Exploring the relationship between gut microbiota and pan-cancer: a meta-analysis of Mendelian randomization studies

The relationship between the gut microbiota and cancer is of increasing interest, but remains incompletely understood. This study synthesized evidence from Mendelian randomization (MR) studies to assess the association between genetically predicted gut microbiota abundance and pan-cancer risk. PubMed, Web of Science and Embase were systematically searched, and the results were summarized for meta-analysis. Of 157 studies evaluated, 39 met the inclusion criteria. Reporting followed PRISMA guidelines, and study quality assessed by STROBE-MR criteria indicated a low risk of bias overall. Our pooled analysis identified associations between gut microbiota and lung, breast, urological, digestive tract, colorectal and pancreatic cancers. Higher abundance of Eubacterium (OR 1.21 [1.02–1.44]) and Ruminococcaceae (OR 2.03 [1.20–3.44]) was associated with increased risk of urological tumors, whereas Parabacteroides (OR 0.87 [0.82–0.92]) was associated with decreased breast cancer risk. For lung cancer, Eubacterium (OR 0.83 [0.70–0.98]) and Ruminococcaceae (OR 0.67 [0.57–0.80]) showed inverse associations and Erysipelatoclostridium (OR 1.32 [1.10–1.58]) a positive association. Bifidobacteriaceae (OR 1.47 [1.29–1.68]) was positively associated with colorectal cancer, and Ruminococcaceae (OR 1.24 [1.05–1.48]) with pan-cancer risk. These findings may inform future cancer screening and prevention strategies, although the limited number of studies warrants further validation.