Drug's Affect on Breast Cancer Studied By PAUL RECER .c The Associated Press WASHINGTON (AP) - Breast cancer patients who take tamoxifen lower the overall risk of a tumor recurring. Should a new cancer develop, however, researchers find it is five times more likely to be of an aggressive type. In a study appearing Wednesday in the Journal of the National Cancer Institute, researchers at the Fred Hutchinson Cancer Research Center said the study clearly shows the benefits of taking tamoxifen to stave off new disease, but it also shows the need to find drugs to treat tumors resistant to tamoxifen. ``Half of the women who take tamoxifen develop resistance, but this resistance is not understood,'' said Dr. Christopher Li of the Hutchinson Center. The new study, he said, is consistent with a theory that tamoxifen supports the growth of breast tumors that are not sensitive to estrogen, the female hormone. This is important, said Li, because tamoxifen and other drugs work against tumors sensitive to estrogen, but ``there are no drugs that target estrogen-negative tumors.'' The study, he said, emphasizes the need for finding such drugs. Dr. Sandra Swain of the National Cancer Institute said Li's study had ``noteworthy limitations'' and was inconsistent, in some respects, with other tamoxifen studies. ``The use of tamoxifen should not be changed based on this study,'' Swain said in an interview. ``Tamoxifen has clearly increased survival for thousands of women who have used it.'' Li agreed but insisted that his study gives more insight into the effect of tamoxifen resistance among some breast cancer patients. Estrogen, the female hormone, encourages the growth of some breast cancer cells. Tamoxifen interferes with this action of estrogen by attaching itself to the molecule, or receptor, on a cancer cell surface that is also used by estrogen. This, in effect, blocks the estrogen effect on the cancer cells. Cancer cells without an estrogen receptor are not affected by tamoxifen. In the study, Li and his colleagues reviewed the medical history of almost 9,000 breast cancer patients. About half of the patients took tamoxifen as a follow up to their primary treatment, such as surgery or radiation, or both. The other half did not take tamoxifen. After eight years, the researchers found that 89 of the tamoxifen users developed cancer in the breast previously unaffected, while such tumors were found in 100 who did not use tamoxifen. Tamoxifen users had about a 10 percent overall reduced risk of developing tumors in the unaffected breast, the study showed. However, among the nontamoxifen users who developed second tumors, only 4 percent developed the more aggressive estrogen-negative cancer while for the tamoxifen users, 27 percent of the second tumors were estrogen-negative. Li said that a statistical adjustment for the data shows that tamoxifen users were 4.9 times more likely to get the more aggressive breast cancer in the second breast than were the nontamoxifen users. Li said the conclusions need to be verified by other researchers, but he emphasized that despite the finding, tamoxifen is still a powerful drug for generally lowering the risk of breast cancer recurrence. Other studies have shown that women who used tamoxifen for five years or more had a 47 percent reduction of recurrence. Li's study did not include the duration of tamoxifen use. ``I do not believe this study should change the clinical practice in regards to tamoxifen,'' he said. ``Tamoxifen does reduce the risk of a new cancer and it does improve the chances of survival.'' 7/4/01 Same Study Remember we are NOT Doctors and have NO medical training. This site is like an Encylopedia - there are many pages, many links on many topics. Support our work with any size DONATION - see left side of any page - for how to donate. You can help raise awareness of CAM.