TAMOXIFEN TAKES ANOTHER HIT
From The Cancer Chronicles #32-#33 © June 1996 by Ralph W. Moss, Ph.D.
In February, a branch of the United Nation's World Health Organization, the International Agency for Research on Cancer (IARC), declared that the most widely used drug for breast cancer is itself a carcinogen. It increases the risk of uterine cancer. But the agency also held that this widely used hormone - manipulating agent increased survival of post-menopausal women with breast cancer, also reduced the risk of breast cancer spreading to a second breast.
Tamoxifen is currently being given to over 10,000 healthy women who are believed to be at high risk of breast cancer, as part of a National Cancer Institute (NCI) "chemoprevention" trial. The IARC declared that "there is sufficient evidence in humans of the carcinogenicity of tamoxifen in increasing the risk of endometrial (uterine) cancer.''
On the other hand, the agency held that "the risk of endometrial cancer is far lower than the benefits women with breast cancer receive from tamoxifen.'' IARC said it was issuing the statement so that women "can make an informed decision on the treatment they will accept.''
The IARC convened 17 scientists from eight countries to judge the evidence for the cancer-causing potential of several drugs, including tamoxifen. "This process is essentially an identification of carcinogenic hazards and is not intended as a basis for risk - benefit determinations, nor for regulatory actions,'' the IARC said.
Nevertheless, it is bound to astonish many of the women who have been given the drug without adequate warnings, or who have been enrolled in the NCI's much-disputed chemoprevention trial. Tamoxifen, which has been on the market for two decades, is among the best-selling anticancer drugs in the world. It has made a small fortune for its manufacturer, ICI, and their American distributor, Zeneca, Ltd. of Delaware. A generic version is also produced by Barr Pharmaceuticals of Pomona, NY.
The IARC's determination is not really news, since papers on this link have been published for years. But it does represent a new level in public acknowledgement of the risk.
Last year, a California panel also declared the drug a carcinogen, but then faced determined opposition from Zeneca, Inc. which actually flew in scientists from the National Cancer Institute to lobby legislators to reverse the ruling. The verdict in California is still pending.