Statins use increases the risk of urinary tract cancer: Preliminary results of a nationwide population‐based case‐control study

Abstract

Dear Sir, Statins, cholesterol-lowering drugs commonly prescribed for the prevention of coronary heart disease, have been actively investigated for their effects on cancer risk and cancer prevention. However there are still no consistent results for this. 1–5 Khurana et al. reported that statins seem to be protective against the development of renal cell carcinoma after controlling for age, sex, smoking and obesity, with an adjusted OR 0.52 (95% confidence interval (CI) 0.45–0.60). 4 Interestingly, a recent large population-based case-control study demonstrates that the prolonged use of statins (for more than 4 years) was associated with a significantly increased risk of bladder cancer (OR 1.29, 95% CI 1.08–1.54). 2 We have been conducting a nationwide populationbased case-control study investigating the association between prolonged exposure to non-steroidal antiinflammatory drugs (NSAID) and statins on the risk of urinary tract cancer (UTC), including prostate and renal cancer. We postulated that exposure to these two classes of commonly prescribed drugs up to certain quantities and for a certain duration may have some interaction on the risk of developing UTC. This study utilized the Taiwan National Health Insurance Research database (NHIRD) which contains a number of large computerized databases that include registration files and original data on claims’ reimbursement that are derived from the insurance system held by the Bureau of National Health Insurance (NHI), Taiwan. These databases are maintained by the National Health Research Institutes, Taiwan, and are provided to researchers for academic research purposes. The Taiwan NHI program started on 1 March 1995. As at 2007, 98.4% of Taiwan’s population of 22.96 million individuals have been enrolled in this program. The NHIRD data files are de-identified by scrambling the identification codes of both the individuals and medical facilities. This study adhered to strict confidentiality guidelines that are in accordance with the regulations regarding personal electronic data protection. The study population consists 7680 cases of newly diagnosed UTC in the year 2007. A control group individually matched by one patient to three controls on gender, age and the index date (date of first-time diagnosis of UTC) of case was retrieved. Exposure to NSAID or statins in the 5 years prior to UTC diagnosis was then investigated. The statins studied are lovastatin, simvastatin, pravastatin and atorvastatin, all in oral tablet dosage form. Most of the prescriptions were one tablet (pill) of any statin a day. The results on association of statin use with subsequent risk of UTC show that any use of a statin is associated with an increased risk with an OR of 2.61 (95% CI, 2.51–3.16). As can be seen from Table 1, the risk of UTC increases in terms of duration of use and total dose. Greater than 12 months exposure to any statin available in Taiwan harbors an OR of 6.10 (95% CI, 3.05–12.20). Greater than 600 pills of any of the studied statin use posts a risk with an OR of 7.62 (95% CI, 2.96–19.65). This corresponds to 600 days of regular dose of statin. Since the renal pelvis, ureter, urinary bladder and urethral cancer, mostly urothelial tract cancer, account for up to 46.39% of the case group, our study result supports those of other authors. 2 In conclusion, the result of the ongoing analysis strongly shows that statin use increases the subsequent risk of UTC in the Taiwanese population.