The results of the first study of the Leukemia Chemotherapy Cooperative Study Group A for the evaluation of two treatment programs in acute leukemia are reported. The cases were accumulated in a period of 15 months. One hundred and twenty-five of the 168 patients started on the study were considered adequately treated and suitable for analysis. The 43 cases excluded from evaluation consisted of patients whose therapy was changed to steroids, those expiring while on treatment, and those lost for follow-up or drug errors. In 125 cases of previously untreated acute leukemia in children, no significant difference was seen in the percentage of complete remissions obtained when 6-mercaptopurine was used alone or when 6-mercaptopurine and azaserine were used in combination.
The duration of the remissions obtained with the combined therapy was not significantly longer than when 6-mercaptopurine was used alone.