Minimal Residual Disease Is a Predictor for Progression-Free and Overall Survival in Chronic Lymphocytic Leukemia (CLL) That Is Independent of the Type or Line of Therapy.

The depth of remission in CLL correlates with survival in a large number of trials regardless of the therapy used and the depletion of minimal residual disease (MRD), when reported, is usually associated with improved progression free and overall survival. However it is not clear whether this improved outcome is due to the attainment of MRD negativity or whether MRD eradication is a surrogate for other variables that predict for good response. In order to address the true impact of achieving MRD negativity we present data from 137 patients with CLL who were treated between 1996 and 2007, achieved a good clinical response and had bone marrow examined post-therapy to assess remission status including MRD. The MRD assessment was performed in a single laboratory (HMDS, Leeds, UK) using multicolor flow cytometry capable of detecting minimal residual disease (MRD) to a level of one CLL cell in 10000 leukocytes as recently recommended in the IWCLL Guidelines.