The Dynamic Role of Liquid Biopsy in Patients with Non-Small Cell Lung Cancer Receiving Immune Checkpoint Inhibitors: Emerging Opportunities and Clinical Challenges

Immune checkpoint inhibitors (ICIs) have transformed the treatment of non-small-cell lung cancer (NSCLC), yet predicting durable benefit and detecting resistance remain major challenges. As immunotherapy expands across disease stages, minimally invasive tools are increasingly needed to monitor response and inform treatment personalization. Liquid biopsy enables serial assessment of circulating tumor DNA (ctDNA) and other blood-based biomarkers, complementing tissue analysis and imaging. This review critically synthesizes evidence across resectable, locally advanced, and metastatic NSCLC, integrating ctDNA dynamics with emerging multi-omics approaches. Its contribution is to distinguish the prognostic value of circulating biomarkers from evidence that using them to guide treatment improves patient outcomes, while identifying priorities for clinical translation. Across the reviewed studies, ctDNA clearance is associated with favorable outcomes, whereas persistent or rising ctDNA signals an increased risk of recurrence or progression, sometimes before radiological detection. Methylation, fragmentomics, plasma proteomics, and immune-cell profiling may provide complementary information on tumor-immune interactions. However, low tumor shedding, clonal hematopoiesis, assay variability, and unvalidated intervention thresholds limit routine use. The expansion of perioperative immunotherapy and emerging interest in biomarker-guided treatment adaptation make this synthesis timely. Prospective interventional trials are needed to determine whether liquid biopsy can safely guide treatment escalation, de-escalation, or discontinuation. By clarifying both the promise and the limitations of longitudinal monitoring, this review informs research aimed at detecting ineffective treatment earlier and reducing unnecessary treatment exposure while preserving cancer control.