Beyond Detection: Conventional and Emerging Biomarkers in Gastrointestinal Cancers

Gastrointestinal (GI) cancers, particularly colorectal and gastric cancers, majorly contribute to global cancer mortality due to frequent late-stage diagnosis and poor therapeutic response in advanced disease. Earlier detection of GI cancers is needed for a better prognosis. This review examines both traditional and emerging biomarkers that contribute significantly to early detection, prognostication, and prediction of therapeutic resistance or sensitivity. Specifically, we highlight the diagnostic utility of non-invasive liquid biopsy biomarkers such as circulating tumor DNA (ctDNA), microRNAs (miRNAs), and exosomes. Moreover, we discuss the prognostic and predictive value of conventional genetic alterations, including KRAS, BRAF, and HER2. Although new findings have shown the advantages of liquid biopsy over colonoscopy, there are still limitations to the technique, such as cost-effectiveness, technological gaps in low-resource settings, and uncertain detection rates. Further studies are required to test the validity and accessibility of liquid biopsy and its biomarkers in order to advance personalized diagnosis and treatments for GI cancers. Such a study will be helpful for clinicians to better manage patients with GI cancers.