Prognostic impact of day 15 blast clearance in risk-adapted remission induction chemotherapy for younger patients with acute myeloid leukemia: long-term results of the multicenter prospective LAM-2001 trial by the GOELAMS study group.

Early response to chemotherapy has a major prognostic impact in acute myeloid leukemia patients treated with a double induction strategy. Less is known about patients treated with standard-dose cytarabine and anthracycline. We designed a risk-adapted remission induction regimen in which a second course of intermediate-dose cytarabine was delivered after standard "7+3" only if patients had 5% or more bone marrow blasts 15 days after chemotherapy initiation (d15-blasts). Of 823 included patients, 795 (96.6%) were evaluable. Five hundred and forty-five patients (68.6%) had less than 5% d15-blasts. Predictive factors for high d15-blasts were white blood cell count (P<0.0001) and cytogenetic risk (P<0.0001). Patients with fewer than 5% d15-blasts had a higher complete response rate (91.7% vs. 69.2%; P<0.0001) and a lower induction death rate (1.8% vs. 6.8%; P=0.001). Five-year event-free (48.4% vs. 25%; P<0.0001), relapse-free (52.7% vs. 36.9%; P=0.0016) and overall survival (55.3% vs. 36.5%; P<0.0001) were significantly higher in patients with d15-blasts lower than 5%. Multivariate analyses identified d15-blasts and cytogenetic risk as independent prognostic factors for the three end points. Failure to achieve early blast clearance remains a poor prognostic factor even after early salvage. By contrast, early responding patients have a favorable outcome without any additional induction course. (ClinicalTrials.gov identifier NCT01015196).