Population-Based External Validation of the EASIX Scores to Predict CAR T-Cell-Related Toxicities

SIMPLE SUMMARY: CAR T-cell therapy became standard of care for patients with relapsed or refractory large B-cell lymphoma. However, their administration can be accompanied by toxicities, such as cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome. It is important to identify patients at risk for these toxicities in order to start an early intervention in high-risk patients and guide outpatient CAR T-cell treatment. As a consequence, several easy-to-use risk scores including the EASIX and its derivatives were developed. However, in the available studies, disparities existed among the used endpoints and cutoff values, hampering the utility of these tools in practice. This study aims to validate these EASIX scores in a population-based cohort. This can be used to select the best predictive model and to further guide optimization of the proposed risk scores. ABSTRACT: Cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) can hamper the clinical benefit of CAR T-cell therapy in patients with relapsed/refractory large B-cell lymphoma (r/r LBCL). To assess the risk of CRS and ICANS, the endothelial activation and stress index (EASIX), the modified EASIX (m-EASIX), simplified EASIX (s-EASIX), and EASIX with CRP/ferritin (EASIX-F(C)) were proposed. This study validates these scores in a consecutive population-based cohort. Patients with r/r LBCL treated with axicabtagene ciloleucel were included (n = 154). EASIX scores were calculated at baseline, before lymphodepletion (pre-LD) and at CAR T-cell infusion. The EASIX and the s-EASIX at pre-LD were significantly associated with ICANS grade ≥ 2 (both p = 0.04), and the EASIX approached statistical significance at infusion (p = 0.05). However, the predictive performance was moderate, with area under the curves of 0.61–0.62. Validation of the EASIX-FC revealed that patients in the intermediate risk group had an increased risk of ICANS grade ≥ 2 compared to low-risk patients. No significant associations between EASIX scores and CRS/ICANS grade ≥ 3 were found. The (m-/s-) EASIX can be used to assess the risk of ICANS grade ≥ 2 in patients treated with CAR T-cell therapy. However, due to the moderate performance of the scores, further optimization needs to be performed before broad implementation as a clinical tool, directing early intervention and guiding outpatient CAR T-cell treatment.