Peripheral Blood ETASTs for Predicting Efficacy of Chemoimmunotherapy in NSCLC

Non-small cell lung cancer (NSCLC) accounts for the majority of lung cancer cases globally. While immune checkpoint inhibitors (ICIs), particularly PD-1/PD-L1 inhibitors combined with platinum-based chemotherapy, have become standard first-line therapy for advanced NSCLC, only a subset of patients achieve clinical benefit. Current biomarkers including PD-L1 expression and tumor mutational burden (TMB) have limited predictive accuracy, creating an urgent need for more reliable biomarkers. Tumor antigen-specific T cells (TASTs) are the actual effectors in ICI therapy, and successful ICI response depends on reactivation of these cells. However, detection of circulating tumor antigen-specific T cells (CTASTs) has been technically challenging due to their low frequency and heterogeneity in peripheral blood. This study utilizes a novel Circulating Tumor-Specific T Cell Nanodetection Technology (CTT-NanoDT) developed by the research team. The technology employs Tumor Antigen-specific T cell Activating Nanoparticles (TATAN) loaded with whole tumor cell components to specifically activate and quantify effector TASTs (ETASTs) in peripheral blood. Study Design: This is a prospective, single-center, observational cohort study enrolling 80 patients with stage IIIB-IV NSCLC receiving standard PD-1 inhibitor plus platinum-based chemotherapy. Peripheral blood samples (5 mL) will be collected at two time points: baseline (T0, within 1 day before treatment initiation) and after completion of cycle 2 (T1, day 21 of cycle 2). ETAST Detection Protocol: 1. PBMC isolation from peripheral blood using Ficoll density gradient centrifugation 2. Co-incubation of PBMCs with TATAN nanoparticles (50 μg/mL) for 48 hours at 37°C 3. Flow cytometric quantification of activated ETASTs defined as CD3+CD8+IFN-γ+ and CD3+CD8+CD137+ double-positive cells 4. Calculation of ΔETAST: \[(ETASTs-T1 - ETASTs-T0) / ETASTs-T0\] × 100% Primary Endpoint: Progression-free survival (PFS), defined as time from treatment initiation to first documented disease progression per RECIST 1.1 or death from any cause, assessed by independent radiology committee. Secondary Endpoints: 1. Comparison of predictive performance (ROC curve AUC) between ΔETASTs and traditional biomarkers (PD-L1 TPS, TMB) using DeLong test 2. Objective response rate (ORR), overall survival (OS), disease control rate (DCR) 3. Treatment-related adverse events graded per CTCAE 5.0 Statistical Analysis: Cox proportional hazards regression will assess the association between ΔETASTs and PFS. Patients will be stratified by median ΔETAST value into high and low change groups for survival comparisons using Kaplan-Meier curves and log-rank tests. Sample size of 80 provides 80% power to detect HR=0.42 with α=0.05, accounting for 15% dropout rate. The study aims to establish ΔETASTs as a superior biomarker for predicting chemoimmunotherapy efficacy in NSCLC, potentially enabling precision patient selection and improving treatment outcomes.