Association of viral infection with bladder cancer: A systematic review and meta-analysis.

Background: Bladder cancer (BC) is the tenth most common cancer with the highest mortality rate. Since the etiological role of viral infection in the development of BC is less known, the aim of the present study was to examine the pooled prevalence and possible relationship between viral infection and BC.

Methods: A systematic search of major online databases was conducted to investigate relevant studies. We estimated the pooled odds ratio (OR), 95 % confidence interval (CI), and heterogeneity for all studies by using meta-analysis and forest plots. All data were analyzed using Stata Software v.14.1.

Results: We analyzed 87 articles (97 datasets), which included 59 case-control and 38 cross-sectional designs. The pooled prevalence of viral infection among BC patients was 17.59 % (95 % CI: 13.09-22.55 %; I = 96.34 %). Our subgroup analysis indicated that the pooled prevalence of human herpesvirus (HHV), papillomavirus (HPV), polyomavirus, and adenovirus was 33.67 %, 15.18 %, 7.46 %, and 30.14 %, respectively. We detected a significant relationship between viral infection and BC [summary OR 2.34 (95 % CI 1.56-3.51; I = 58.0 %)].

Conclusions: This possible association was exhibited for Epstein-Barr virus (EBV) and HPV. Our finding indicated that HPV and EBV infections with significant associations with BC can be considered as possible risk factors for BC. Although the specific molecular mechanism of the role of viruses in the development of BC has not been identified, persistent viral infection, oncogenic protein expression, apoptosis inhibition, cell cycle promotion, and disruption of signaling pathways in bladder tissue are possible pathways for the role of viruses in the development of BC.