Investigating the Association Between the Urinary Microbiome and Bladder Cancer: An Exploratory Study - Beyond the Abstract

Approximately two-thirds of patients with bladder cancer will present with non-muscle-invasive bladder cancer (NMIBC). Following transurethral resection of bladder tumors (TURBT), NMIBC commonly recurs and can progress to muscle-invasive bladder cancer (MIBC). Therefore, adjuvant intravesical treatment after TURBT is recommended with chemotherapy or Bacillus Calmette-Guerin (BCG), especially for high-risk patients. While clinical and pathologic variables (such as T stage, tumor size, grade, and multiplicity) have been proposed as predictors of disease recurrence and progression, there is limited understanding of why some tumors respond to intravesical BCG while others do not.

Historically, the bladder and urine have been considered sterile in healthy individuals. Conventional microbiological methods failed to define the full spectrum of urinary bacterial species. Urinary microbiome refers to the genes and genomes of the microbiota (revealed using 16S ribosomal RNA (rRNA) sequencing), as well as the products of the microbiota and the host environment. Variation in the urinary microbiome has been associated with urological disorders, such as interstitial cystitis, urgency urinary incontinence, and neurogenic bladder dysfunction. Few reports investigated the association between urinary microbiome and bladder cancer, and most were limited by lack of variation among patients (in terms of gender, and disease status), methodological factors (sample type, storage conditions, processing and extraction techniques), and variations in bioinformatics analyses. At present, there is insufficient evidence to associate the urinary microbiome with bladder cancer.

Despite the limitations, our study showed that the urinary microbiome varied among patients with bladder cancer versus healthy controls, and also among different bladder cancer stages, male versus female patients, and in BCG responders versus non-responders. Optimizing urinary sampling and analysis are key to better understand the urinary microbiome. The exact association between the urinary microbiome and cancer is yet to be elucidated.

Written by: Ahmed Aly Hussein, MD, PhD, Assistant Professor of Oncology, Academic Clinical Associate, Department of Urology, Roswell Park Comprehensive Cancer Center, Buffalo, New York

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