The evolving use of minimal residual disease (MRD) assessment in chronic lymphocytic leukemia

The treatment of chronic lymphocytic leukemia (CLL) has changed remarkably throughout the past decade, with patients achieving deeper and more durable responses. Importantly, this clinical activity has been found to translate to prolonged survival. With some treatments, these responses are now allowing patients to stop therapy after 1 or 2 years, a concept referred to as "fixed duration." However, not all patients experience these outcomes. How to determine which patients can safely stop treatment remains unclear. Minimal residual disease (MRD) is emerging as a prognostic biomarker. In CLL, undetectable MRD has been shown to correlate with prolonged progression-free survival and, in some cases, overall survival. The incorporation of MRD status into clinical decision-making is not yet widely done, primarily based on the lack of prospective clinical trial data. As the endpoint of MRD status becomes more common in clinical trials of CLL, the role in the clinical setting will become more clear. Furthermore, prognostic models will help to determine the utility of MRD as a surrogate endpoint in clinical studies. This monograph examines clinical trial data regarding the role of MRD in CLL, and provides recommendations on how to incorporate MRD assessment into clinical management.