Speed of relapse in children with acute lymphoblastic leukaemia.

16 children with acute lymphoblastic leukaemia (ALL) who relapsed on maintenance treatment between September 1978 and December 1981 were studied. Their previous bone marrow aspirates were reviewed to determine the first evidence for marrow relapse and the subsequent rate of evolution of the disease. 60% of children had bone marrow evidence of unsuspected relapse at 8 wk, and 40% had evidence at 12 wk before clinical or peripheral blood relapse occurred. Early detection of relapse will prevent continued use of ineffective maintenance chemotherapy and may also reduce morbidity during subsequent induction therapy. Regular 8-weekly marrow aspirates are therefore recommended during first remission of ALL in children with a histocompatible sibling who would be eligible for bone marrow transplantation in second remission.