Defining the correct role of minimal residual disease tests in the management of acute lymphoblastic leukaemia.

Minimal residual disease (MRD) has acquired a prominent role in the management of childhood and adult Acute Lymphoblastic Leukaemia (ALL) for its high prognostic value. Several studies have demonstrated the strong association between MRD and risk of relapse in childhood and adult ALL, irrespective of the methodology used. MRD is now used in clinical trials for risk assignment and to guide clinical management. Negativity at early time points may be considered to decrease treatment burden in patients who are likely to be cured with reduced intensity regimens. On the other hand, high MRD levels at late time points (end of consolidation) define ALL subgroups which deserve investigation of more effective treatments. The predictivity of MRD as a measurement of drug response in vivo opened new perspectives for its use in clinical decision, to deliver risk-based treatments, and possibly as a surrogate for efficacy in the evaluation of novel therapeutic approaches.