization, 93.0%, 89.1%, and 89.1% of patients on regimens A, B, and C, respectively, remained in CCR. Isolated CNS or overt testicular relapses were not significantly different in any of the study regimens. Isolated testicular relapse after a negative biopsy occurred in only two of 137 randomized males (1.5%). DFS (P = .10) and survival (P = .83) were not significantly different for all boys and girls randomized to regimens A, B, or C. The relapse rate was higher in boys than in girls randomized to discontinue therapy (11% v 4%), but the difference was not statistically significant (P = .14). Except for the presence of occult testicular leukemia (TL) in males, no other factors were identified that predicted for adverse events after 3 years of CCR. We conclude that prolongation of maintenance therapy beyond 3 years does not improve survival or decrease the risk of relapse.