Among women at increased risk of breast cancer, fewer than 1 in 5 of those surveyed were prepared to take tamoxifen to reduce their risk, researchers report.

Tamoxifen is intended for this very use, but Dr. Joy Melnikow told Reuters Health that “women in our study were very concerned about potential harmful effects when they considered taking tamoxifen to reduce their risk for a disease they might or might not get.”

She noted that “taking tamoxifen for risk reduction is very different than taking the same drug for treatment of breast cancer, where it is widely accepted by patients.”

Melnikow, at the University of California-Davis in Sacramento, and colleagues point out in the medical journal Cancer that an estimated 2 million women in the US could experience a net benefit from taking tamoxifen.

However, according to one report, only about 5 percent of women who take tamoxifen do so to reduce their risk of breast cancer.

To gain further insight into how women weigh the risks and benefits, the researchers interviewed 255 women. The participants were given a short educational session, which included details of possible side effects of tamoxifen therapy such as a greater chance of developing endometrial cancer as well as benefits such as a reduction in fractures related to Osteoporosis.

The average risk of developing breast cancer over a 5-year period for the women in the study was estimated to be a little less than 3 percent. However, they themselves perceived their risk over this period to be about 33 percent.

Nevertheless, only 18 percent were inclined to take tamoxifen for prevention. Moreover, very high-risk women were no more likely to opt for tamoxifen than were those with a lower risk, the team found.

Despite a very high self-perceived breast cancer risk, most women appeared to have more concern about adverse effects. The researchers conclude that “candidate chemoprevention agents must have few potential adverse effects to achieve widespread acceptance.”

SOURCE: Cancer, May 15, 2005.