More Evidence Long-Term Estrogen Therapy Raises Breast Cancer Risk

New research reveals that women who take any type of hormone replacement therapy for longer than 10 years may increase their risk of breast cancer.
Some women still use hormone replacement therapy to help ease unpleasant symptoms of menopause, which can include hot flashes, night sweats and memory problems.
Estrogen plus progesterone is prescribed for women who still have a uterus because research has shown that progesterone decreases the risk for cancer in the uterus lining. Women who no longer have a uterus because they’ve had a hysterectomy are treated with estrogen-only therapy.
Over the past decade research has gone back and forth about these drugs, raising concerns about their impact on breast cancer and heart disease. A study published just last month suggested estrogen might be good for you in the short term, but a new study presented at the American Association for Cancer Research conference in Chicago this week is the first study to examine the effects of hormone replacement therapy for longer than 10 years.

Lead study author Dr. Wendy Y. Chen of the Dana-Farber Cancer Institute in Boston, Massachusetts, says her research shows that women should be careful with long-term use of hormone replacement therapy.
In 2002, one arm of a large U.S. study – the Women’s Health Initiative (WHI) – set out to confirm that hormone replacement therapy helps prevent heart disease. It was halted when it was discovered that women in the study taking estrogen plus progesterone actually had an increased risk for invasive breast cancer, blood clots, strokes and heart disease after about five years.  While combination hormones showed some benefits including reduced hip fractures and colon cancer, the researchers determined that “harm was greater than the benefit.”
In a separate study, the WHI also looked at women who were taking estrogen-only hormone replacement therapy.  This study was stopped in 2004, when researchers detected an increased risk for stroke and blood clots.  The study found a decreased risk of breast cancer compared to women who were taking the placebo, but the difference was not statistically significant.
Chen’s current research looked at data from the Nurses Health Study from 1980 to 2008, which tracked the health of about 60,000 nurses. It looked at women who used estrogen or estrogen plus progesterone for more than 10 years and found:
– Estrogen plus progesterone use for 10 to 14.9 years had an 88% higher incidence of breast cancer
– Estrogen plus progesterone use for 15 to 19.9 years had an increase risk of “more than twofold”
– Estrogen use alone for 10 to 14.9 years had a 22% increased risk of breast cancer
– Estrogen alone for 15 to 19.9 years had a 43% increased risk of breast cancer
The research found that the risk for breast cancer did not plateau for either type of hormone therapy.  Dr. Chen notes that “there’s a continued effect over time. The longer you use it, the higher the risk.”
It’s important to keep the numbers in perspective.  According to the National Institutes of Health, when you break down the increased breast cancer risk for women in WHI taking estrogen and progesterone, the absolute risk was really low. But putting that number into percentages makes the statistics seem daunting.
“This study adds an important piece to the available evidence regarding hormone replacement therapy,” said Dr. Michael Cowher, breast surgeon at the Cleveland Clinic Breast Center. “Similar to estrogen plus progesterone therapy, there is also an increased risk to continuing estrogen alone therapy for longer than 10 years.  The initial decrease in breast cancer incidence may revert to an increase with long term usage. For women that have been on long term HRT, either estrogen alone or estrogen plus progesterone, this study may prompt a discussion with their doctor to consider stopping.”
The American Cancer Society urges women to talk to their doctors and weigh the risks and benefits of using hormone replacement therapy.  Those risks may include cancer, heart disease and blood clots.  The ACS advises women to use the lowest dose possible for the least amount of time to prevent harmful long term effects.
Despite the increased risk for developing breast cancer, the researchers did not find an increased risk for dying from breast cancer.  Chen and her colleagues are currently examining this aspect of the findings.
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