LONDON, Aug. 23 (UPI) -- Women receiving a specific type of hormone treatment to ease symptoms of menopause may be at much higher risk for breast cancer -- a risk that was previously underestimated, researchers say -- according to a new study.
The Institute for Cancer Research in England found women receiving combined hormone replacement therapy, or HRT, are at about three times the risk for breast cancer as women receiving either estrogen-only HRT or tibolone, researchers found as part of a four-decade study of cancer in women.
HRT is used to treat menopause symptoms such as hot flashes, migraines, sleep problems, depression and mood swings by increasing levels of estrogen in the body.
There are three types of HRT: Estrogen-only, a combination of estrogen and progestogen, or tibolone, which is a steroid that acts like estrogen and progestogen.
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While researchers say the increased risk for cancer begins to subside once HRT has been stopped -- most women take it for a short period of time, most often in their 50s -- an accurate measure of the increased cancer risk is important for women to know.
"Our research shows that some previous studies are likely to have underestimated the risk of breast cancer with combined estrogen-progestogen HRT," Dr. Anthony Swerdlow, a professor of epidemiology at the ICR, said in a press release. "We found that current use of combined HRT increases the risk of breast cancer by up to three fold, depending on how long HRT has been used."
For the study, published in the British Journal of Cancer, the researchers recruited 58,148 women, following each for about six years from 2003 to 2009.
The researchers found women using combined HRT for a median of 5.4 years were 2.7 times more likely to develop breast cancer during the treatment period than women who have never taken the drugs. The risk increased the longer women were taking combined HRT, with those using it for more than 15 years at 3.3 times the risk for breast cancer.
Women using either estrogen-only HRT or tibolone did not exhibit the greater risk.
The researchers also note that for most women, the increased risk for breast cancer dissipated, but the fact that previous research, by their calculations, underestimated cancer risk by about 60 percent is significant. The more accurate numbers, they say, should help women make the best choice for their health.
"Whether to use HRT is an entirely personal choice, which is why it's so important that women fully understand the risks and benefits and discuss them with their general practitioner," said Baroness Delyth Morgan, chief executive of Breast Cancer Now. "We hope these findings will help anyone considering the treatment to make an even more informed decision. On balance, some women will feel HRT to be a necessity. But in order to minimize the risk of breast cancer during treatment, it is recommended that the lowest effective dose is used for the shortest possible time."
