A study published in this week’s Journal of the National Cancer Institute suggests that tamoxifen may be even more effective than was originally thought at reducing the incidence of breast cancer among high-risk women.
The five-year study followed 13,000 women who were at high risk for getting breast cancer. Women were given either tamoxifen or a placebo each day for several years.
The breast cancer rate among women taking tamoxifen was 22 per 1,000, only half that of the 43.4 per 1,000 women who developed breast cancer while taking a placebo. Women who had already suffered non-invasive breast cancer or atypical hyperplasia (breast growth disease) reduced their risk even more — by 56 and 86 percent, respectively.
While the findings were overwhelmingly positive, tamoxifen did cause serious side effects. It doubled rates of uterine cancer and tripled their likelihood of developing a potentially life-threatening blood clot. Tamoxifen was also linked to cataracts and found ineffective in treating estrogen-receptor negative cancers, which are believed to be among the least-treatable cancers.
Preliminary findings from this research were released in April of this year, when researchers, thrilled with tamoxifen’s positive results, discontinued the use of placebos and allowed all research subjects to take tamoxifen.