The millions of people who take statin drugs to keep their cholesterol down may be getting an unexpected benefit. Research presented at the annual meeting of the American Society for Clinical Oncology suggests these widely prescribed drugs may help ward off colon cancer.

But experts caution that the finding is still preliminary.

"While the study's results provide a compelling rationale for more research, it is too early to recommend that patients take statins to reduce the risk of colon cancer," said lead researcher Stephen Gruber, MD, PhD, of the University of Michigan.

Gruber and colleagues studied 1,608 Israelis with colorectal cancer and 1,734 Israelis without the disease. They asked the participants about their use of statin drugs and about other lifestyle factors that could influence colon cancer risk, such as diet, physical activity, family history of cancer, cancer screening practices, and use of aspirin or similar drugs.

The people in the study who reported using statins for 5 years or more had about half the risk of colon cancer as people who did not take the drugs.

Just 267 people in the study had used statins for that long. Most of them (95%) used the drugs pravastatin (Pravachol) or simvastatin (Zocor). Other types of cholesterol lowering-drugs (like fibrates) did not have an effect on colon cancer risk.

The researchers also ruled out aspirin as a possible cause of the lowered cancer risk. Many of the patients were taking this drug regularly to prevent heart attacks, and it is also known to lower a person's chance of developing colorectal cancer. But careful analysis of their data convinced the researchers that aspirin wasn't responsible for the lowered colorectal cancer rate.

This isn't the first study to suggest statins can have an effect on cancer. Some animal and laboratory studies have suggested a protective effect. And a study presented at last year's ASCO conference found that people who used statins had a 20% lower risk of cancer than people who didn't.

While the results have been promising, more stringent studies will need to be carried out before doctors are ready to recommend statins for cancer prevention. Statins are relatively safe drugs, but they can have side effects, including potentially serious liver and muscle problems. Doctors must be certain that the benefits of cancer protection outweigh the risks of possible side effects before giving the green light for people to use statins for reasons other than cholesterol control.

A better bet for preventing colorectal cancer, said ACS experts, is to get screened regularly. Screening can find colon polyps before they turn cancerous, or detect colon cancer at its earliest stages, when it is easier to treat.