Altered Urinary Microbiome in Patients with Bladder Cancer

Our knowledge of the role of the gut microbiome has evolved in recent years. However, less is known about the urinary microbiome. Changes in urinary microbiota have been reported in cases of urinary incontinence, pelvic pain, and bladder cancers. However, studies have produced mixed findings on whether bladder cancer is associated with an increase or decrease in the diversity of urinary microbiota. Recently, Hrbáček et al. aimed to investigate urinary microbiota changes in males with bladder cancer.

Catheterized urine was collected from 34 male bladder cancer patients and 29 male controls. The average age was higher in the bladder cancer group (71 years) than in the control group (58 years). Five patients with bladder cancer had intermediate-risk tumors, while 29 patients had high-risk tumors. Notably, participants in the control group underwent medical interventions for upper urinary tract stone disease or benign prostate hyperplasia. Overall, Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria were the dominant phyla in urine. The number of operational taxonomic units (OTUs) covering 98% of the community and the Shannon index, which reflects species diversity, significantly differed between cancer patients and controls. This indicates that patients with bladder cancer exhibited lower richness and diversity of urinary bacteria. Interestingly, OTUs from the genera Veillonella and Varibaculum were higher in cancer patients than in controls (23-fold and 8-fold, respectively). In contrast, Pasteurellaceae-related bacterium and Corynebacterium were present 18 times less in cancer patients than in controls.

This study's findings confirm significant differences in the diversity and richness of urinary microbiota in bladder cancer patients. However, a significant limitation in the study design is the lack of healthy controls. This may represent an important confounder. Moreover, control subjects were younger than cancer patients, which may represent an additional confounding factor. This study adds to our expanding understanding of urinary microbiome alterations in bladder cancer patients.

Written by: Bishoy M. Faltas, MD, Director of Bladder Cancer Research, Englander Institute for Precision Medicine, Weill Cornell Medicine

References:

Hrbáček J, Tláskal V, Čermák P, Hanáček V, Zachoval R. Bladder cancer is associated with decreased urinary microbiota diversity and alterations in microbial community composition [published online ahead of print, 2022 Nov 16]. Urol Oncol. 2022;S1078-1439(22)00344-1. doi:10.1016/j.urolonc.2022.09.018

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