Evaluation of bone marrow aspirates in patients with acute myeloid leukemia at day 14 of induction therapy

BACKGROUND Early assessment of response to chemotherapy in acute myeloid leukemia may be performed by examining bone marrow aspirate (BMA) or biopsy (BMB); a hypocellular bone marrow sample indicates adequate anti-leukemic activity. We sought to evaluate the quantitative and qualitative assessment of BMA performed on day 14 (D14) of chemotherapy, to verify the inter-observer agreement, to compare the results of BMA and BMB, and to evaluate the impact of D14 blast clearance on the overall survival (OS). METHODS A total of 107 patients who received standard induction chemotherapy and had bone marrow samples were included. BMA evaluation was performed by two observers using two methods: quantitative assessment and a qualitative (Likert) scale. ROC curves were obtained correlating the BMA quantification of blasts and the qualitative scale, by both observers, with BMB result as gold-standard. RESULTS There was a significant agreement between the two observers in both the qualitative and quantitative assessments (Kw = 0.737, p < 0.001, and rs = 0.798, p < 0.001; ICC = 0.836, p < 0.001, respectively). The areas under the curve (AUC) were 0.924 and 0.946 for observer 1 and 0.867 and 0.870 for observer 2 for assessments of the percentage of blasts and qualitative scale, respectively. The best cutoff for blast percentage in BMA was 6% and 7% for observers 1 and 2, respectively. A similar analysis for the qualitative scale showed the best cutoff as "probably infiltrated". Patients who attained higher grades of cytoreduction on D14 had better OS. CONCLUSIONS Evaluation of D14 BMA using both methods had a significant agreement with BMB and between observers, identifying a population of patients with poor outcome.