Heart Drug's Safety Scrutinized

July 25, 2008— -- A study that unexpectedly linked the heart drug Vytorin to excess cancer deaths has provoked controversy among heart specialists worried that the drug's risks may outweigh its benefits.

The study, called SEAS, was designed to test whether Vytorin could prevent severe, age-related heart valve problems by sharply reducing cholesterol. But lead investigator Terje Pedersen of Ulleval University Hospital in Oslo reported Monday that the study turned up a "disturbing" link to cancer.

At that same session, Oxford University experts released a separate analysis comparing SEAS data with two other ongoing studies and concluded that the cancer link wasn't "credible."

The debate rages on, with prominent heart specialists reluctant to discount the cancer risk. "Evidence like this should raise concerns," says cardiologist Harlan Krumholz of Yale University. "Patients should be aware that there's some uncertainty about the safety of Vytorin that will not be resolved until we get more definitive trial evidence."

Vytorin and its chemical cousin, Zetia, are widely prescribed. Sales for both drugs, made by Merck and Schering-Plough, total more than $4 billion a year. Both are made with the cholesterol-blocker ezetimibe; Vytorin also contains simvastatin, now a generic cholesterol-lowering drug.

The 2,000-patient SEAS study found a roughly 70 percent increase in the risk of dying from cancer. But the Oxford analysis of the two ongoing studies, called IMPROVE-IT and SHARP, found about a 33% increase in the risk of dying from cancer, considered borderline in statistical significance.

Oxford's Sir Richard Peto says he could find no pattern that could plausibly link the cancer deaths to Vytorin, such as a rise in the number of cancer deaths as exposure to the drug increases.

The evidence leaves many doctors uncertain. "Obviously, if you see it in one study, even if it's not statistically significant, you've got to be worried," says oncologist Ezekiel Emanuel of the National Institutes of Health. "Maybe this has a biological mechanism we don't know anything about."