The Genetic Landscape of Colorectal Cancer: From Molecular Alterations to Therapeutic Decision Pathways

Colorectal cancer (CRC) remains one of the leading causes of cancer-related morbidity and mortality worldwide despite substantial advances in screening, surgical techniques, systemic therapies, and multidisciplinary care. The increasing implementation of precision oncology has fundamentally transformed CRC management by enabling molecularly guided therapeutic strategies based on tumor-specific genetic alterations. In recent years, the molecular landscape of CRC has expanded considerably beyond traditional histopathological classification, incorporating a growing number of clinically actionable biomarkers with prognostic, predictive, and therapeutic significance. This review provides a comprehensive and up-to-date overview of the genetic landscape of CRC, focusing on established biomarkers currently integrated into clinical practice, including microsatellite instability/mismatch repair deficiency (MSI/dMMR), KRAS, NRAS, BRAF, HER2, and NTRK alterations. In addition, emerging biomarkers such as tumor mutational burden (TMB), POLE/POLD1 mutations, circulating tumor DNA (ctDNA), DNA damage repair (DDR) alterations, transcriptomic signatures, and artificial intelligence-based molecular prediction models are critically discussed. Particular emphasis is placed on their biological significance, diagnostic methodologies, prognostic and predictive value, and potential role in treatment selection. A structured, database-informed narrative review identified 140 relevant publications, primarily published between January 2020 and June 2026, supplemented by earlier seminal studies and major clinical guidelines. Based on the available evidence, we propose a Clinical Actionability Framework for CRC, categorizing biomarkers into three hierarchical tiers according to their level of clinical validation and therapeutic relevance: established standard-of-care biomarkers, emerging clinical biomarkers, and future precision oncology biomarkers. Collectively, current evidence supports a progressive transition from single-gene testing toward integrated multi-omics precision medicine. Advances in comprehensive genomic profiling, liquid biopsy technologies, transcriptomics, radiogenomics, and artificial intelligence are expected to further refine patient stratification, optimize therapeutic decision-making, and facilitate the development of adaptive precision oncology models. Understanding the evolving genetic landscape of CRC is therefore essential for maximizing treatment efficacy and improving patient outcomes in the era of personalized cancer care.