Liquid biopsy-based T-cell receptor profiling in lung cancer patients undergoing immunotherapy

Abstract

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer, and immune checkpoint inhibitors targeting the PD-1/PD-L1 pathway have significantly improved patient outcomes. However, only a subset of patients respond to treatment, highlighting the need for predictive biomarkers. The T-cell receptor (TCR) repertoire reflects the adaptive immune response and has emerged as a promising candidate biomarker for immunotherapy response. The aim of this study was to investigate whether the characteristics of the peripheral blood TCR repertoire are associated with response to anti-PD-1/PD-L1 therapy in NSCLC patients. A total of 96 longitudinal blood samples from n=18 NSCLC patients undergoing anti-PD-1/PD-L1 treatment were analysed using TCR-beta sequencing with the SiMSen-seq method. Following quality control and bioinformatic processing with a molecular identifier groups-based error correction (MIGEC) pipeline, repertoire diversity was evaluated using the number of unique clonotypes, the D50 index, and the Shannon diversity index. In addition, clonal expansion patterns were assessed by tracking highly variable clonotypes over time. Responders consistently exhibited higher TCR repertoire diversity than non-responders. At the pre-treatment baseline, responders showed a 55% higher median number of unique clonotypes, as well as higher median D50 and Shannon index values. Across all time points, responders maintained a more diverse repertoire, with a 33% higher median number of clonotypes, an 8 percentage points higher D50 index, and a 9% higher Shannon index compared with non-responders. Analysis of individual clonotype expansion revealed highly heterogeneous patterns and no clear distinction between responders and non-responders. These findings suggest that overall TCR repertoire diversity is associated with improved response to anti-PD-1/PD-L1 therapy in NSCLC, whereas monitoring individual clonotypes alone appears to be insufficient as a predictive biomarker. Larger studies are required to validate these observations and assess the clinical utility of TCR repertoire profiling in immunotherapy response prediction. Keywords: Non-small cell lung cancer, T-cell receptor repertoire, TCR-beta