Baseline platelet-to-lymphocyte ratio is associated with severe immune effector cell-associated toxicities in diffuse large B-cell lymphoma patients receiving anti-CD19 CAR T-cell therapy.

Introduction: Anti-CD19 chimeric antigen receptor (CAR) T-cell therapy can induce durable remissions in patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL); however, severe immune effector cell-associated adverse events, including cytokine release syndrome (CRS) and neurotoxicity, remain major clinical challenges. We investigated whether the platelet-to-lymphocyte ratio (PLR) could serve as a predictive biomarker for severe toxicities. Methods: In this retrospective study, 15 patients with relapsed or refractory DLBCL treated with tisagenlecleucel were analyzed. PLR was measured prior to lymphodepletion. Receiver operating characteristic (ROC) analysis was performed to determine the optimal PLR cutoff for predicting severe immune-related adverse events. Results: The optimal PLR cutoff was 198, with a sensitivity of 85.7% and a specificity of 87.5%. Patients with higher baseline PLR values had a significantly higher incidence of severe adverse events compared with those with lower PLR values (85.7% vs. 12.5%). Baseline PLR was positively correlated with post-infusion increases in serum ferritin, a surrogate marker of systemic inflammation. Compared with other inflammatory biomarkers, PLR demonstrated an intermediate sensitivity-specificity trade-off. Conclusion: Baseline PLR may represent a simple and accessible biomarker associated with an increased risk of severe immune-related toxicities following CAR T-cell therapy. These findings support its potential role in pre-infusion risk stratification, although validation in larger cohorts is warranted.