Comparative effects of microbiota-modifying interventions for gastrointestinal disorders in adults with colorectal cancer: a systematic review and network meta-analysis

Objectives: Chemotherapy for colorectal cancer (CRC) frequently causes gastrointestinal (GI) toxicities, which may affect treatment adherence and quality of life. These toxicities have been partially linked to chemotherapy-induced alterations in the gut microbiota. This study aimed to compare the effects of microbiota-modifying interventions on chemotherapy-related GI disorders in adults with CRC, with the available evidence primarily involving probiotic and synbiotic formulations. Methods: A systematic review and network meta-analysis (NMA) of randomized controlled trials was conducted. Electronic databases were searched for studies evaluating microbiota-modifying interventions in adults with CRC receiving chemotherapy. Pairwise meta-analyses estimated pooled effects on GI symptoms, and NMA was performed when feasible to compare interventions. Results: Twelve randomized controlled trials were included. Pairwise meta-analyses showed that multistrain probiotics significantly reduced chemotherapy-related diarrhea (odds ratio 0.48, 95% confidence interval 0.26-0.87) and showed marginal significance for nausea and vomiting (odds ratio 0.30, 95% confidence interval 0.09-0.99). NMA was feasible only for diarrhea and showed that multistrain probiotics were associated with the greatest reduction in diarrhea compared with synbiotics, placebo, and usual care. Evidence certainty was limited by the small number of studies and heterogeneity in probiotic formulations, dosages, treatment duration, and chemotherapy regimens. Conclusions: Microbiota-modifying interventions, particularly multistrain probiotics, may represent supportive strategies to reduce chemotherapy-related GI toxicity in CRC. However, current evidence remains limited and heterogeneous. Implications for Nursing Practice: Oncology nurses play a key role in assessing and managing chemotherapy-related GI symptoms. Awareness of microbiota-targeted supportive interventions may support symptom monitoring, patient education, and multidisciplinary management of treatment-related toxicities.