Hormone replacement therapy, which is known to increase the risk of breast cancer, also appears to make it more likely a tumor will return in women who have had the disease, researchers said on Tuesday.
Women who had earlier had breast cancer were 14 percent more likely to get it again if they used hormone replacement therapy, or HRT, researchers said in the U.S. Journal of the National Cancer Institute.
They followed for four years or longer 442 mostly Scandinavian women who had had breast cancer, half of whom had received HRT.
The women were part of a trial stopped in 2003 after concerns about the increased risk of breast cancer recurring for women on hormone therapy.
Volunteers who had received HRT got breast cancer again more than twice as often as women in the other group, amounting to an overall increased risk of 14 percent, the researchers said.
HRT was popular among menopausal women until 2002, when a major study found that it could raise the risk not only of breast and ovarian cancer, but also strokes and other serious conditions.
That study caused millions of women to abandon HRT and hit shares in makers of hormone therapies such as Wyeth.
Doctors have since stressed that younger women who need HRT drugs to relieve serious menopause symptoms such as hot flashes and vaginal dryness should still consider taking them because lower-dose formulations are now available and doctors prescribe them for short periods of time.
Hormone replacement therapy is a system of medical treatment for surgically menopausal, perimenopausal and postmenopausal women, based on the assumption that it may prevent discomfort and health problems caused by diminished circulating estrogen and progesterone hormones. The treatment involves a series of drugs designed to artificially boost hormone levels. The main types of hormones involved are estrogens, progesterone or progestins, and sometimes testosterone.
HRT is available in various forms. It generally provides low dosages of one or more estrogens, and often also provides either progesterone or a chemical analogue, called a progestin. Testosterone may also be included.
HRT is seen as either a short-term relief (often one or two years, usually less than five) from menopausal symptoms (hot flashes, irregular menstruation, fat redistribution etc.) or as a longer term treatment to reduce the risk of osteopenia leading to osteoporosis. Younger women with premature ovarian failure or surgical menopause may use hormone replacement therapy for many years, until the age that natural menopause would be expected to occur.