Measurable residual disease after venetoclax treatment for relapsed or refractory chronic lymphocytic leukemia in Japan.

Measurable residual disease (MRD), defined as the persistence of minimal levels of leukemic cells following therapeutic intervention, serves as a pivotal prognostic biomarker in patients with chronic lymphocytic leukemia (CLL). We conducted a multicenter, cross-sectional study to assess MRD in Japanese patients with relapsed or refractory CLL. All patients received venetoclax-based therapy for 24 months. MRD in peripheral blood (PB) and bone marrow was assessed by multicolor flow cytometry using surface markers, including kappa and lambda light chains of surface immunoglobulins. The primary and secondary outcomes were the proportions of patients who achieved undetectable MRD (uMRD, < 10 CLL cells) and low-MRD (< 10 and ≥ 10 CLL cells) after 24 months of venetoclax treatment. From June 2023 to December 2024, 60 patients were enrolled, and 51 were analyzed. The median age was 78 years, and 68.6% were male. Thirty-four of 51 patients (66.7%) achieved uMRD, and 8 (15.7%) achieved low-MRD in PB after at least 24 months of venetoclax treatment. Assessment of MRD in PB by flow cytometry is helpful for evaluating treatment response, informing clinical decision-making, and predicting long-term outcomes in clinical practice. Further analyses are warranted to investigate the use of MRD in treatment decision-making and prognostication.Kindly check the inserted city in affiliations 5 and 9.The city names were corrrected.