Is Vytorin Cancer Risk Real?
FAQ: Why Congress and the FDA Are Investigating Vytorin
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Why Is the FDA Investigating?
It's the FDA's job to ensure drug safety. And it probably didn't hurt that a U.S. congressional committee led by Rep. John Dingell (D-Mich.) demanded a look at the data just hours before the FDA said it would investigate.
Merck and Schering-Plough tell WebMD that they are cooperating fully with both the FDA and Congress.
But doubts remain. Still unexplained are the extra cancer deaths in patients taking Vytorin, says Nissen.
In a statement, Merck says the data show "a non-significant increase in deaths from cancer in patients in the group who took Vytorin compared to those who took placebo."
Nissen disagrees. He says the difference is highly significant and very unlikely to have occurred by chance, as Peto asserts.
"The SEAS, SHARP, and IMPROVE-IT trials, taken together, show an excess of cancer mortality associated with the Zetia-containing product Vytorin: 136 cancer deaths in treated patients vs. 95 cancer deaths in the control arms," Nissen tells WebMD.
Nissen is quick to add that the studies do not prove Vytorin causes cancer.
"The jury is still out on whether Vytorin or Zetia is associated with an increased risk of cancer," he says. "Therefore, we need careful evaluation of all the data by independent physician scientists and the FDA. And we need to be cautious about prescribing this drug until we have more data."
The FDA and the American Heart Association have warned patients not to stop taking any cholesterol-lowering drug without talking with their doctors.
How Might Vytorin Up Cancer Risk?
Vytorin contains Zocor, a statin drug -- and statin drugs do not cause cancer.
Pointing to this data, Peto says there's absolutely no reason to suspect that Vytorin can cause cancer.
"This isn't the sort of drug that is expected to have any material effect on cancer," he said at the July 21 press conference.
But Vytorin also contains Zetia. Zetia blocks absorption of cholesterol in the gut. It also blocks uptake of plant sterols, one of the healthful byproducts of eating vegetables.
In animal studies, plant sterols have an anti-cancer effect. One study shows they keep tumors from spreading.
This slim body of circumstantial evidence does not convict Zetia or Vytorin of causing cancer. Currently, neither Zetia nor Vytorin is known to cause or promote cancer or to increase cancer risk.
What is known is that Zetia and Vytorin lower cholesterol. The benefits of these drugs may outweigh any potential risks for individual patients at risk of heart disease.
WebMD writer Miranda Hitti contributed to this article.