SABCS: Tamoxifen's Benefits Persist After Therapy Stops
Update of IBIS-I study shows high-risk women continue to have reduced risk of breast cancer
MONDAY, Dec. 18 (HealthDay News) -- Updated results of IBIS-I, a worldwide breast cancer prevention study, confirm that tamoxifen reduces the risk of estrogen receptor-positive breast cancer in high-risk women by about one-third and this benefit persists for at least another several years after treatment is stopped, according to research presented this week at the 29th annual San Antonio Breast Cancer Symposium.
Jack Cuzick, Ph.D., of the Wolfson Institute of Preventive Medicine in London, U.K., and colleagues randomly assigned 7,145 women in seven countries to receive either 20 milligrams of tamoxifen or a placebo every day for five years.
The researchers found that the tamoxifen group developed 34 percent fewer estrogen receptor-positive breast cancers than the placebo group but that there was no clear benefit in women who concurrently took hormone replacement therapy. They also found that tamoxifen's cancer-protective effects persisted for at least another five years after treatment was stopped and that women were no longer at excess risk of tamoxifen-related side effects such as endometrial cancer and blood clots after treatment was stopped.
"As most side effects of tamoxifen stop after the five-year treatment period, this suggests that the risk-benefit ratio will continue to improve with longer follow-up time," the authors conclude.