Publication

Abstract : Context Chimeric antigen receptor T-cell (CAR-T) therapy has emerged as novel therapeutic agent for the treatment of relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL). The landscape of dysfunctional immune mechanism in peripheral blood mononuclear cells (PMBCs) post CAR-T remains largely unclear. Knowledge regarding kinetics of CAR-T cells postinfusion is limited, and whether these features might have any predictive value in the long term has not been clearly elucidated. Study Setting We studied detailed features of the CAR-T-cell product as well as CAR-T expansion and persistence after infusion using lymphocyte count, morphological evaluation, and multiparametric flow cytometry (MFC) in a total of 6 R/R DLBCL patients receiving CAR-T at our center over a period of 6 months (July 2023–January 2024). Intervention All patients received CAR-T therapy post fludarabine–cyclophosphamide conditioning as per protocol. Flow cytometric immunophenotyping was done at baseline, and at days 7, 30, and 60 postinfusion. Results Lymphocytes showed a progressive increase from 0% to 2% at day 1 to a peak of 40%-75% on day 7-10. Peripheral smear (PS) examination in all cases revealed abnormal lymphoid cells from blastoid to large, atypical forms by the end of the first week. MFC showed median percentage of various lymphocyte subsets on day 7 as follows: CD3 (90.88%; range, 69.00%-99.81%), CD4 (35.39%; range, 9.09%-69.85%), CD8 (46.51%; range, 17.09%-76.61%), CD19 (0.00%; range, 0.00%-0.32%), and NK cells (10.81%; range, 4.51%-29.00%). At the time of peak expansion, there was predominance of CD8+ T cells with a reduction in the ratio of CD4/CD8 across all cases. All cases were associated with persistence of complete B-cell aplasia (BCA) on day 60 except 1 patient not achieving clinical remission. Conclusion A meticulous assessment of lymphocyte trend analysis, PS, and bone marrow specimen may thus be used as a simple, costeffective monitoring tool for proliferation and expansion of CAR-T cells. MFC gives supportive evidence of CAR-T-cell expansion in the form of predominance of T lymphocytes, reduced CD4/CD8 ratio, and relative BCA. Furthermore, persistence of BCA can be explored as predictor of remission status in a larger prospective study.