Patient’s background.

Purpose
The role of intestinal flora in carcinogenesis and chemotherapy efficacy has been increasingly studied; however, comparisons between oral and intestinal flora remain limited. Given the oral microbiome’s role in systemic inflammation and immune modulation, it may significantly influence cancer progression and response to immunotherapy. This study aimed to identify the microbial changes in urothelial carcinoma (UC) by analyzing oral saliva and stool samples from healthy individuals and UC patients. We also examined the association between microbial composition and immune checkpoint inhibitor (ICI) response.
Methods
A total of 20 healthy individuals and 38 patients with UC were analyzed. Among them, 27 patients with UC underwent ICI treatment. Oral saliva and stool samples were analyzed for 16S rRNA sequences to assess bacterial composition. Operational taxonomic units were generated, and phylogenetic analysis was performed using the Illumina BaseSpace.
Results
Patients with UC showed higher Veillonellaceae and Prevotellaceae levels in saliva and stool, with lower levels of these bacteria associated with more prolonged overall survival and progression-free survival, particularly Veillonellaceae in stool. A higher neutrophil-to-lymphocyte ratio correlated with increased levels of these bacteria.
Conclusion
Veillonellaceae and Prevotellaceae are potential microbial biomarkers of survival outcomes and ICI efficacy in patients with UC. Non-invasive oral microbial sampling may facilitate personalized cancer treatment strategies.