Multi-Organ Metastasis in Early-Onset Colorectal Cancer: Emerging Patterns, Biological Drivers, and Therapeutic Implications

Early-onset colorectal cancer (EOCRC), defined as colorectal cancer diagnosed before the age of 50 years, has become an emerging global health concern due to its steadily increasing incidence. Compared with late-onset colorectal cancer, EOCRC often presents with more advanced disease and exhibits distinct clinical and biological characteristics. Notably, younger patients are more likely to present with synchronous metastases and multi-organ dissemination at the time of diagnosis. This mini-review summarises current evidence regarding metastatic patterns and the biological mechanisms underlying multi-organ metastasis in EOCRC. The liver remains the most common metastatic site in EOCRC, primarily due to portal venous drainage from the colorectal region. However, studies suggest that EOCRC patients have a higher likelihood of additional metastatic involvement of the lungs, peritoneum, and distant lymph nodes, with occasional spread to the bone and brain. Several biological mechanisms may contribute to this aggressive metastatic behaviour. Distinct molecular alterations, including KRAS and BRAF mutations and microsatellite instability, have been reported in EOCRC and may influence tumour progression and metastatic potential. In addition, tumour microenvironmental changes such as epithelial–mesenchymal transition and angiogenesis play critical roles in facilitating tumour invasion, intravasation, and colonisation of distant organs. Hereditary predisposition, lifestyle-related risk factors, and gut microbiome alterations have also been implicated in EOCRC pathogenesis. A clearer understanding of the metastatic cascade and its molecular drivers in EOCRC is essential for improving early detection and developing targeted therapeutic strategies. Future research integrating molecular profiling and clinical outcomes may help optimize personalised treatment approaches and improve prognosis in this increasingly recognised patient population.