INTRODUCTION: Current guidelines do not mandate CD19 tumor expression assessment before chimeric antigen receptor T-cell (CAR-T) therapy in large B-cell lymphoma (LBCL) patients due to limitations of immunohistochemistry (IHC) or flow cytometry. Quantitative polymerase chain reaction (qPCR) offers a more sensitive alternative for detecting CD19 expression, with the primary advantage that mRNA can be easily extracted from paraffin-embedded tissues.

METHODS & RESULTS: In our study, we included 51 adult patients with LBCL treated with axicabtagene ciloleucel. Among them, 16 were classified as CD19-negative by IHC; however, qPCR reclassified six (37.5%) as CD19-positive. We then compared the outcomes between consistently CD19-negative (IHC^-qPCR^-) and CD19-positive (IHC⁺ and IHC^-qPCR⁺) patients. CD19-negative cohort showed worse 1-year progression-free survival (15 vs. 45%, p = 0.044) and a trend toward shorter duration of response (29 vs. 55%, p = 0.065). Only one (10%) of the CD19-negative patients remained alive and disease-free at last follow-up (6 months), having previously responded to bridge therapy.

DISCUSSION: If confirmed in a large patient cohort, these findings could form the basis for modifying current patient selection criteria. Consistently negative patients may be suboptimal candidates for anti-CD19 CAR-T therapy. Alternative therapeutic options, such as bispecific antibodies or polatuzumab-based regimens, could be considered for this subset of patients.