TAMOXIFEN CAUSES LIVER CANCER IN RATS,
MANUFACTURER SAYS

From The Cancer Chronicles #18
© 1993 by Ralph W. Moss, Ph.D.


Tamoxifen (Nolvadex) is commonly prescribed for women with breast cancer. The National Cancer Institute has launched a study to give this synthetic hormone to thousands of symptom-free women who have a family history of the disease, to see if it can prevent the illness.

But new data from the drug¼s manufacturer, Zeneca Pharmaceuticals (the new name for ICI Pharma¼s American division), has thrown serious doubt on the wisdom of that much-publicized NCI study. For, after two years¼ research, Zeneca scientists have shown that tamoxifen causes liver cancer in rats. It does so, said Dr. John Topham, a company toxicologist, not just when given in huge amounts, but at doses that overlap those found in some women taking the drug.

News of these disturbing findings began to circulate as early as 1986, Joachim G. Liehr, a University of Texas chemist told Science News (9/18/93). Liehr himself has shown that tamoxifen might pose a cancer risk. However, the Zeneca article, which appeared in Cancer Research this fall, is the first publication of the study's conclusions. These new data, says Science News, have "spawned considerable controversy over whether the federal government's cancer prevention trial might actually jeopardize some women¼s overall health."

Rats receiving just a tiny amount of the drug developed 20 to 34 times more liver tumors, many of these highly invasive. Even higher rates of such cancer were seen in rodents receiving the highest dose levels, with similarly elevated death rates. The manufacturer's own scientist concluded: "Tamoxifen must be regarded as a hepatic [i.e., liver] carcinogen in rats."

An NCI spokesperson, Susan G. Nayfield, said, "We are concerned about this" but claimed that such liver cancers are probably just "species-specific," i.e., have no relevance to the human situation. Nevertheless, she added that NCI is "very carefully" monitoring tamoxifen patients for liver problems, especially those in their 'chemoprevention' trial.

According to scientists at the American Health Foundation of Valhalla, New York, however, tamoxifen generates adducts--changes in DNA that are thought necessary for a tumor to begin. Tamoxifen's ability to alter DNA in this way "suggests that for adducts, there is no species specificity." Other studies have shown this potent drug to increase human endometrial cancer, as well as to cause circulatory and eye problems.

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Ralph W. Moss, Ph.D. is director of the The Moss Reports for cancer patients. Dr. Moss is the author of eleven books and three documentaries on cancer-related topics. He is or has been an advisor on alternative cancer treatments to the National Institutes of Health, the National Cancer Institute, the American Urological Association, Columbia University, the University of Texas, the Susan G. Komen Foundation and the German Society of Oncology. He wrote the first article on alternative medicine for the Encyclopedia Britannica yearbook. He is listed in Marquis Who's Who in America, Who's Who in the World, Who's Who in the East, and Who's Who in Entertainment (as a film documentarian). This Web site does not advocate any particular treatment for cancer. We urge you to always seek competent medical advice for all health problems, especially cancer. Before consulting our site please read our full Disclaimer statement.



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