Eradication of Measurable Residual Disease in AML: A Challenging Clinical Goal.

Abstract

Simple SummaryRelapse is still a major problem in AML because it occurs in about 60–80% of patients, even those who have previously achieved complete remission (CR), defined by the presence of ≤5% bone marrow (BM) leukemic cells. Thus, since CR is unable to predict the relapse risk, significantly more sensitive techniques aimed at identifying AML cells in BM or peripheral blood, a parameter termed measurable residual disease (MRD), have been developed. Among them, RT-qPCR, which analyses appropriate molecular markers, and multiparameter flow cytometry (MFC), which analyses aberrantly expressed antigens, have been identified as the methods of choice for MRD detection. Nowadays, various studies that assessed MRD by these techniques have provided compelling evidence that MRD positivity (MRD+) after standard induction/consolidation chemotherapy and before allo-HSCT is predictive of a very poor clinical outcome. In addition, other studies, which showed that MRD+ clearance even at late time points of the course of the disease may improve the disease clinical outcome, have further strengthened the relevance of MRD+. Thus, a complete MRD eradication, potentially attainable through novel innovative treatments, has emerged as an un-met clinical need in AML and is expected to improve our patients’ prognosis.In non-promyelocytic (non-M3) AML measurable residual disease (MRD) detected by multi-parameter flow cytometry and molecular technologies, which are guided by Consensus-based guidelines and discover very low leukemic cell numbers far below the 5% threshold of morphological assessment, has emerged as the most relevant predictor of clinical outcome. Currently, it is well-established that MRD positivity after standard induction and consolidation chemotherapy, as well as during the period preceding an allogeneic hematopoietic stem cell transplant (allo-HSCT), portends to a significantly inferior relapse-free survival (RFS) and overall survival (OS). In addition, it has become absolutely clear that conversion from an MRD-positive to an MRD-negative state provides a favorable clinical outcome similar to that associated with early MRD negativity. Thus, the complete eradication of MRD, i.e., the clearance of the few leukemic stem cells—which, due to their chemo-radiotherapy resistance, might eventually be responsible of disease recurrence—has become an un-met clinical need in AML. Nowadays, this goal might potentially be achieved thanks to the development of novel innovative treatment strategies, including those targeting driver mutations, apoptosis, methylation patterns and leukemic proteins. The aim of this review is to analyze these strategies and to suggest any potential combination able to induce MRD negativity in the pre- and post-HSCT period.