Beyond morphology: Minimal residual disease detection in acute myeloid leukemia

Purpose of review: Improved laboratory diagnostics over the past decade has resulted in identifiable genetic alterations and/or abnormal expression patterns in the majority of acute myeloid leukemia (AML). These leukemic patterns can then be monitored once patients achieve a morphologic remission. The role of various methodologies to detect minimal residual disease (MRD) in AML is reviewed, as well as the emerging role of MRD detection in prognostication and treatment decisions. Recent findings: Assessment of MRD in AML is now possible using updated methods including real-time quantitative PCR (RQ-PCR) for abnormal fusion transcripts, RQ-PCR for proteins known to be overexpressed in AML such as Wilms' tumor gene, and multiparameter flow cytometry to detect leukemia-associated phenotypes. Using these techniques, MRD analysis has shown value in terms of risk assessment, continued patient monitoring, and for therapeutic decision-making. Summary: MRD assessment can detect residual leukemia burden after treatment with improved sensitivity compared to morphology alone. There are now extensive data to support the prognostic value of MRD detection both after chemotherapy and in the pre and posttransplant setting, and emerging evidence to suggest there is a clinically relevant value to treatment decisions based on MRD results. The need for standardization of MRD technologies and interpretation is, thus, of critical importance.