Minimal Residual Disease and Survival Outcomes in Patients With Chronic Lymphocytic Leukemia: A Systematic Review and Meta-analysis

Background Patients with chronic lymphocytic leukemia (CLL) who achieve undetectable minimal residual disease (U-MRD) (ie, < 10-4 detectable leukemic cells in peripheral blood or bone marrow) have better outcomes than those with detectable MRD. To assess the magnitude of improvement of progression-free survival (PFS) or overall survival (OS) in patients who achieved U-MRD after upfront chemotherapy (CT) or chemo-immunotherapy (CIT), we conducted a systematic review and meta-analysis. Materials and Methods The screening process adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Guidelines. The search strategy yielded 365 records, including 22 articles assessed for eligibility. Results Eleven studies comprising 2457 patients with CLL treated in upfront with CT or CIT were considered suitable for inclusion in the quantitative meta-analysis. Nine studies (n = 2088) provided data on the impact of MRD on PFS and 6 (n = 1234) on OS. MRD was the main endpoint in only 2 of these studies (n = 213). Tests of heterogeneity revealed significant differences among studies for PFS and OS, which highlights differences across studies. U-MRD status was associated with significantly better PFS overall (P < .001) and in patients who achieved conventional complete remission (P = .01). Regarding OS, U-MRD predicted longer OS globally (P < .001) but not in patients having achieved complete remission (P = .82). Conclusions U-MRD status after treatment with CT or CIT in newly diagnosed CLL is associated with long-term survival. These findings provide quantitative evidence to support the integration of MRD assessment as an end point in clinical trials of CLL.