Measurable Residual Disease and Clinical Outcomes in Chronic Lymphocytic Leukemia

Importance: Measurable residual disease (MRD) refers to the presence of disease at low levels not detected by conventional pathologic analysis. The association of MRD status as a surrogate end point of clinical outcome in chronic lymphocytic leukemia (CLL) has not been established in the era of targeted agents. Assessing the association of MRD with progression-free survival (PFS) may improve its role as a surrogate marker and allow its use to accelerate drug development. Objective: To assess the association between MRD and PFS in CLL using data from prospective clinical trials that studied targeted agents or obinutuzumab-based treatment. Data Sources: Clinical studies on CLL were identified via searches of PubMed, Embase, Scopus, and Web of Science from inception through July 31, 2023. Study Selection: Prospective, single-arm, and randomized clinical trials that assessed targeted agents or obinutuzumab-based treatment and reported PFS by MRD status were included. Studies with insufficient description of MRD information were excluded. Data Extraction and Synthesis: Study sample size, median patient age, median follow-up time, line of treatment, MRD detection method and time points, and survival outcomes were extracted. Main Outcomes and Measures: Analyses of survival probabilities and hazard ratios (HRs) were conducted for PFS according to MRD status. Meta-analyses were performed using a random-effects model. Results: A total of 11 prospective clinical trials (9 randomized and 2 nonrandomized) including 2765 patients were analyzed. Achieving undetectable MRD (uMRD) at 0.01% was associated with an HR of 0.28 (95% CI, 0.20-0.39; P < .001) for PFS. Median PFS was not reached in both groups (uMRD vs MRD), but the estimated 24-month PFS was better in the uMRD group (91.9% [95% CI, 88.8%-95.2%] vs 75.3% [95% CI, 64.7%-87.6%]; P < .001). The association of uMRD with PFS was observed in subgroup analyses in the first-line treatment setting (HR, 0.24; 95% CI, 0.18-0.33), relapsed or refractory disease setting (HR, 0.34; 95% CI, 0.16-0.71), and trials using time-limited therapy (HR, 0.28; 95% CI, 0.19-0.40). Conclusions and Relevance: The findings of this systematic review and meta-analysis suggest that assessing MRD status as an end point in clinical trials and as a surrogate of PFS may improve trial efficiency and potentially allow for accelerated drug registration.