The increase in cancer incidence among statin users was small -- about one extra case per 1,000 people, according to the study in the July 31 issue of the Journal of the American College of Cardiology.

Patients "shouldn't be scared by these results for several reasons," said lead researcher Dr. Richard H. Karas, director of preventive cardiology at Tufts-New England Medical Center, in Boston. "First, we are looking at an association -- we can't say that it is cause-and-effect. And we can't say that statins contribute to it."

People with high levels of LDL cholesterol, the "bad" kind that clogs arteries, "should continue to take their statins as prescribed by their physicians," Karas said. "From a large number of studies, it is clear that statins are a very important part of reducing people's risk of heart disease."

The study started out as a hunt for adverse side effects, such as damage to the liver and muscles, in data culled from 23 large statin trials. Karas' team did find some liver toxicity associated with higher doses of statins. But when the resulting paper was submitted to the JACC, the journal's editors asked, "What about cancer?" Karas said. "So, we went back to the drawing board."

The slight increase in cancer incidence was found in 13 trials that reported on cancer among the participants, Karas said. The increase was found in statin users who achieved the lowest LDL cholesterol levels and did not involve any specific type or location of cancer.

One expert said it's way too early to sound any alarm bells.

"Most studies don't get cholesterol levels low enough in the range where this issue comes up," said Dr. John C. LaRosa, professor of medicine and president at the State University Downstate Medical Center in Brooklyn, who wrote an accompanying journal editorial.

"You can't take this kind of data and ignore it," LaRosa said. "But we don't yet have nearly enough information to know whether this is real or a function of a longer-living population."

Cardiovascular disease is the leading cause of death in the United States, "and as the population gets older, and we postpone death from heart disease, we see people dying of other things, and cancer is right behind it," he said. "Population studies done many years ago show that the longer you live, the more likely you are to die of cancer."

The coronary benefits of statin treatment are well proven, and "this data is hardly conclusive of anything real enough to cause a change," LaRosa said.

But the study does indicate that there might be an advantage to using a variety of drugs that lower LDL cholesterol and raise blood levels of HDL cholesterol, the "good" kind that helps protect arteries, rather than just statins, Karas said. There are a variety of such drugs, including niacin, clofibrate and gemfibrozil, he said, and doctors might do a better job using multiple medications.

But the general advice for people who have been prescribed statins is to keep on taking them, said Dr. James Dove, president of the American College of Cardiology and a clinical professor of medicine at Southern Illinois University.

"The value of statins in the population at large is major compared to this small finding," Dove said. "Statins have been enormously beneficial."

Further studies are needed to determine whether there is a risk associated with very low levels of LDL cholesterol, he said.

"There has been a trend to push LDL cholesterol to lower and lower," Dove said. "If this risk proves to be true in further studies, we might not want to push it too low."

More information

The various drugs given to alter cholesterol levels are described by the American Heart Association.