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Two new studies have thrown cold water on hopes that the cholesterol-lowering drugs known as statins might prevent cancer, in addition to heart disease.

One study, published in the Journal of the American Medical Association, analyzed more than 2 dozen previous studies of statins and different types of cancer and found that the drugs didn't have any protective effect at all. The other study, conducted by American Cancer Society researchers and published in the Journal of the National Cancer Institute, found that statins did not protect users from colon cancer.

The results are in direct contrast to a study published in the New England Journal of Medicine last May, which found a significant drop in colon cancer risk among people who used statins for at least 5 years.

But the 2 new studies provide "substantial evidence" that statins don't have an impact on cancer risk, despite the previous finding, said Michael Thun, MD, ACS vice president of epidemiology and surveillance and a coauthor of the new colon cancer study.

"From the perspective of interpreting these data, it's the collective evidence that really matters, not single studies," said Thun.

Statins are the most common type of drug prescribed to lower cholesterol. Lab and animal studies have suggested statins might also have a positive effect on cancer, in particular colon cancer. Human clinical trials had mixed results, but many of these studies were small so they may not have been able to find an effect. That's what led to the current studies.

The ACS researchers looked at data from the Cancer Prevention Study II, a large, long-term study of lifestyle factors and cancer risk. More than 132,000 people were included, of whom 815 developed colon cancer. The researchers compared colon cancer risk in people who did and did not use cholesterol-lowering drugs, including statins. The risk of colon cancer was the same for both groups, even when the drugs had been used for 5 years or more. Although they did not look at statins specifically, statins were the most prescribed cholesterol medication during the study period, 1997-2001.

The second study was conducted by researchers at the University of Connecticut. They examined results from 26 randomized controlled trials of statins and cancer. In each of the trials, participants had been divided into a group that took statins and another that didn't. The trials all enrolled at least 100 people who were followed for at least 1 year. The specific statins studied included atorvastatin (Lipitor, Caduet), cerivastatin (Baycol), fluvastatin (Lescol), lovastatin (Advicor, Altoprev, Mevacor), pravastatin (Pravachol, Pravigard), and simvastatin (Zocor, Vytorin).

None of these drugs had any influence -- positive or negative -- on cancer incidence or cancer deaths, the researchers found. That remained true even when the researchers looked separately at specific cancer types and specific drugs.

The good news, Thun said, is that the study found no increased risk of cancer in people who used statins. Some studies in rodents had raised the possibility that the drugs might increase the risk of liver cancer.

"The bad news," he added, "is that based on the evidence so far, it's looking less promising that they have potential for cancer prevention."

Though statins are effective for lowering cholesterol and reducing the risk of heart disease, they should not be prescribed for cancer prevention, Thun said.

But there are things people can do right now to help lower their risk of colon cancer and other cancers, he emphasized.

Avoiding tobacco use of any kind, maintaining a healthy body weight, getting regular physical activity, and following recommended screening guidelines have all been shown to have a large impact.

"Based on what we know now, most of the effective ways of preventing cancer are not in your medicine cabinet," Thun said.

Citations: "Statins and Cancer Risk: A Meta-analysis." Published in the Jan. 4, 2006 Journal of the American Medical Association (Vol. 295, No. 1: 74-80). First author: Krista M. Dale, PharmD, University of Connecticut School of Pharmacy.

"Cholesterol-Lowering Drugs and Colorectal Cancer Incidence in a Large United States Cohort." Published in the Jan. 4, 2006, Journal of the National Cancer Institute (Vol. 98, No. 1: 69-72). First author: Eric J. Jacobs, PhD, American Cancer Society.

"Statins and the Risk of Colorectal Cancer." Published in the May 26, 2005 New England Journal of Medicine (Vol. 352, No. 21: 2184-2192). First author: Jenny N. Poynter, MHP, University of Michigan, Ann Arbor.