Interrupted vs. continued maintenance therapy in childhood acute leukemia.

A total of 313 patients with childhood acute leukemia received a combination of vincristine (2 mg/m2/week) and prednisone (60 mg/m2/day); 86% of 276 evaluable patients achieved a complete bone marrow remission in a median of 35 days. When a complete bone marrow remission was achieved, patients were randomized to one of three oral maintenance therapies: 6-mercaptopurine (6MP) (75 mg/m2/day), methotrexate (MTX) (25 mg/m2/twice weekly), or cyclophosphamide (CYC) (100 mg/m2/day). Patients receiving maintenance therapy were further randomized at 2 and 6 months after the start of maintenance either to continue or discontinue therapy. tthe median lengths of subsequent bone marrow remission for patients randomized at 2 months to continue vs. discontinue therapy were: 37 vs. 19 weeks for 6-MP patients; 25 vs. 14 weeks for MTX patients; and 29 vs. 13 weeks for CYC patients. The median lengths of subsequent marrow remissions for patients receiving maintenance therapy for 6 months and randomized to continue vs. discontinue were: 57 vs. 17 weeks for 6-MP patients; 60 vs. 40 weeks for MTX patients; and 23 vs. 10 weeks for CYC patients. Results indicate a significant advantage for continuing maintenance therapy at 2 and 6 months after the start of complete bone marrow remission.