Intensive intravenous methotrexate and mercaptopurine treatment of higher-risk non-T, non-B acute lymphocytic leukemia: A pediatric oncology group study

Purpose: To determine the potential efficacy and toxicity of intravenous (IV) methotrexate (MTX) and mercaptopurine (MP) as postremission intensification treatment for children with B-lineage acute lymphoblastic leukemia (ALL) at higher risk to relapse. Patients and Methods: Eighty-three patients (age 1 to 20 years) with higher-risk B-lineage ALL were entered onto this protocol. Following standard four-drug remission induction, 80 patients received 12 intensive 2-week cycles of MTX/MP: MTX 200 mg/m² IV push, then 800 mg/m² IV 24-hour infusion on day 1; MP 200 mg/m² IV in 20 minutes, then 800 mg/m² IV 8-hour infusion day 2; MTX 20 mg/m² intramuscularly day 8; and MP 50 mg/ m² by mouth days 8 to 14. Age-based triple intrathecal therapy (MTX, hydrocortisone, and cytarabine) was administered for CNS prophylaxis. Continuation therapy was weekly MTX/MP (as on days 8 to 14) for 2 years. Results: Eighty-one patients (98%) entered remission. There were 28 relapses (marrow, n = 11; marrow and CNS, n = 2; isolated CNS, n = 9; testes, n = 5; ovaries, n = 1). No overt relapse occurred during the intensive phase of therapy. The event-free survival (EFS) rate at 4 years is 57.4% ± 9.1% (SE). Hematologic, mucosal, and infectious toxicities were seen in 12%, 9%, and 5% of intensive MTX/MP courses, but were generally mild. Conclusion: Combined data from this and our previous trial suggest that intensive MTX/MP may produce long-term disease-free survival in 70 to 75% of children with B-lineage ALL. In comparison to other intensive regimens, intensive MTX/MP is easy to administer, effective, and relatively nontoxic. If patients at risk for failure of MTX/MP can be identified prospectively, more aggressive regimens could be restricted to this smaller (25% to 30%) cohort.