Comparison of prednisolone, vincristine, methotrexate and 6-mercaptopurine vs. 6-mercaptopurine and prednisone maintenance therapy in childhood acute leukemia: a Southwest Oncology Group Study.

The study was designed to compare the relapse rate and toxicity of intermittent prednisone, oncovin (vincristine), methotrexate, and 6-mercaptopurine (POMP) vs. 6-mercaptopurine daily and a prednisone pulse every three months (PIP) for maintenance therapy in acute leukemia. Children with acute lymphoblastic, acute undifferentiated, or acute stem-cell leukemia were stratified on the basis of initial leukocyte count and age, then randomly assigned to POMP or PIP maintenance therapy. All patients received cranial irradiation and intrathecal chemotherapy. Of the 67 patients receiving POMP maintenance, 20(30%) remain in continuous remission. The median length of continuous remission achieved with POMP therapy was 49 weeks. Of 80 patients receiving PIP maintenance, 25(31%) remain in remission. The median length of continuous remission for PIP was 62 weeks. Of the possible prognostic factors evaluated, the only significant factor was the prognostic grouping base in age and initial leukocyte regimen was associated with a higher incidence of toxic reactions, frequently causing therapy interruption. The results for both regimens as studied are inferior to those for 6-mercaptopurine methotrexate maintenance regimens as reported by others.