Early clearance of peripheral blasts measured by flow cytometry during the first week of AML induction therapy as a new independent prognostic factor: a GOELAMS study

An early appreciation of treatment efficacy could be very useful in acute myeloblastic leukemia (AML), and a prognostic value has been suggested for the morphological assessment of decrease in blasts during induction therapy. More sensitive, multiparametric flow cytometry (FCM) can detect far lower blast counts, allowing for a precise and reliable calculation of blast cell decrease rate (BDR). Such a multiparametric FCM four-colours/single-tube protocol, combining CD11b, CD45-ECD and CD16-PC5, was applied to peripheral blood samples from 130 AML patients, collected daily during induction chemotherapy. Normalized blast cell percentages were used to calculate the relevant decrease slopes. Slope thresholds (−15), or the time required to reach 90% depletion of the peripheral blast load (5 days), was strongly associated with the achievement of complete remission ( P