Statins and Cancer
Abstract & Commentary
By Michael H. Crawford, MD, Professor of Medicine, and Chief of Clinical Cardiology, at the University of California, San Francisco. Dr. Crawford is on the speaker's bureau for Pfizer.
Synopsis: In older patients started on statins there was no significant increase in cancer.
Source: Setoguchi S, et al. Statins and the Risk of Lung, Breast, and Colorectal Cancer in the Elderly. Circulation. 2007;115:27-33.
Studies of statin use have shown a range of effects on cancer from a protective effect to an association between cancer and statin use in elderly patients. However, these observations have not been adequately controlled for confounders. Thus, Setoguchi and associates conducted a cohort study in an elderly population using glaucoma medication init ation as a comparison group. The study was based upon linking a state drug benefit program data to a cancer registry and Medicare utilization data. All subjects were > age 65 and were excluded if they were already in the cancer registry. The population studied was those with new statin drug use after 12 months of non-use and who filled at least 3 prescriptions in 180 days and then at least 2 per 6 months. The primary endpoint was a new diagnosis of breast, lung, or colorectal cancer. The final populations included 24,439 statin users and 7,284 glaucoma drug users. Baseline characteristics were similar with regard to health care utilization, preventive activities and other ailments, but the glaucoma drug users were older. Over a mean follow-up of 3 years, there was no difference in cancer rates between the 2 groups and they were similar to reported rates in the general population (hazard ratios 0.96-1.11, all NS). The authors concluded that in older patients started on statins there was no significant increase in breast, lung, or colorectal cancer as compared to glaucoma drug users over the period of the study.
Commentary
This study is also reassuring and should help allay patients' fears about statin use. Major efforts in this study were taken to avoid bias and confounders. The new glaucoma drug users comparison group is a major strength. This group is of a similar age and is more likely to have the same health behaviors as the statin users. Also, new statin users were studied, which avoids this bias of chronic statin users who may have more healthy behaviors. The study was large and used a cancer registry as the endpoint decision maker. Finally, they looked at an older group where cancer incidence is more likely.
There were a few weaknesses to this study. Not all potential confounders could be controlled for; such as family history of cancer, aspirin use, and obesity. However, sensitivity analyses suggested that these factors would not have made a significant difference in the results. Also, follow-up was relatively short (median 2.9 years, longest 8.4 years). Only 40% were followed for more than 3 years and 60% of the cancers occurred after 3 years. So the risk of statins with use beyond this study period cannot be ascertained. However, this study should put to rest claims that statin drugs cause cancer.
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