The role of minimal residual disease in chronic lymphocytic leukemia.

Minimal residual disease (MRD) has evolved as a sensitive and highly prognostic surrogate parameter of response to therapy in chronic lymphocytic leukemia (CLL). Multiple methods have been established to measure and quantify MRD during and after therapy. The improved sensitivity of MRD measurements has made it possible to develop limited-duration therapies, first with chemotherapy and chemoimmunotherapy and now also with combined targeted therapy. Moreover, concepts to integrate MRD information beyond prognostication--to guide duration of treatment and determine sensitivity--are at present being explored in prospective trials. In this review, we summarize currently available methods of MRD detection, provide recent MRD data and outcomes from clinical trials in CLL, and discuss open questions and future approaches for MRD within and outside clinical trials.