Prognostic value of persistent peripheral blood and bone marrow lymphoblasts on day 15 of therapy in childhood acute lymphoblastic leukemia as detected by flow cytometry.

AIM The predictive value of residual disease measured by flow cytometry at day 15 of induction therapy was analyzed in 182 children treated for acute lymphoblastic leukemia (ALL). MATERIALS AND METHODS Peripheral blood (PB) and bone marrow were assessed for leukemia cells by morphology and flow cytometry at days 0, 8, and 15. RESULTS Absolute blast count (ABC) >200/μl in PB by day 15 assessed by flow cytometry predicted a lower probability of disease free survival (pDFS) (p=0.056). Patients with bone marrow lymphoblast (BML)>0.5% had a lower pDFS (p=0.002). Cumulative relapse incidence for patients with BML<0.5% was 8.9% vs. 47.1% (OR=4.6, p=0.036). In common/pre-B-ALL patients aged >10 years with BML>0.5%, pDFS value was significantly lower. In the multivariate analysis, the only significant factor with adverse prognostic value for pDFS was BML>0.5% (HR=5.3 p=0.030). CONCLUSION BML>0.5% analyzed by flow cytometry at day 15 is possibly the strongest prognostic factor in pediatric ALL.