The percentage of peripheral blood blasts on day 7 of induction chemotherapy predicts response to therapy and survival in patients with acute myeloid leukemia

Background Rapid clearance of peripheral blood blasts(PBBs) predicts complete remission(CR) and survival in patients with acute myeloid leukemia(AML). We aimed to explore the correlation between induction therapy response, outcome, and the PBB percentage. Methods Forty-six consecutive patients with de novo AML(excluding acute promyelocytic leukemia) were enrolled in this study. Flow cytometry was performed to identify cells with a leukemia-associated aberrant immunophenotype in the initial bone marrow aspirate and in peripheral blood on day 7 of induction therapy. Results The PBB percentage on day 7(D7PBBP) was significantly lower in patients who achieved CR(0.03%(0.0%, 0.45%)) than in those who did not(10.85%(1.13%, 19.38%); u =–3.92, P <0.001). The CR rate was significantly higher among patients with a D7 PBBP of <0.945%(84.62%, 22/26) than among those with a D7 PBBP of ≥0.945%(25.0%, 5/20; χ2 = 16.571, P <0.001). D7 PBBP was significantly correlated with overall survival(OS; r=–0.437, P=0.003) and relapsefree survival(RFS; r=–0.388, P=0.007). OS and RFS were significantly higher in patients with a D7 PBBP of <0.43% than in those with a D7 PBBP of ≥0.43%(P <0.001 and P=0.039, respectively). D7 PBBP was also found to be an independent prognostic indicator in multivariate analysis for both OS(P=0.036) and RFS(P=0.035). Conclusion D7 PBBP may be an important risk factor for the achievement of complete remission, for overall survival, and for relapse-free survival.