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 (K(w) = 0.737, p < 0.001, and r(s) = 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.