Siimes, “Slow disappearance of peripheral blast cells: an independent risk factor indicating poor prognosis in children with acute lymphoblastic leukemia

The aim of this study was to find out whether the time required for disappearance of peripheral blast cells. or blast clearance. could be used to identify patients with a slow response to treatment associated with a poor progno-sis of acute lymphoblastic leukemia (ALL). Our series consisted of 1 58 children with newly diagnosed ALL. The mean follow-up time was 69 months (range 22 to 140 months). Blast clearance was significantly associated with length of event-free survival. Only two of nine children with blast clearance 2 weeks and 4 of 1 1 children with blast clearance of 1 1 to 1 3 days were in remission at the time of analysis as compared with 86 of 1 38 of the children with M ORE THAN 20 factors have been reported to influence the prognosis of children with acute lym-phoblastic leukemia (ALL).”3 Children who respond slowly to induction therapy, however, ie, who have M2 bone marrow morphology at day 14, have a poor prognosis despite other possible favorable characteristics.4’5 These patients appear to form a special group that should be identified and perhaps treated differently. The response to therapy can be assessed in different ways. Bone marrow examination is an invasive procedure that cannot be performed often. Assessment of the patient’s general condition may be clinically helpful, but lacks accu-racy and specificity. The response could also be judged from the decrease in total peripheral WBC count and, for exam-ple, the time of occurrence of the nadir of leukopenia. We have studied whether it is possible to combine the precision of bone marrow examination with the simplicity of WBC determination by counting the blast cells in the peripheral blood. The disappearance of blast cells from the peripheral blood, or blast clearance, was used as a criterion to identify patients with a slow response and to assess the relative risk of death or relapse in individual patients