Association between occurrence of urinary bladder cancer and treatment with statin medication.

OBJECTIVE: The incidence of urinary bladder cancer (UBC) has increased in Sweden despite decreased smoking, indicating that other factors might be associated. The increased use of statin medication for elevated blood lipids might be one such influencing factor. The aim of the present study was to assess whether statins are afflicted with an increased incidence of UBC.

MATERIAL AND METHODS: Data from the Swedish National Register of Urinary Bladder Cancer, National Population Register, and Swedish Prescribed Drug Register were extracted. There were 22,936 patients with new diagnosed UBC between 2005 and 2014. Statin prescription was defined as any medication prescribed with the Anatomical Therapeutic Classification code C10A. For each patient, 10 control individuals were matched by age, gender, and living area, comprising 229,326 individuals. The Cochran-Mantel-Haenszel test was used to evaluate the hazards ratios.

RESULTS: Statins were more frequently used in patients with UBC (33.8%) than in controls (29.8%, p<0.0001). The use of statins was afflicted with a 23% increased odds ratio (OR) for UBC (OR 1.23 (1.19-1.27), p<0.001). Subgroup analyses showed that an increased OR was found in non-muscle invasive UBC only. There was a tendency that OR was stronger for men and for younger patients. Limitations include its retrospective register-based design and potential risk of bias of confounding factors, such as smoking and body mass index.

CONCLUSION: This nationwide register study suggests an association between the occurrence of UBC and patients using statins. The association was found in patients with non-muscle invasive disease only. Confounding factors, such as smoking, cannot be overruled.