Real-world duration of hospitalization for CAR-T treatment: US patient experience in multiple hematologic malignancies.

e18896 Background: Since 2017, 6 CAR-t therapies have been approved to treat pediatric and adult hematologic malignancies (HM). Due to the complexity of administration and severe toxicity including cytokine release syndrome (CRS), CAR-t is usually administered in an inpatient setting. We sought to provide the first pan-cancer, U.S. based analysis of duration of hospitalization during CAR-t overall and for patients who experience CRS. Methods: Patients were identified from a large, US based EMR database including more >40M patients, >500 hospitals and 30 healthcare systems including both community/academic health systems. Patients with ≥1 procedure code for general administration of CAR-t therapy (e.g.: XW033C3, introduction of engineered autologous chimeric antigen receptor t-cell immunotherapy into peripheral vein) or a specific approved CAR-T (XW033K7, introduction of idecabtagene vicleucel immunotherapy into peripheral vein) between 2017 and 2022 and a diagnosis of a HM were selected. CRS was identified as the presence of any ICD-10 diagnosis code of D89.83X post-administration. Time from the date of CAR-t administration to hospital discharge was calculated overall, by cancer type, and for patients with and without a confirmed diagnosis of CRS. Results: A total of 212 patients (multiple myeloma [MM] = 64, b-cell lymphoma = 77, follicular lymphoma = 47, mantle cell lymphoma [MCL] = 13, acute lymphoblastic leukemia = 11) meeting selection criteria were identified. Cohort characteristics are shown in Table 1. Median duration of hospitalization was 12 days (range 1-56); shortest at 10 days for MM and longest at 15 days for MCL. Mean duration of hospitalization decreased slightly from 12.3 days (sd = 11) for patients treated in 2019 or earlier to 11.9 days (sd = 4.2) for patients treated in 2022 Median duration of hospitalization for patients with a CRS diagnosis (n = 100) was 12 (range 1-30) versus 11 days (range 1-56) for those without CRS (n = 112). Conclusions: CAR-t poses a unique set of administrative, logistical and clinical challenges. This study provides the first contemporaneous estimates of the length of hospital stays during CAR-t infusion which was found to be 12 days. Differences in length of hospitalizations did not decline significantly over time or were significantly different between those with and without CRS however further research to examine health system factors and patient factors (i.e., severity of CRS) are needed. [Table: see text]