Decoding Brain Metastasis With Liquid Biopsy: Biomarkers and Technologies in <scp> <i>EGFR</i> </scp> ‐Mutant <scp>NSCLC</scp>

Brain metastasis (BM) is a leading cause of cancer-related mortality, particularly in patients with lung cancer. Traditional diagnostic methods, such as tissue biopsies, are often impractical, and there are currently no reliable biomarkers for early detection in clinical practice. In this context, liquid biopsy has emerged as a valuable non-invasive diagnostic tool for cancer patients with BM. This review summarizes the advantages and current limitations (such as the low sensitivity in early-stage disease and the potential for false positives from non-cancer sources) of liquid biopsy samples, specifically focusing on peripheral blood and cerebrospinal fluid (CSF). We discuss key biomarkers, including circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), extracellular vesicles (EVs), and tumor-derived platelets (TEPs), and current technologies for their detection, highlighting their potential clinical applications. Additionally, we explore the role of liquid biopsy in patients with epidermal growth factor receptor-mutated (EGFR-mutant) non-small cell lung cancer (NSCLC), a group that experiences a high incidence of BM. Finally, we address emerging biomarkers and innovative detection methods, offering recommendations for enhancing the application of liquid biopsy in clinical settings. Our review aims to underscore the significance of liquid biopsy in improving the detection and management of BM.