MUNICH, Germany — Results from three studies of the cholesterol-lowering drug Vytorin are not enough to prove or rule out a possible link to a higher risk of cancer, so the drug should be used with great caution until more is known, editors of a leading medical journal urged Tuesday.

The New England Journal of Medicine published results of the studies, which also were presented at a cardiology conference in Munich.

Vytorin is a combination of Merck's Zocor, a long-sold statin drug, and Schering-Plough's Zetia, a newer type of medicine that lowers cholesterol in a different way.

The possible cancer risk unexpectedly arose in July, when Dr. Terje Pedersen of Oslo, Norway, announced preliminary results from a study testing whether Vytorin could prevent damage to the heart's aortic valve from worsening.

The drug did not help the valve problem. But doctors saw a greater number of cancer cases in those taking it compared to others given dummy pills.

That prompted an interim analysis of results of two other ongoing studies of Vytorin by scientists at Oxford University in England.

"I don't think there is any evidence of hazard here," concluded Sir Richard Peto, a cancer epidemiologist.

But editors of the medical journal, which published the initial study and Peto's analysis, said a link cannot be ruled out, and that patients and their doctors "are unfortunately left for now with uncertainty" about the safety and effectiveness of the drug.

Other doctors also were not convinced that Vytorin is safe.

"I think the jury is still out as to whether there's a cancer signal," said Dr. Gordon Tomaselli, chief of cardiology at Johns Hopkins Hospital, and spokesman for the American Heart Association. Tomaselli was not connected to the research.

Pedersen's study followed 1,873 patients in Europe and the United States who were starting to have problems with their aortic valves. Patients were either given Vytorin or a placebo. Of patients on Vytorin, 105 developed cancer, compared with 70 among those on placebo.

Some doctors suggested that the hypothesis behind the trial was mistaken, and that heart valve problems can only be solved with surgery, not with medication.

But they said the drug is still useful for people who need their cholesterol lowered — if other drugs do not work.

"If I was on this medication and it was the only way to get my cholesterol down, I would not change my therapy based on this," said Dr. Douglas Weaver, president of the American College of Cardiology. The group has been asked by the U.S. Senate to account for the money it accepts from pharmaceutical companies, including Merck.

The New England Journal of Medicine editors had a staff statistician look at combined cancer deaths from all three Vytorin studies. They say the extra risk "should not be assumed to be a chance finding" until more information is in.

With other options available for heart patients, some doctors said there was no obvious reason to take Vytorin. "There's no proof that this combination is working," said Dr. Christer Hoglund, a cardiologist at Sweden's Karolinska Institute.

"We don't know that this drug is bad, but we don't know that it's any good either."

AP Business Writer Linda A. Johnson in Trenton, N.J. and AP Medical Writer Marilynn Marchione in Milwaukee, Wis. contributed to this report.