Tamoxifen As Preventative?

The nation's largest group of cancer specialists is recommending that the breast cancer drug, tamoxifen, be given to healthy women at high risk for getting the disease, reports CBS News Correspondent Mika Brzezinski.

The American Society of Clinical Oncology based its decision on research that showed tamoxifen can cut a woman's risk of developing breast cancer almost in half. But critics say tamoxifen's potentially fatal side effects could end up harming healthy women. Side effects include blood clots and uterine cancer.

In a statement, cancer experts said tamoxifen "may be offered" to women who have at least a 1.7 percent risk of getting breast cancer over the next five years. That is considered a modestly increased risk.

About 29 million women, or 20 percent of the U.S. female population, are in this category - including all women over age 60.

The statement issued Tuesday was based largely on earlier research on tamoxifen, which has been available since 1978 as a treatment for breast cancer. And last year, the Food and Drug Administration said tamoxifen could be promoted as a way to prevent the disease in those at elevated risk.

However, some advocates for breast cancer patients criticized the recommendation, saying tamoxifen's health risks are too high for it to be routinely taken by healthy women.

The lead authors of the statement said a woman's personal fear of breast cancer is perhaps the most important consideration in deciding whether to take the drug.

"We are not recommending that women take it. We are recommending that women be offered it," said Dr. Rowan Chlebowski of the University of California at Los Angeles. Even then, he said, the decision to use tamoxifen "depends on a woman's actual risk and the importance of that risk to her."

Judging a woman's breast cancer risk involves a complex formula that considers her age, race, history of breast abnormalities and biopsies and family history of the disease, as well as her age at first menstruation and first childbirth. The National Cancer Institute has sent computer software for making this calculation to thousands of doctors.

The clinical oncology society committee that issued the new guidelines included four patient advocates. One of them, Helen Schiff of New York City, said she does not believe its recommendations are in women's best interests.

"Giving a powerful drug to so many healthy women is a dangerous undertaking," she said.

However, Susan Braun of the Susan G. Komen Breast Cancer Foundation in Dallas said women should, as a start, learn what their actual risk is.

"We are actively encouraging women go to their physicians and have their risk level assessed," she said. "Women both overestimate it and underestimate it."