Don't be misled by 'cancer in rodents' studies

On call

February 06, 1996|By Dr. Simeon Margolis | Dr. Simeon Margolis,SPECIAL TO THE SUN

I am concerned by a newspaper article which said that some of the drugs used to lower cholesterol can cause cancer. I have been taking lovastatin for the past three years and would like your opinion as to whether to continue taking it.

A January article in the Journal of the American Medical Association examined the frequency of cancer in rats and mice fed large amounts of several popular cholesterol-lowering drugs. The conclusions in the article were discussed in an editorial in the same issue of the journal.

Several types of cancers increased in frequence when rats or mice were fed 312 times the recommended human dose of lovastatin (Mevacor) and 10 times the dose recommended for gemfibrozil (Lopid). They also found an increase in liver cancer when blood levels in the rodents were only about four times greater than the blood levels in humans taking the highest recommended dose of lovastatin.

The prospect of increasing the risk of cancer is frightening, but you must keep certain facts in mind. First, the development of cancer in rodents taking high doses of a drug or chemical cannot predict that the drug or chemical will produce cancer in humans. Second, the animals given these substances are bred in a manner that probably increases their susceptibility to cancer. Third, the length of time the substances were given to the animals represents most of the life time of these animals, while people use them only in later life. Fourth, as cited in the editorial, about half of tested chemicals cause cancer in rodents, including 26 of the nearly 1,000 compounds in roasted coffee!

The article also discussed the possibility that the risk of cancer is increased in people with very low cholesterol levels. However, it is more likely that the very low cholesterol levels in these 'N individuals were caused by the cancer. Moreover, few patients, if any, have their cholesterol decreased to very low levels with drug treatment.

Keep in mind that there has been no reported increase in the number of cancer deaths among 27,646 patients treated with diets or various drugs over an average period of six years. Nor has there been any increase in cancer during periods of up to eight years of follow-up in these subjects after the drug or diet was stopped.

Two recent studies found no increase in the incidence of cancer in about 5,000 patients treated with two statins -- simvastatin and pravastatin -- for an average of five years.

To sum up, even the authors of the article describing cancer in rodents agree that the benefits of cholesterol-lowering drugs far outweigh any risk of cancer in those with known coronary artery disease. There may be more concern when young people are treated for many years in an effort to prevent the development of coronary heart disease, and discretion must be exercised in such situations. But it is important to keep in mind that coronary heart disease produces no symptoms until it has advanced far enough to cause sudden death or a heart attack, with resulting permanent damage to the heart.

In my opinion, the specter of cancer should not lead you to stop taking lovastatin if the drug is indicated by your cholesterol level

and risk of coronary heart disease.

Dr. Margolis is professor of medicine and biological chemistry at the Johns Hopkins School of Medicine.

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