Evaluation of Rituximab interference with chronic lymphocytic leukemia ERIC MRD assay

CYTO 2024 -- Chronic lymphocytic leukemia (CLL) is the one of the most frequent types of leukemia in western countries and mainly occurs in elderly patients. This type of cancer has an overall survival of 5 years that ranges from 20% among very high-risk patients to more than 90% in those with less-aggressive genetic risk features. With the advent of new cancer immunotherapies such as Rituximab, an anti-CD20 antibody, many B-CLL patients are achieving complete remission. As a result, the quantification of minimal residual disease (MRD) is becoming increasingly important as an independent predictor of progression-free and overall survival in CLL. Flow cytometry is a key test to confirm CLL diagnosis, and the European Research Initiative on CLL (ERIC) was the first to introduce a consensus panel to assess MRD for CLL disease. Following ERIC recommendations, Labcorp has validated a CLL MRD assay to determine MRD levels with high sensitivity in patient samples. The Labcorp CLL ERIC MRD flow cytometry assay uses a combination of antibodies to detect B-CLL cells including CD20. Therefore, we assessed whether Rituximab (anti-CD20) treatment could interfere with B-CLL detection levels in our Labcorp CLL ERIC MRD assay.