The Potential Role of Urinary Microbiota in Bladder Carcinogenesis: A Systematic Review

Recent advances in molecular analysis and non-culture-based technologies have allowed researchers to identify the diverse number of microorganisms residing in our body environment called microbiota. The characteristics of urinary tract microbial communities might be affected by the risk factors of bladder cancer (BC) which is the fourth most frequent cancer in males and relatively common in females.

These findings have led researchers to hypothesize that there might be a missing link between the development of BC and changes in the urinary microbiota. In this systematic review, a total of 27 studies comprising 1338 individuals were included, and among them, 926 were BC patients and 412 were controls. Fifteen studies compared the microbiota of BC patients with that of control subjects, while the other 12 studies included only BC patients with muscle invasive (MIBC) or non-muscle invasive BC (NMIBC). The most common sample collection methods were midstream urine, pre-cystoscopy, TURB or surgery catheterization, or voided urine. In most studies, there were reported significant differences in alpha diversity in patients with BC compared to the healthy controls or between NMIBC and MIBC, or across tumor grades. The included studies indicate that the composition of urinary microbiota is altered in patients with BC, but no clear conclusions can be made. The sample collection method is highly heterogeneous requiring standardization.

The significantly enriched suspicious genera in the urine of patients with BC varied between the different studies. There is no doubt that further research is necessary to uncover the role of microbiota in BC carcinogenesis, invasiveness, progression, and metastasis as well as a predictor/monitor of therapy.

Written by: Sakineh Hajebrahimi, MD, Chair, Professor of Urology Department, Tabriz University of Medical Sciences, Tabriz, Iran

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