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Update: Can Tamoxifen Prevent Breast Cancer?

by Laura Lee Brother

Last October the first group of women in a University of Kentucky breast cancer prevention study stopped taking their pills -- the 20 milligram dose of tamoxifen or a placebo that had become part of their daily routine for the past five years. In the next few years the commitment of these women will reveal if tamoxifen, a drug used to treat breast cancer since 1971, can prevent the disease. "The goal is to see if, over time, there are fewer cases of breast cancer in the women who are taking the tamoxifen pill," says Edward Romond, principle investigator for this study and a UK associate professor of medicine.

Researchers have known for a long time that estrogen plays an active role in tumor cell growth. The hormone binds to molecules, called estrogen receptors, in the tumor cell and nourishes the cell. Tamoxifen, the chemical look alike of estrogen, will also bind to these same estrogen receptors, but it starves the tumor cell, instead of feeding it.

The 13,389 women involved in this national study, including more than 150 women at UK, are at an extremely high risk of developing breast cancer. Researchers judged each woman's cancer risk to determine eligibility for the study based on factors such as age, onset of menstruation and menopause, history of biopsies, and history of cancer in her family.

One of the challenges this study has faced is negative publicity about the potentially serious side effects of tamoxifen. Among the risks are hot flashes, rapid pulse, and a one in 600 chance of developing uterine cancer. "Anytime you break new ground, you always have to deal with criticism," Romond says. "We received very sharp criticism for including younger women in our study. The press ignored the fact that we're not treating every 35-year-old woman, and that the only 35-year-olds we included had a more than 50 percent risk of developing breast cancer.Photo of Edward Romond

"It comes down to a risk-benefit issue. There are few interventions in medicine that are totally without risk," Romond says. "The side effects and risks of tamoxifen were known long before the study started, and we explained these issues to women in great detail, because we wanted people to go in with their eyes open."

Naomi Hume, who joined the trial the September of this year, says, "Life is a risk. Whatever potential side-effects might come with tamoxifen are worth the risk to me if I can help prevent breast cancer not only for myself but for other women."

While some women in the study have experienced minor side effects and have stopped taking the medication, Rita Munn, assistant professor of medicine and a member of the tamoxifen study, says every woman who took or is still taking the drug will be checked every six months for several years for breast cancer and to find out if the problem the woman was reporting went away after she stopped taking tamoxifen.

Since the trial began in 1993, both Romond and Munn have been impressed with the dedication of the women involved in the study. "You can only learn so much about cancer in the laboratory, and that can't translate into practice without women such as these -- the credit belongs to them," Romond says.

Munn adds, "Women have been very committed to the study, and part of their motivation is to change the impact of breast cancer for all women, not just for themselves and their families."

Davis L. Gardner, who is coming to the end of her five years in the study, adds, "There's never been any doubt that I was important as who I am, and that I was not just another subject in the study. I can't emphasize enough the importance of people participating in trials such as this whenever they have the opportunity. Whether or not tamoxifen is found to be effective in preventing breast cancer, this study has increased awareness of breast cancer, and the knowledge gained through this trial will contribute greatly to future research."

Romond anticipates he and colleagues across the nation will be ready to analyze the results of this landmark study by the year 2000. "Up to this point, we have spent all of our energy trying to take care of breast cancer after the fact. This is the first study to try to do something before the fact," Romond says. "I would much rather prevent breast cancer than have to treat it. Wouldn't it be great if 200 years from now, breast cancer didn't exist on Earth? This could be the first step."

An article on this UK tamoxifen study first appeared in the Winter/Spring 1993 issue of ODYSSEY.