Personalized Monitoring of Circulating Tumor DNA By a Specific Signature of Trackable Mutations after Chimeric Antigen Receptor t-Cell Therapy in Non-Hodgkin B Cell Lymphoma

Introduction: CAR-T therapy has produced a paradigm shift for the treatment of non-Hodgkin B-cell lymphomas (NHBcL). Strategies to optimize the disease surveillance after this therapy are increasingly necessary. This study aims to explore the potential value of a circulating tumor DNA (ctDNA) monitoring with an innovative signature of personalized trackable mutations. Methods: Twenty-five NHBcL treated with CD19 CAR-T cell therapy were included in 2 academic hospitals (10 follicular lymphoma-FL and 15 large B-cell-LBCL). Clinical outcomes are shown in Table 1. Genomic profiling was performed in relapse FFPE biopsy to detect somatic mutations by a custom capture enrichment panel (Twist, USA) of 134 genes (NextSeq, Illumina) suitable for liquid biopsy MRD monitoring (LiqBio-MRD) (Jiménez Ubieto 2023). A total of 93 peripheral blood samples were collected to isolate plasma at day +7, +14, +30, +90 and before progression (45 LBCL and 48 FL). The potential VAF sensibility of the test was below 10−4. PET/CT examinations were performed on day +90, +180, +365 and every 6 months in FL, and the same but also adding day +30 for LBCL. Results: We found 136 trackable mutations suitable for MRD monitoring in all the patients (mean of 5.44 per patient). The most frequently mutated genes were CREBBP (80%), KMT2D (50%) and EP300 (30%) in FL and CREBBP (43.7%), KMT2D (37.5%), TP53 (37.5%) and TNFRSF14 (31.2%) in LBCL. The dynamics of the baseline mutations in the 25 patients were shown in Figure 1. Among the 15 patients who progressed, 11 presented LiqBio-MRD + result (ctDNA) in all samples before progression. Regarding the remaining: DLCBL2 had a single in relapse; DLCBL7 had two negative MRD samples and subsequently a LiqBio-MRD + sample before progression; and FL107 had one negative MRD sample and subsequently a LiqBio-MRD + sample before progression. All LBCL patients who didn’t progress achieved persistent MRD—status since month one. However, 4 out of 6 FL patients who had MRD + status at month one became negative in the following samples and didn’t progress. As shown in Figure 2, ctDNA surveillance exhibited high agreement with the PET-CT results. Remarkably, 33/36 negative PET-CTs (91.7%) were consistent with a LiqBio-MRD—determination, and 11/13 positive PET-CTs (85%) were LiqBio-MRD +. Patients with PET-CT positive but LiqBio-MRD—(n = 2) resulted as false positive PET/CT (cervical mass confirmed by biopsy and mesenteric mass becoming negative in the next PET/CT analysis). Furthermore, patients with PET-CT negative and LiqBio-MRD + (n = 3) presented progression. Conclusions: In the case of FL undergoing CAR T-cell, this is the first in FL study demonstrating the utility of a non-invasive personalized MRD evaluation in liquid biopsy. Our LiqBio-MRD test is able to predict LBCL and FL outcome and could be of high utility to detect false positives or negatives PET/CT assessments during follow-up. Keywords: Cellular therapies, Liquid biopsy, Minimal residual disease No conflicts of interests pertinent to the abstract.