1. What are statins?
Statins are a type of drug taken by millions of Americans to lower cholesterol. This class of drugs works by blocking an enzyme known as HMG-CoA (3-hydroxy-3-methyglutaryl COA) reductase, which the body needs to make cholesterol. Statins help to treat and prevent heart diseases by lowering blood cholesterol. In the United States, statins available by prescription include atorvastatin (LipitorTM), lovastatin (MevacorTM), pravastatin (PravacholTM), and simvastatin (ZocorTM). In the United States, statins are available by prescription only.
2. Can statins prevent cancer?
Animal research and ongoing observation of people who take statins suggests that these drugs may lower the risk of certain cancers, including colorectal and skin cancers. Statins' known benefits in preventing cardiovascular disease, along with years of strong evidence that these agents are relatively safe have led researchers to explore whether statins have the potential to prevent cancer. People should not take statins for cancer prevention outside of a clinical trial.
3. Why do scientists think statins might prevent cancer?
By exploring the effects of statins on the process of cancer at the molecular level, researchers have found that statins work against critical cellular functions that may help control tumor initiation, tumor growth, and metastasis. Specifically, statins reduce (or block) the activity of the enzyme HMG-CoA reductase, and thereby reduce the levels of mevalonate and its associated products. The mevalonate pathway plays a role in cell membrane integrity, cell signaling, protein synthesis, and cell cycle progression, all of which are potential areas of intervention to arrest that cancer process.
4. What are the common side effects of statins?
Although generally well-tolerated, statins have been associated with muscle pain (myopathy) and liver toxicity (hepatotoxicity). People who take statins should be monitored by their health care providers for these reasons.
5. Is the National Cancer Institute (NCI) supporting research testing whether statins might prevent colorectal cancer?
NCI's Cancer Prevention Clinical Trials Consortia is developing a trial for people at increased risk for colorectal cancer who also have been found to have aberrant crypt foci (ACF). ACF are clusters of abnormal cells in the lining of the colon and rectum that have been associated with the development of colorectal tumors. Using existing technology, ACF represent the earliest stage of detectable risk for colorectal cancer.
This NCI-sponsored phase II trial will begin patient enrollment in late 2005 or early 2006. The study will assess the efficacy of atorvastatin (and two other investigational agents, an anti-inflammatory, sulindac, and another compound that promotes the growth of healthy bacteria in the colon) against ACF. Paul Limburg, M.D., a researcher in gastroenterology at the Mayo Clinic (Rochester, Minn.), will be leading this multicenter effort.
6. What evidence is there that statins may have an effect on colorectal cancer?
Studies have shown that statins inhibit the growth of colon cancer cells grown in the laboratory. Consistent preventive effects of certain statins against colon cancer were first described in cancer studies in rodents published in 1994.
Some human observational studies have since suggested that statins may have protective effects against colorectal cancer. Most recently, researchers from the University of Michigan, collaborating with researchers in Israel, compared the use of statins among 1,953 patients who were diagnosed with colorectal cancer and 2,015 other people who did not have the disease. This study specifically associated a 47 percent reduction in the risk of colorectal cancer with statin use (as opposed to the use of another type of lipid-lowering drug, fibrates). [Statins and the risk of colorectal cancer. Poynter, JN., et al. New England Journal of Medicine, May 26, 2005, (352:2184-92].
7. Is NCI supporting research with statins to prevent other types of cancer?
NCI is developing a phase II placebo-controlled trial to evaluate whether lovastatin can reverse precancerous changes in atypical (so-called dysplastic) nevi, a precursor to melanoma skin cancer, and thus have the potential to prevent progression to melanoma. Ken Linden, M.D., Ph.D., a researcher in dermatology at the University of California, Irvine, will be leading this multicenter effort. The study will begin patient enrollment in late 2005 or early 2006.
8. What evidence is there that lipid-lowering drugs can prevent skin cancer?
Two large cardiovascular clinical trials have demonstrated a significant reduction in skin cancer among patients taking lipid-lowering drugs. Although clinical data do not consistently show a decreased risk of skin cancer with statin use, various human trials and preclinical studies suggest that statins may have chemopreventive activity against skin cancer.