The Role of Biomarkers in Personalized Treatment of Gastrointestinal Cancers.

Gastrointestinal (GI) cancers-including colorectal, gastric, pancreatic, and esophageal malignancies- remain among the most prevalent and lethal cancers worldwide, largely due to their biological complexity and late-stage diagnosis. This narrative review examines the critical role of biomarkers in advancing personalized treatment strategies for GI cancers. Key diagnostic, prognostic, and predictive biomarkers, such as KRAS, HER2, PD-L1, microsatellite instability (MSI), and circulating tumor DNA (ctDNA), are discussed about their application in clinical decision-making. The review highlights biomarker-driven approaches across different GI cancer types, demonstrating how molecular profiling informs early detection, treatment selection, and monitoring of therapeutic response. Recent technological advances-including liquid biopsy, next-generation sequencing, and multi-omics integration- have expanded biomarker discovery and enhanced clinical utility. Challenges in implementing biomarker testing, such as variability in expression, lack of standardization, and limited accessibility, are also addressed. Overall, this article emphasizes the transformative potential of biomarkers to tailor therapy, improve patient outcomes, and shape the future of precision oncology in gastrointestinal cancers.