Gut microbiome dysbiosis and cancer: A systematic review on the emerging role of probiotics in oncology.

OBJECTIVE

To evaluate the role of probiotic supplementation in cancer patients and its clinical effects.

ELIGIBILITY CRITERIA: English-written clinical trials, pooled-, or meta-analyses of clinical trials assessing probiotic treatments in cancer patients.

INFORMATION SOURCES: PubMed, Scopus, and Web of Science databases up to September 2025.

METHODS FOR SYNTHESIS OF

RESULTS

Narrative synthesis of included studies, stratified by assessed outcomes.

INCLUDED STUDIES: 3 clinical trials, 1 in vivo study followed by a clinical trial, 2 meta-analyses and 1 pooled analysis.

SYNTHESIS OF

RESULTS

Across chemotherapy settings, probiotic supplementation was associated with a reduction in clinically relevant diarrhea, with the most consistent signal for severe diarrhea and for selected subgroups (e.g., patients with colostomy during irinotecan-based therapy). Meta-analytic evidence also supported improvements in other gastrointestinal (GI) symptoms (nausea/vomiting, bloating, anorexia). In surgical oncology, perioperative probiotics/synbiotics were associated with faster GI functional recovery and favorable recovery-related markers in individual trials, while pooled randomized evidence in colorectal surgery indicated fewer postoperative infections and shorter length of stay; effects on anastomotic leak were inconsistent. Controlled clinical studies did not report probiotic-strain invasive infections, although rare serious events have been described in broader evidence.

LIMITATIONS OF EVIDENCE: Heterogeneity in study designs, formulations, and outcome definitions; limited reporting of resource-utilization outcomes and adverse-event attribution; few large-scale trials; scarce direct oncologic efficacy endpoints.

INTERPRETATION: Probiotics appear to be a promising adjunct for supportive care in selected cancer pathways, particularly for GI toxicity and perioperative outcomes. Strain-defined, adequately powered trials with harmonized endpoints are needed to inform guideline-ready use.