A large study has found that people who took cholesterol-lowering drugs called statins for at least 5 years had a lower risk of developing colorectal cancer. The new results underscore the broad public health potential of statins at a time when the research window of opportunity for these drugs may be closing.

The case-control study, led by researchers at the University of Michigan Cancer Center and the CHS National Cancer Control Center in Haifa, Israel, found that people who took statins for at least 5 years had a 47 percent reduction in the risk of colorectal cancer compared with those who did not take statins.

The study included about 4,000 people in northern Israel, approximately half of whom had colorectal cancer. All were interviewed about health, lifestyle, and medication use; the most widely used statins were simvastatin (Zocor) and pravastatin (Pravachol).

The findings, published in the May 26 New England Journal of Medicine (NEJM), come 2 weeks after research presented at the American Society of Clinical Oncology (ASCO) annual meeting suggested that statins may also help prevent cancers of the breast, prostate, and lung.

"Researchers are generally finding consistent results and are encouraged," says Dr. Stephen Gruber of the University of Michigan, who co-led the colon cancer study with Dr. Gadi Rennert in Israel. "We are now trying to identify which patients are likely to benefit most from the drugs."

What distinguishes this study from previous ones is its exclusive focus on colorectal cancer and the large number of cases studied, according to a NEJM editorial by Drs. Jaye Viner and Ernest Hawk of the National Cancer Institute (NCI).

Even so, the evidence that statins prevent cancer remains largely circumstantial. "Now is not the time to start taking these drugs for cancer prevention," says Dr. Gruber. "Now is the time to study them as agents for cancer prevention."

This is exactly what Drs. Viner and Hawk say should happen, not only for cancer but for other diseases as well.

"What's really interesting here is that you have a broadly used class of agents with the potential to treat multiple diseases associated with aging, such as cardiovascular disease and cancer," says Dr. Viner, head of the Gastrointestinal and Other Cancers Research Group in NCI's Division of Cancer Prevention.

Statins, which also include atorvastatin (Lipitor), lovastatin (Mevacor), and rosuvastatin (Crestor), make up the largest segment of the prescription drug market in the United States, and their safety profiles have been determined in large, long-term cardiovascular disease studies.

But the only way to understand the unique public health potential of these drugs is to undertake carefully controlled clinical trials, Drs. Hawk and Viner argue.

"Our best hope for answering certain questions about these drugs is through placebo-controlled studies, and the window of opportunity to test statins against placebos may be about to slam shut," says Dr. Viner.

Researchers are concerned that statins, which are available in nonprescription form in the United Kingdom, may become similarly available in this country. When drugs are in widespread use among the public, it becomes more difficult to gather useful information about their effects in placebo-controlled trials, says Dr. Viner. (In January, an FDA advisory committee recommended against selling statins over the counter.)

In the meantime, several phase II, randomized, placebo-controlled studies of statins and cancer are being designed. By early 2006 or sooner, two clinical trials sponsored by NCI will begin to explore whether statins can prevent melanoma and colorectal cancer.

By Edward R. Winstead