A decrease in breast cancer cases is associated with a decreased number of postmenopausal women taking hormone replacement therapy, a new study suggests.
Canadian researchers found that, after the therapy's risks were made known in 2002, hormone use by women dropped from 12.7 percent to 4.9 percent between 2002 and 2004. Over the same period, there was a 10 percent decrease in breast cancer cases, according to the study.
The researchers estimated how many women used the hormone replacement therapies by asking 1,200 Canadian women ages 50 to 69 whether they used the therapy between 1996 and 2006.
Hormone replacement therapy was a standard treatment for women in menopause – the hormones lessen hot flashes and other menopausal symptoms. But in 2002, the U.S. Women's Health Initiative clinical trial found that the elevated risk of cancer and stroke associated with long-term use of the therapies did not outweigh the benefits of the therapies themselves.
The researchers also found mammography rates remained stable during this time.
Breast cancer cases in Canada increased again among women in that age group in 2005, leading researchers to conclude that the hormone replacement therapy did not necessarily cause the cancer, but may have helped to promote its growth.
Therefore, by stopping the hormone replacement therapies, the growth of hormone-sensitive tumors may have only been slowed, as opposed to stopped altogether, the study said.
The study was published online today (Sept. 23) in the Journal of the National Cancer Institute.