Drug exposure and measurable residual disease in chronic lymphocytic leukemia: a systematic review

For fixed-duration therapies against chronic lymphocytic leukemia (CLL), undetectable measurable residual disease (MRD) predicts overall and progression-free survival more accurately than complete remission. For indefinite therapies, MRD status can direct discontinuation of treatment. We systematically reviewed the relationship between antineoplastic drug exposures and undetectable MRD in CLL. Seventeen trials from MEDLINE and EMBASE met the inclusion criteria; four of which evaluated drug exposures in relation to MRD status. Undetectable MRD was associated with higher trough concentrations of ofatumumab and alemtuzumab, as well as increased maximum concentration and area under the plasma concentration curve (AUC) of ibrutinib. One study found an association between high rituximab AUC and undetectable MRD until adjusting for tumor burden. The limited studies, lack of exposure measurements of concomitant drugs, and high heterogeneity in designs limit the results' generalizability. Further research is needed to explore the exposure-MRD relationship and the possibility for therapeutic drug monitoring in CLL.