Three to ten years after cessation of therapy in children with leukemia

Therapy was stopped in 140 children with acute lymphocytic leukemia after 2–3 years of complete remission (CR). Of the 108 children who had received preventive central nervous system (CNS) therapy and were in initial CR when therapy was stopped, 85 (79%) remain in CR for a median time of 93 months (66–166) and have been off therapy for a median time of 58 months (36–128). The 23 relapses involved the bone marrow in all but four patients who had isolated testicular relapse. Six of seven children who were in initial CR, but had received no CNS therapy, relapsed after cessation of therapy; five relapses involved the CNS. Twenty‐five children had at least one extramedullary relapse, usually in the CNS, with subsequent CR for 2–3 years before therapy was stopped; 18 of 25 (72%) remain in CR for a median time of 86 months (56–141) and have been off therapy for a median time of 56 months (33–103). Six of the seven relapses involved the marrow. No feature present at the time of diagnosis could be correlated with the frequency of relapse after cessation of therapy except for the significantly greater frequency among boys (25/75) than girls (11/67). The adequacy of therapy, especially CNS prophylaxis, was a positive factor. The hematologic recovery pattern and degree of rebound marrow lymphocytosis after cessation of therapy did not correlate with the frequency of subsequent relapse. Of the 36 patients who relapsed after cessation of therapy, all attained CR again and six are off therapy a second time for 3–21 months.