Slow disappearance of peripheral blast cells: an independent risk factor indicating poor prognosis in children with...

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 prognosis of acute lymphoblastic leukemia (ALL). Our series consisted of 158 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 greater than or equal to 2 weeks and 4 of 11 children with blast clearance of 11 to 13 days were in remission at the time of analysis as compared with 86 of 138 of the children with more rapid blast clearance. The respective 5-year event-free survivals were 17%, 36%, and 60% (P = .003). Multivariate analysis showed that the relative risk of death or relapse in patients with blast clearance of greater than 10 days was 5.2-fold (95% confidence limits 2.1 to 13.1) as compared with the others (P less than .001). Our results indicate that patients with a slow response to treatment can be identified by simple differential peripheral cell counts during the early induction phase well before or even instead of performance of a more invasive bone marrow aspiration.