Statin use may be associated with an increased risk of nonmuscle-invasive bladder cancer (NMIBC), a new study suggests.

In a nationwide registry study, Erik Lundberg, MD, of Umeå University in Umeå, Sweden, and collaborators compared 22,936 patients with newly diagnosed bladder cancer from 2005 to 2014 with a control group of 229,326 individuals matched by age, gender, and place of residence. A significantly higher proportion of the bladder cancer group than the control arm used statins (33.8% vs 29.8%). Statin use was associated with significant 23% increased odds of bladder cancer compared with nonuse, the investigators reported in the Turkish Journal of Urology. Subgroup analyses, however, showed

that statin use was associated with significant 31% increased odds of NMIBC, but was not associated with muscle-invasive disease.

The significant association between statin use and NMIBC was independent of the presence of diabetes mellitus, a known confounding risk factor for bladder cancer. Among cases and controls without diabetes mellitus, statin use was associated with 27% increased odds of NMIBC.

Dr Lundberg’s team noted that the reason for the increased risk among statin users is unclear, but it can be due to confounding factors associated with the concomitant use of statins. “Hypothetically, statins can affect the urothelial bladder cells by metabolic changes in the mitochondria both through the blood circulation and by a concentration of statins in the urinary bladder after excretion.”

For the study, the investigators extracted data from the Swedish National Register of Urinary Bladder Cancer, National Population Register, and Swedish Prescribed Drug Register. Strengths of the study include the large sample size and inclusion of all patients in Sweden with newly diagnosed bladder cancer, so “any risk for selection bias was reduced.” Limitations include the study’s retrospective nature and the potential risk of bias of confounding factors, such as lifestyle, metabolic disorders, obesity, and hip-to-waist ratio. In addition, the investigators had no data available on smoking, a known risk factor for bladder cancer.

Reference

Lundberg E, Hagberg O, Jahnson S, Ljungberg B. Association between occurrence of urinary bladder cancer and treatment with statin medication. Turk J. Urol. 2019;45:97-102.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6368042/pdf/tju-45-2-97.pdf