CD20 and CD19 expression loss in relapsed or refractory b-cell non-Hodgkin lymphoma: A retrospective cohort.

Abstract

e19537 Background: CD20-targeted therapies such as rituximab are widely used in the management of B-cell non-Hodgkin lymphoma (NHL). Re-treatment with anti-CD20 agents is common, however previous research has demonstrated loss of CD20 expression at time of relapse or refractory disease in a subset of patients. There is also amplified interest in alternative targets, specifically CD19, in the relapsed or refractory setting. Incidence of CD19 loss has been explored in post-CAR T cell therapy patients but not described elsewhere. We hypothesized that CD marker loss may be higher than previous reports due to expanded use of CD20- and CD19-targeted therapy. Methods: The present study is a retrospective cohort analysis of 229 patients with B-cell NHL from Harbor-UCLA Medical Center in Los Angeles, CA from 2006 to 2022. Charts were retrospectively reviewed for cases of B-cell NHL, and data was collected about demographics, diagnosis, treatment, and relapses. CD20 and CD19 expression analysis was performed by immunohistochemistry and / or flow cytometry at diagnosis and at each relapse whenever possible. The primary endpoint of the study was the rate of CD marker expression loss at time of relapse. Results: The cohort of 229 patients was composed of 54.1% diffuse large B-cell lymphoma (DLBCL), 14.4% follicular lymphoma (FL), 8.3% high-grade B-cell lymphoma (HGBCL), 7.0% marginal zone lymphoma (MZL), 4.8% mantle cell lymphoma (MCL), and 11.2% other. Overall, 28.8% (66/229) patients had relapsed or refractory disease. The rate of CD20 expression loss was 7.9% (5/63) across all relapses with two patients converting at first relapse (1 FL relapsing as HGBCL, 1 MZL), two patients at 2nd relapse (1 FL relapsing as DLBCL, 1 MZL relapsing as DLBCL), and one patient at 5th relapse (1 MZL). All five patients with CD20 phenotypic conversion received rituximab, and three patients received two or more rounds of anti-CD20 therapy. The median OS after CD20 expression loss was 4 months (95% CI 3.3 – 4.7 months). All patients (14/14) who had CD19 testing performed at relapse maintained CD19 positivity. Conclusions: This retrospective study demonstrates a rate of CD20 expression loss at relapse of 7.9%, which is less than previously reported rates ranging between 11-60%. CD20 expression loss seems to be associated with transformation to high-grade lymphoma, poor overall survival, and marginal zone histology. The conservation of CD19 expression across relapses supports the use of novel anti-CD19 targeted therapy in the relapsed or refractory setting. Whenever possible, repeat biopsy should be done at time of relapse prior to treatment with CD-targeted therapy. This study is of notable clinical relevance with expanded use of anti-CD20 agents and novel CD19-targeted therapies in the management of B-cell NHL.