Discontinuing therapy in childhood acute lymphoblastic leukemia treated with a chemoimmunotherapy protocol.

We examined the results of discontinuing therapy in Japanese children with acute lymphoblastic leukemia. Of the 209 patients in the chemoimmunotherapy study, 120 (57.4%) had all chemotherapy stopped after 3 years of complete remission, and 72 (34.4%) reached the point of discontinuing immunotherapy after 5 years of complete remission. Of the 120 children removed from chemotherapy, 14 (11.7%) have relapsed, mainly in the extramedullary sites (5: testis, 5: bone marrow, 3: central nervous system, 1: bone); relapses occurred 1-23 months after cessation of chemotherapy (median 11 months). Boys had higher post-chemotherapy relapse rate than girls (0.21 versus 0.08, P less than 0.05). None of the 72 children removed from immunotherapy have yet relapsed. Long-term remission and possibly cure can be expected in approximately one-half of newly diagnosed Japanese patients. Although the active immunotherapy had no beneficial effect on the overall outcome for leukemic children, it could be of benefit to the elimination of bone marrow relapses after cessation of chemotherapy.