Is MRD eradication a desirable goal in CLL?

Among chronic lymphocytic leukaemia (CLL) patients who require therapy, their response to therapy is the most important prognostic factor, with a better response predicting longer progression-free and overall survival. In this context, patients who achieve minimal residual disease (MRD)-negative status have better prognosis than those with inferior response to therapy, including those with MRD-positive complete response (CR). MRD can be assessed by either allele-specific polymerase chain reaction (PCR) or four-colour cytofluorometry. Importantly, methods to determine MRD in CLL have been standardised. Nevertheless, MRD status should not be used as a goal of therapy outside clinical studies. This is because the issue of the benefits of achieving MRD-negative status in patients with CLL requires further investigation in large controlled trials, in which patients should be stratified according to not only clinical variables but also biological parameters such as cytogenetics, IGHV mutations or ZAP-70 expression.