Long-term tamoxifen cuts breast cancer risks

The Associated Press

Breast cancer patients taking the drug tamoxifen can cut their chances of having the disease come back or kill them if they stay on the pills for 10 years instead of the five years doctors recommend now, a major study finds.

The results could change treatment, especially for younger women. The findings are a surprise because earlier studies suggested that taking the hormone-blocking drug for more than five years didn't help and could even be harmful.

In the new study, researchers found that women who took tamoxifen for 10 years lowered their risk of a recurrence by 25 percent -- and of dying of breast cancer by 29 percent -- compared to those who took the pills for just five years.

Some women balk at taking a preventive drug for so long, but for those at high risk of a recurrence, "this will be a convincer that they should continue," said Dr. Peter Ravdin, director of the breast cancer program at the UT Health Science Center in San Antonio. The study was presented Wednesday at a breast cancer conference in San Antonio and published by the British medical journal Lancet.

About 50,000 of the roughly 230,000 new cases of breast cancer in the United States each year occur in women before menopause.

Tamoxifen long was the top choice, but newer drugs called aromatase inhibitors -- sold as Arimidex, Femara, Aromasin and in generic form -- have less risk of uterine cancer and other problems. However, the newer drugs don't work well before menopause. Even some women past menopause choose tamoxifen over the newer drugs, which cost more and have different side effects such as joint pain, bone loss and sexual problems.

In the new study, researchers in England assigned 6,846 women who already had taken tamoxifen for five years to either stay on it or take dummy pills for another five years.

It found 15 percent of women who had stopped taking tamoxifen after five years had died of breast cancer versus 12 percent of those who took it for 10 years. Cancer had returned in 25 percent of women on the shorter treatment versus 21 percent of those treated longer.

Tamoxifen had some troubling side effects: Longer use nearly doubled the risk of endometrial cancer. But it rarely proved fatal.