The Role of the Gut Microbiome in Clinical Outcomes of Colorectal Cancer: A Systematic Review (2020–2025)

The Colorectal Cancer (CRC) pathogenesis and therapeutic efficacy are influenced by the gut microbiome, making it a promising biomarker for predicting treatment responses and adverse effects. This systematic review aims to outline the gut microbiome composition in individuals with CRC undergoing the same therapeutic regimen and evaluate interindividual microbiome profile variations to better understand how these differences may influence therapeutic outcomes.

Key studies investigating the microbiome’s role in therapeutic approaches for CRC were searched in both PubMed and Cochrane databases on 12 and 22 March 2025, respectively. Eligible studies included free full-text English-language randomized clinical trials and human observational studies reporting on gut microbiome composition and treatment outcomes. RoB 2 and ROBINS-I were employed in the evaluation of bias for randomized trials and observational studies, respectively. Data extracted was narratively analyzed.

Six studies involving a total of 361 individuals were included. Therapeutic interventions, either standard treatments and/or those targeting the gut microbiome, generally increased probiotic taxa and reduced pro-carcinogenic bacteria. However, no consistent pattern of improved clinical outcomes was observed, suggesting that treatment mechanisms, the tumor’s nature, and individual characteristics play critical roles in microbiome modulation.

The gut microbiome holds significant potential in clinical settings. Nonetheless, further research is needed to better understand its functional aspects and to consider the influence of treatment mechanisms, the tumor’s nature, and individual characteristics as modulators, in order to optimize clinical outcomes.