Postmenopausal women who take estrogen-only hormone replacement therapy for less than 10 years do not increase their risk of developing breast cancer, but the risk goes up significantly if they take the hormone replacement pills for more than 20 years, according to a new study.
Hormone replacement therapy (HRT) is widely prescribed for women in menopause who are experiencing unpleasant symptoms such as hot flashes, sleep disturbances, depression, mood swings, and anxiety. HRT can help control these side effects.
The study, published in the May 8 edition of the journal Archives of Internal Medicine, found that breast cancer risk actually decreased slightly during the first 10 years of estrogen-only HRT use. (The number of cancer cases during this period was too small to make this finding statistically significant.)
But breast cancer risk increased by a statistically significant 42 percent for women who took HRT for more than 20 years. Moreover, the risk of hormone-responsive breast cancer, the most common form of breast cancer, increased by 48 percent for women who took HRT for at least 15 years.
The researchers also reported that thinner women taking estrogen HRT for more than 20 years had a 77 percent higher risk of developing breast cancer, while overweight women had a 25 percent increased risk of breast cancer after 20 years of estrogen HRT.
HRT can contain estrogen alone, progesterone alone, or a combination of the two hormones. The Wall Street Journal reported that about 3.5 million of the 4.4 million U.S. women currently taking HRT are taking the estrogen-only form.
The research was based on Harvard University's Nurses' Health Study, and looked at estrogen use among 28,835 nurses and whether long-term use affected risk for breast cancer.
