Tisagenlecleucel Outcomes in Relapsed/Refractory Extramedullary ALL: A Pediatric Real World CAR Consortium Report.

Chimeric antigen receptor (CAR) T-cells have transformed the therapeutic options for relapsed/refractory (R/R) B-cell ALL. Data for CAR therapy in extramedullary (EM) involvement is limited. Retrospective data was abstracted from the Pediatric Real World CAR Consortium (PRWCC) of 184 infused patients from 15 US institutions. Response (CR) rate, overall survival (OS), relapse-free survival (RFS), and duration of B-cell aplasia (BCA) in patients referred for tisagenlecleucel with EM disease (both CNS3 and non-CNS EM) were compared to bone marrow (BM) only. Patients with CNS disease were further stratified for comparison. Outcomes are reported on 55 patients with EM disease prior to CAR (n=40 CNS3; n=15 non-CNS EM). The median age at infusion in CNS cohort was 10 years (range <1-25) and the non-CNS EM cohort was 13 years (2-26). In patients with CNS disease, 88% (35/40) achieved a CR, versus only 66% (10/15) with non-CNS EM disease. Patients with CNS disease (both with and without marrow involvement) had comparable 24-month OS outcomes to non-CNS EM or BM only (p=0.41). There was no difference in 12-month RFS between CNS, non-CNS EM, or BM only patients (p=0.92). No increased toxicity was seen with CNS or non-CNS EM disease (p=0.3). Active CNS disease at time of infusion did not impact outcomes. Isolated (iCNS) disease trended towards improved OS when compared to combined CNS and BM (p=0.12). R/R EM disease can be effectively treated with tisagenlecleucel with toxicity, relapse rates and survival rates comparable to patients with BM only. Outcomes for iCNS relapse are encouraging.