Day 14 Measurable Residual Disease As a Predictor of Post-Induction Response in Patients with Acute Myeloid Leukemia
Authors: Martín-Rojas Reyes María , Badiola Jon , Silva De Tena Pablo , Pérez-Corral Ana , Gómez-Centurión Ignacio , Rodríguez-Macias Gabriela , Ballesteros Mónica , Martínez-Laperche Carolina , Font Lopez Patricia , Pérez-Sánchez Isabel , Buño Ismael , Anguita Javier , Kwon Mi , Diez-Martin Jose L. 
Published: November 2021

Abstract
INTRODUCTION
Several studies have shown that morphological remission at day 14 is a predictor of post-induction response in patients with acute myeloid leukemia (AML) undergoing an intensive treatment. However, the role of measurable residual disease (MRD) by multiparameter flow cytometry (MFC) at day 14 remains unknown. The aim of our study is to explore the role of MRD at day 14 and its association with outcomes of patients with AML undergoing an intensive treatment.
METHODS
We conducted a retrospective study in adult patients with newly a diagnosed AML in our center between 2007 and 2020. Adult patients who received intensive chemotherapy, excluding those with an acute promyelocytic leukemia, were included. Bone marrow aspiration was performed at day 14 after induction to assess morphological response and MRD by MFC. Early blast clearance (EBC) was defined as &lt;5% of blasts and negative MRD was defined as &lt;0.1% abnormal cells within mononucleated cells by MFC. Day 14 aspiration findings were compared with clinical data. This study was approved by our Institutional Ethics Committee. Data were analyzed using IBM SPSS Statistics version 24.
RESULTS
A total of 131 patients were analyzed. Median age was 55.6 years (IQR 42.3-64.2). The most frequent AML subtype was AML with myelodysplasia-related changes (34.4%), followed by NPM1-mutated AML (32.1%). The most commonly used induction regimen was "7+3" (96.2%) (Table 1).
On day 14 bone marrow aspiration, median cellularity was 0.5/5 (IQR 0.5-1). 107 patients (81.7%) showed a blast reduction &gt;50% compared to diagnosis and 87 patients (66.4%) had less than 5% of blasts. In this latter group, 28.6% of patients had a positive MRD and 71.4% had a negative MRD. NPM1-mutated AML showed the highest EBC rates while AML with myelodysplasia-related changes had the lowest rates (83.3% versus 55.5%; p=0.04). Furthermore, there were statistically significant differences in EBC rates based on the 2017 European Leukemia Net risk stratification, with 80% of EBC in low risk, 66.6% in intermediate risk and 53.4% in high risk AML (p=0.038). No differences were observed in MRD at day 14 based on AML subtypes or risk stratification.
We subsequently analyzed the negative (NPV) and positive predictive values (PPV) of day 14 bone marrow aspiration results by morphology and MFC to predict post-induction results. As a predictor of post-induction CR, day 14 EBC had a NPV of 82% and a PPV of 69%, while day 14 MRD had a NPV of 86% and a PPV of 49%. However, for predicting post-induction MRD, day 14 EBC had a NPV of 49% and a PPV of 15%, while day 14 MRD had a NPV of 71% and PPV of 74%.
The correlation between day 14 and post-induction bone marrow aspiration is shown in Table 2. Bivariate analysis showed that achieving CR with negative MRD in post-induction bone marrow aspiration was associated with EBC (p&lt;0.001) and negative MRD (p=0.04) at day 14 bone marrow aspiration. No statistically significances were observed based on marrow cellularity. A multivariate analysis using logistic regression showed that negative MRD by MFC at day 14 was the only independent predictor variable to achieve post-induction CR with negative MRD (OR 4.95% CI 1.0-15.9; p=0.04).
CONCLUSION
Patients showing EBC with negative MRD on day 14 bone marrow aspiration are more likely to achieve post-induction CR with negative MRD, with day 14 MRD by MFC being the only independent factor able to predict post-induction CR with negative MRD in our cohort. However, further prospective studies are needed to confirm our findings.
Figure 1 Figure 1.

Disclosures
Martín-Rojas: Celgene-BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees. Kwon: Novartis, Celgene, Gilead, Pfizer: Consultancy, Honoraria.