Liquid biopsy for the diagnosis, prognosis, and monitoring of common cancers: global and Brazilian perspectives

Abstract Cancer is among the most prevalent diseases worldwide and a leading cause of death. Although histopathological analysis of tumor tissue obtained through biopsy remains the gold standard for diagnosis, liquid biopsy (LB) has emerged as a minimally invasive and promising alternative, enabling the detection and analysis of tumor-derived biomarkers in body fluids. This study focuses on the five most common global cancers: lung, breast, colorectal, prostate, and gastric cancers. Blood, plasma, and serum are the primary fluids analyzed, with biomarkers such as exosomes, microRNAs, circulating tumor cells (CTCs), and circulating tumor DNAs (ctDNAs) under investigation. Among these biomarkers, ctDNAs and CTCs show the greatest clinical relevance. LB offers applications in diagnosis, prognosis, treatment monitoring, and detection of minimal residual disease. A global trend toward multimodal LB approaches, integrating genetic and epigenetic biomarkers, is accelerating clinical transition. Several Food and Drug Administration (FDA)-approved LB tests are already used clinically. PCR-based tests such as Cobas and Idylla™ detect EGFR mutations in cancers such as lung adenocarcinoma. Next-generation sequencing-based platforms such as Guardant360 and FoundationOne Liquid analyze over 70 genes across diverse tumors. In Brazil, despite promising results, the only LB method routinely used is the CellSearch system, limited to metastatic breast, prostate, and colorectal cancers. The application of the LB in public healthcare is constrained by high costs and limited infrastructure. Expanding LB use in Brazil will require investment, cost reduction strategies, and locally validated clinical studies. Globally, further research is essential to fully incorporate LB into clinical oncology and make it accessible to broader patient populations.