Treatment Response

Response BM Blasts (%) Neutrophils (x109/L) Platelets (x109/L) Comment
Complete remission (CR) <5% ≥1.0 ≥100 Absence of circulating blasts and blasts with Auer rods and extramedullary disease; MRD-positive or unknown
CR without MRD (CRMRD-) <5% ≥1.0 ≥100 If studied pretreatment, CR with negativity for a genetic marker by RT-qPCR or MFC; test method and sensitivity should be reported as sensitivities vary by marker tested and method used; analyses should be done in experienced laboratories
CR with incomplete hematologic recovery (CRi) <5% <1.0 <100 All CR criteria except for residual neutropenia or thrombocytopenia
Morphologic leukemia-free state (MLFS) <5% NA NA Absence of blasts with Auer rods and extramedullary disease; no hematologic recovery required; marrow should not merely be “aplastic”; at least 200 cells should be enumerated or cellularity should be at least 10%
Partial remission (PR) Decrease pre-treatment bone marrow blasts by 50%; decrease bone marrow blasts to 5%-25% ≥1.0 ≥100 All hematologic criteria of CR

There are several levels of response to treatment in AML (ie, CR, MLFS, and PR), and varying levels of CR based on hematologic recovery and MRD detection.1 A morphologic CR has been established as an early surrogate of long-term survival; patients who achieve CRi have inferior RFS and OS outcomes compared to patients who achieve CR. CRMRD- is now a defined response endpoint in AML due to the prognostic significance of MRD.2 MLFS can be used as an additional measure of clinical response in the context of clinical trials.2 In AML, a PR is generally expected to be short duration and unlikely to serve as a surrogate for clinical benefit.3

The European LeukemiaNet response criteria were published in 2010 and updated in 2016 to reflect advances in our understanding of the pathogenesis of AML, new developments in assays for genetic and cytogenetic testing, and the development of new treatments for AML; these new recommendations parallel the current update to the WHO classification of myeloid neoplasms and acute leukemia.1

References: 1. Döhner H, Estey E, Grimwade D, et al. Diagnosis and management of AML in adults: 2017 ELN recommendations from an international expert panel. Blood. 2017;129(4):424-447. 2. Bloomfield CD, Estey E, Pleyer L, et al. Time to repeal and replace response criteria for acute myeloid leukemia? Blood Rev. 2018;32(5):416-425. 3. Appelbaum FR, Rosenblum D, Arceci RJ, et al. End points to establish the efficacy of new agents in the treatment of acute leukemia. Blood. 2007;109(5):1810-1816.