Role of Liquid Biopsy in Cancer Diagnosis: A Comparative Evaluation with Conventional Techniques

Abstract

Tissue biopsy and histopathological evaluation-considered the gold standard-are traditionally used for cancer diagnosis; however, these procedures are invasive and limited in their ability to accurately capture tumor heterogeneity. Liquid biopsy has emerged as a minimally invasive alternative that enables molecular characterization through circulating tumor- derived biomarkers. This review critically evaluates the biological basis, technical platforms, and clinical applications of liquid biopsies, including circulating tumor DNA (ctDNA), Circulating Tumor Cells (CTCs), exosomes, and other circulating biomarkers. A comparative analysis with conventional tissue biopsies was conducted based on invasiveness, diagnostic accuracy, assessment of tumor heterogeneity, capacity for timely monitoring, cost-effectiveness, and clinical utility. Liquid biopsy offers significant advantages regarding minimal invasiveness, repeatability, and the dynamic monitoring of tumor progression and treatment response. It holds potential for detecting minimal residual disease and emerging resistance mutations. However, challenges remain concerning analytical sensitivity, test standardization, cost, and regulatory implementation in early-stage cancer. Tissue biopsy continues to provide essential morphological, histological, and staging information. Current evidence indicates that liquid biopsy is a complement to, rather than a substitute for, traditional tissue-based diagnosis. Integrating molecular profiling with conventional histopathology can advance the precision oncology approach. 'Liquid biopsy' represents a revolutionary advancement in cancer testing. While it holds great promise for real-time disease monitoring and personalized therapy, its optimal clinical role lies in complementing existing diagnostic techniques rather than completely replacing them.