Should evaluation for minimal residual disease be routine in acute myeloid leukemia?

In patients with acute myeloid leukemia (AML), measuring response to treatment is essential to guide clinical decisions. Methods for detecting disease beyond the resolution limit of morphology (i.e., minimal residual disease, MRD) are now widely available. We here discuss their merits and the results of side-to-side comparisons.

The ever-increasing comprehension of the molecular genetics of AML has led to the identification of targets for molecular monitoring of MRD in the majority of AML cases. Likewise, virtually all cases express aberrant immunophenotypes suitable for MRD monitoring by flow cytometry, a progress bolstered by powerful new-generation instruments. The clinical significance of MRD monitoring by either approach has been corroborated by recent results. However, with few exceptions, most of the studies continue to rely on retrospectively determined cut-off levels and time points. Moreover, when applied in parallel, the two approaches have yielded contradictory results.

MRD monitoring can help predicting the risk of relapse better than morphology and also provide endpoints for clinical testing of experimental agents. MRD can be applied to guide therapy but one must carefully consider the characteristics of the methods used and the degree of expertise of the laboratory performing the test.