The effect of 6-MP therapy on the duration of remissions induced by adrenal corticosteroids has been studied as a model for testing of new agents. Ninetytwo patients under age 20 entered the study and were accepted for analysis. Sixty-two (67 per cent) had complete or partial remissions induced by corticosteroids. Patients in remission were randomly assigned to maintenance therapy with either 6-MP or placebo. The median duration of 6-MP-maintained complete remissions was 33 weeks and for placebo, 9 weeks. A sequential experimental design was used to analyze remission times while the study was in progress. This resulted in the study being stopped after analysis of the remission times of 21 pairs of patients (42 patients). Overall survival was not significantly different for the two treatment programs, since patients maintained on placebo were treated with 6-MP when relapse occurred.
The activity of the known active antileukemic compound 6-MP was readily detected by this experimental design without compromise of optimal survival. Such a design should prove useful for the evaluation of new agents and also permit study of the remission maintenance activity of a compound separately from its remission inducing activity.