A Real-World Comparison of CAR T-Cell Therapy Versus a Historical Standard-of-Care Approach for Relapsed-Refractory Large B-Cell Lymphoma in Ontario, Canada

Background

Anti-CD19 Chimeric Antigen Receptor T-cell (CAR-T) immunotherapies have been funded in Canada for patients with relapsed-refractory large B-cell lymphoma (RR LBCL) after two lines of systemic therapy since December 2019. However, real-world evidence of CAR-T outcomes has been limited to small series with little comparison to prior standard-of-care management. We compared overall survival (OS), adverse events, and healthcare utilization for a cohort of patients with RR LBCL consecutively treated with CAR-T versus a cohort of historical controls treated with standard-of-care therapy prior to CAR-T approval.

Methods

This is a propensity-weighted retrospective cohort study of patients with RR LBCL treated at Princess Margaret (PM) Cancer Centre. Using linked clinical and administrative datasets, consecutive patients treated with CAR-T (2020-2022) following provincial funding approval were compared to a matched cohort of historical controls (2012-2017). Patients were followed from index date, defined as the date of progression following 2 lines of chemotherapy (2L) in the historical controls and following last therapy (2L or higher) in the CAR-T patients for up to 3-years, with maximum follow-up to March 31, 2023. Stabilized inverse probability treatment weighting (sIPTW) was used to account for confounding between cohorts (age, sex, lactate dehydrogenase, and comorbidities). Kaplan meier curves and IPTW-weighted Cox proportional hazard regression analyses estimated the adjusted hazard ratio (HR) between treatment cohort and OS. A landmark survival analysis of patients alive at 3 months post-index date addressed immortal time bias. Adverse events (AEs) from inpatient/emergency department [ED] diagnoses and healthcare utilization were reported per 1000 person-days at risk.

Results

A total of 86 CAR-T patients and 150 historical control patients were evaluable for comparison. Variables were balanced after applying the sIPTW (based on standardized difference <0.1); mean age was 56 years and males comprised 61%. Prior treatment included ASCT in 27.6% CAR-T vs 38.4% historical control patients (standardized difference 0.21; p=0.09). Post-2L progression, 58% of historical controls had no further treatment, 32% received intravenous or oral chemotherapy/targeted agents, 6.2% had an autologous stem cell transplant, and 10% received palliative chemotherapy and/or radiotherapy. CAR-T patients received tisagenlecleucel (33.3%) and axicabtagene ciloleucel (66.7%) CAR-T products. The OS probabilities at 1-, 2-, and 3-years were 68% (95% CI 53-79%), 60% (95% CI 44-73%), and 57% (95% CI 39-71%), respectively, in the CAR-T group, and 18% (95% CI 12-25%), 11% (95% CI 7-17%), and 10% (95% CI 5-16%), respectively, in the control group. The IPTW-adjusted HR for all-cause death was 0.22 (95% CI 0.15-0.33), and landmark survival analysis for all-cause death 3-months post-index date to end of follow-up generated a similar HR of 0.28 (CI 0.19-0.44) in the CAR-T group.

CAR-T patients had a lower number of days hospitalized (77.73 [95% CI 75.00-80.57] vs 86.11 [95% CI 83.12-89.21] per 1000 person-day; p<0.001), ICU admissions (0.55 [95% CI 0.36-0.84] vs 1.26 [95% CI 0.94-1.69] per 1000 person-day; p=0.001), and ED visits (4.79 [95% CI 4.10-5.61] vs 2.07 [95% CI 1.65-2.60] per 1000 person-day; p<0.001). Additionally, CAR-T patients had lower events per 1000 person-days of: infection (1.44 [95% CI 1.10-1.87] vs 3.02 [95% CI 2.50-3.64] p<0.001), neutropenia (0.65 [95% CI 0.44-0.96] vs 1.79 [95% CI 1.4-2.29]; p<0.001), febrile neutropenia (0.45 [95% CI0.28-0.72] vs 1.47 [95% CI 1.12-1.92]; p<0.001), gastrointestinal toxicity (0.26 [95% CI 0.14-0.49] vs 0.69 [95% CI 0.46-1.02]), and respiratory infections (0.51 [95% CI 0.33-0.79] vs 0.91 [95% CI 0.65-1.29]; p=0.04).

Conclusions

CAR T-cell therapy produced a significant and sustained survival benefit versus historical standard-of-care management, with fewer hospitalizations and infections. Despite well-described CAR-T toxicities, historical control patients had more AEs, underscoring the lack of other effective salvage treatments. This study describes one of the largest real-world comparisons of patients with RR LBCL receiving CAR T-cell therapy compared to previous standard-of-care therapies and demonstrates its effectiveness amongst a broad cohort of eligible patients, consistent with the results of pivotal trials.