Can Salivary Biomarkers Serve as Diagnostic and Prognostic Tools for Early Detection in Patients with Colorectal Cancer? A Systematic Review

Colorectal cancer (CRC) stands as one of the most prevalent and lethal forms of cancer worldwide with early detection playing a crucial role in improving the survival rate. Salivary biomarkers have emerged as a promising non-invasive alternative for CRC early detection. A comprehensive search of the Web of Science, Scopus, and PubMed databases was performed to identify relevant studies published between 2018 and April 2025. Inclusion criteria focused on studies analyzing salivary biomarkers in adult CRC patients, while pediatric studies, non-diagnostic applications, and studies with insufficient statistical power were excluded. A total of 12 studies were included in this review, identifying various salivary biomarkers associated with CRC. Salivary microbiota, including Fusobacterium nucleatum and other bacterial species, demonstrated potential as diagnostic markers. Metabolomic profiling revealed elevated levels of lactate and pyruvate, reflecting metabolic alterations in CRC. Several microRNAs, such as miR-92a and miR-29a, exhibited high sensitivity and specificity for CRC detection. Additionally, protein-based biomarkers, including chemerin and sHLA-G, were found to be significantly elevated in CRC patients. Salivary biomarkers show great promise as a non-invasive, cost-effective approach for CRC detection and prognosis. Their ability to reflect systemic disease processes makes them a valuable complement to existing screening methods.