Yield of unpredicted bone-marrow relapse diagnosed by routine marrow aspiration in children with acute lymphoblastic leukaemia. A report from the Children's Cancer Study Group.

1466 children with acute lymphoblastic leukaemia had routine bone-marrow aspiration at the end of each 84-day cycle of maintenance therapy. Relapses detected by routine bone-marrow aspiration were classified according to whether or not they could be predicted by clinical signs or peripheral blood counts. In the low-risk, moderate-risk, and high-risk leukaemic patients 0.4%, 0.5%, and 0.8%, respectively, of the total routine bone-marrow aspirations yielded an unpredicted bone-marrow relapse. 19.4% of relapses were detected by routine surveillance marrow aspirations before any clinical signs of relapse on physical examination or peripheral blood count. The median survival after relapse in the predicted group was significantly shorter than that in the unpredicted group, but the eventual outcome was the same in both groups, 95% of all patients dying within 24 months of relapse.