Post-CAR-T Minimal Residual Disease (MRD) Monitoring in Mantle Cell Lymphoma Enables Early Relapse Detection

Abstract

INTRODUCTION: Over 40% of patients with mantle cell lymphoma (MCL) will progress within 1 year after treatment with brexucabtagene autoleucel (Brexu-cel)(Michael Wang et al. ZUMA-2 NEJM 2020). Monitoring minimal residual disease (MRD) of circulating tumor cells (CTC) via next-generation sequencing of the immunoglobulin sequences (IgHTS) with a sensitivity of 1 in million (ClonoSeq, Adaptive Biotechnologies) has previously been shown to identify patients at high risk of MCL relapse (Simone Ferrero et al. Blood 2022). However, there is a limited understanding of MRD monitoring after Brexu-cel. A sub-analysis of 27 patients post-Brexu-cel in ZUMA-2 showed predictive performance of MRD measured at months 1, 3, and 6 in estimating relapse potential. METHODS: Clonotypes were identified from paraffin-embedded tissues and underwent PCR amplification of the IgH, IgH-DJ, and Ig Kappa/lambda regions. CTC MRD assessments were monitored at 1, 3, 6, and 12 months (if applicable) following standard-of-care brexu-cel infusion in all patients with MCL at our center who had at least 3 months of follow-up. PFS and overall survival (OS) were determined by Kaplan-Meier analysis and significance by log-rank test. The comparison between the two groups was conducted using a two-tailed Mann-Whitney test. Significances were calculated using a Fisher exact test between two categorical variables or as otherwise specified. Statistical analysis and plots were generated using Prism 8.4.1 (GraphPad) RESULTS: Between January 2020 and December 2022, all treated patients (n=34) were analyzed. 3 patients were excluded as they were unable to reach day 28 (D28) assessments due to death, progressive disease, or refusal of CAR-T infusion. 5 patients were excluded due to a follow-up of <3 months. The median follow-up time for the 26 included patients was 18.9 months. The median age was 68, 73% were male and 27% were female, 4 median lines of therapy prior, including AutoHSCT (34.6%) or BTKi (92%). The best overall response rate at D28 was 100% with a CR rate of 73% which was similar to ZUMA-2. The median OS was 18.9 months and the median PFS was 15.3 months. We chose to analyze the Day 28 MRD assessment and found 17 of 23 patients (74%) had undetectable MRD and 6 patients had detectable MRD (26%). Due to the relatively small sample size, no significant differences were found between Age, Gender, Pre-treatment LDH, MIPI score, Ki-67, TP53 mutational status, and probability of Day 28 undetectable MRD. Notably, however, 3 of the 6 patients with TP53 mutations had detectable Day 28 MRD. Those patients with detectable MRD compared with those with undetectable MRD had a lower median PFS of 10.74 months vs 17.69 months (p-value= 0.21, Figure 1); although the median OS was similar of 17.69 and 17.84 months, (p-value= 0.75) respectively. 88% of patients (15 out of 17) with undetectable MRD on Day 28 not only maintained this status at 6 months but also showed no radiological disease progression in 93% (14 out of 15) of cases at the time of longest follow-up. A total of 7 patients relapsed during follow-up. MRD predicted 6 impending relapses earlier than PET CT with a median of 294 days (range 15-332 days) prior to progression (Figure 2). CONCLUSION: Evidence from the ZUMA-2 study and our study highlights the significance of early post-CAR-T MRD as an independent prognostic marker for predicting disease recurrence and durable remissions in MCL. Combining MRD measurements with PET-CT at months 1, 3, and 6 after CAR-T therapy can effectively identify high-risk patients for disease progression, offering promising potential to improve outcomes in MCL.