Scientists confirm tamoxifen works but say it isn't for everyone
May 27, 1999
Web posted at: 1:50 PM EDT (1750 GMT)
By Laura Lane
Last year's excitement about tamoxifen wasn't all hype. After an additional year of study, researchers are confirming that the drug is continuing to show promise in preventing breast cancer.
Last year, scientists announced that tamoxifen reduced the risk of breast cancer by 45 percent in a study that involved 13,000 American women at risk for the disease. This year, those results are being supported by further study, which show that tamoxifen also prevents certain types of growths from developing into cancer. The researchers from the Boston Medical Center in Boston, Massachusetts discussed their findings Tuesday at the 35th annual meeting of the American Society of Clinical Oncology.
Breast cancer is the third leading cause of cancer deaths in the country. With more than 175,000 women diagnosed with the disease every year, breast cancer is the most common cancer among women.
The new study
The Boston researchers focused their study on 2,019 women who participated in the original study and had developed either a lobular carcinoma in-situ or an atypical hyperplasia, growths that are typical warning signs of breast cancer.
Women with hyperplasia who took tamoxifen were 86 percent less likely to develop breast cancer than women who took a sugar pill. Those with carcinoma in situ who took tamoxifen reduced their risk of the disease by 66 percent.
However, women need to focus on their chances of developing breast cancer when making a decision to take tamoxifen, said Dr. Rowan Chlebowski, professor of medicine at Harbor-UCLA Medical Center in Los Angeles, California. Because the drug does have side effects, women need to assess how much benefit they will reap from taking the drug. The drug's side effects include an increased risk for developing endometrial cancer, blood clots and cataracts. "These therapies aren't for everyone for now because it depends on how a woman perceives her risk of developing breast cancer," Chlebowski said.
But the drug's potential to prevent cancer can far outweigh the small chance that a woman will be harmed by side effects, said Dr. George Peters, executive director of the University of Texas Southwestern Center for Breast Care, whose center participated in the original tamoxifen study. "Let's not diminish the effect of tamoxifen by this side effect," said Peters, referring to endometrial cancer. "One needs to be aware of those side effects, but one who's at a higher risk of developing breast cancer needs to have something available to them."
Tamoxifen has been used to treat breast cancer since 1978 and was approved last year to be used for breast cancer prevention by the U.S. Food and Drug Administration.
Candidates for tamoxifen
Chlebowski co-chaired a committee within the American Society of Clinical Oncologists, which convened to examine all research surrounding tamoxifen and raloxifene, a drug that also received publicity last year because of its potential cancer-preventing properties.
Committee members issued their findings and recommendations during a conference meeting in May. The report concludes that women who are 35 years old and over with a 1.7 percent chance of developing breast cancer during the next five years may be candidates for taking tamoxifen. About 29 million American women are in this category.
The committee recommended additional study of raloxifene, which is already FDA-approved to prevent osteoporosis.
However, not all scientists are impressed with the tamoxifen studies. Dr. Trevor Powles, professor of breast oncology at the Royal Marsden Hospital in London, England, did not see tamoxifen reduce breast cancer risk among the 2,471 women he studied.
Many of the women were at high risk for breast cancer and were resistant to any preventive effects of tamoxifen, he said. In the American study, the women may have been more susceptible to the drug because they were at lower risk for developing breast cancer.
Powles explained that some at-risk women may end up taking the drug and not be able to benefit while exposing themselves to harmful side effects. These women may fare better undergoing treatment if they actually develop the disease, he said.
Copyright 1999 by WebMD, Inc. All rights reserved.
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