The New England Journal of Medicine (NEJM) published results online from one study and an analysis of partial results from two others. They also were presented at the European Cardiology conference in Munich.
What we do know so far? The 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 caution until more is known.
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 exerted no difference in heart attacks, strokes or surgeries related to the valve problem but surprisingly, they noticed a higher number of cancer cases in those taking it compared to those given placebo.
Pedersen's study involved 1,873 people in Europe and the United States who were starting to have problems with their aortic valves. They were either given Vytorin or a placebo with a view that lowering cholesterol would ward off future heart problems.
Of those given Vytorin, 105 developed cancer, compared with 70 among those on placebo. That is higher than the 93 cases among Vytorin users and 65 in the others that scientists reported on a conference call in July when the issue first became known.
Cancer-related deaths were higher in all three studies.
When the results were combined, it was that found 134 among Vytorin users and 92 in the others, a result the NEJM Editors said the increase cannot simply be chalked up to chance. An interim analysis of the results of two other ongoing studies of Vytorin was performed by Sir Richard Peto and epidemiologists at Oxford University in England. Their review, reported in the NEJM, found higher rates of cancer deaths among Vytorin users, but the number of cancer cases did not significantly differ.
The accompanying NEJM editorial was brisk:
"When the cancer mortality data from the SEAS, SHARP, and IMPROVE-IT trials were combined, there was an increase in cancer mortality risk in the combined ezetimibe groups (134 deaths, as compared with 92 deaths in controls; risk ratio, 1.45; 95% CI, 1.02 to 2.05; uncorrected P=0.007). Because this P value was obtained from one of several data-driven analyses rather than from a test of a single prespecified hypothesis, it should be interpreted cautiously. The Oxford researchers believe that this finding is due entirely to the play of chance rather than to a true increase in cancer mortality. They argue that an increase in the risk of cancer death, if real, should be paralleled by an increase in the risk of cancer incidence, which was not found in the combined analysis, and that there is no plausible mechanism for such an effect."
It should be noted that whether the increased mortality risk is due solely to the play of chance remains uncertain at this stage and the data is still immature and preliminary.
Zetia interferes with the gastrointestinal absorption of cholesterol and also of other molecular entities that could conceivably affect the growth of cancer cells. The combined data from all three trials showed an increase in cancer mortality with ezetimibe may not be assumed to be a chance finding until further data are in.
We must therefore wait until more data from the ongoing trials are available, leaving doctors and patients uncertain about the drugs effects.
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