A reappraisal of the results of stopping therapy in childhood leukemia.

We examined the results of stopping therapy in children with acute lymphocytic leukemia. Of 639 patients in eight consecutive "total therapy" studies, 278 (44 per cent) had all treatment stopped, usually after 2 1/2 years of complete remission. About one fifth (55 of 278) of this group have relapsed, mainly in the bone marrow. The relapse rate for the first year off therapy was higher than that for the next three years (0.16 vs. 0.04, P less than 0.01). The life-table estimates of the four-year relapse rates were 0.24 for all patients and 0.22 for patients receiving adequate central-nervous system prophylaxis. Boys had a higher relapse rate than girls (0.33 vs. 0.15 P less than 0.01). None of the 79 patients who remained in complete remission for at least four years off therapy have yet relapsed. Acute lymphocytic leukemia appears curable in over one third of all newly diagnosed patients who receive treatment for approximately 2 1/2 years.