Estrogen-Only Therapy May Reduce Breast Cancer Risk

TUESDAY, March 6 (HealthDay News) -- Some women who take estrogen-only hormone replacement therapy to stave off hot flashes, night sweats and other symptoms of menopause may be at lower risk for developing breast cancer down the road, a news study says.

Hormone replacement therapy (HRT) fell from grace rather dramatically after a large government-run trial, the U.S. Women's Health Initiative, was stopped early in 2002 because HRT was shown to increase the risk of strokes and breast and ovarian cancer. Since that time, however, some subtleties have emerged as researchers parsed the evidence further. For example, short-term use of HRT is now deemed fairly safe for some women who have severe menopausal symptoms.

The new study shows that longer-term use of estrogen-only therapy may actually lower a woman's odds of developing breast cancer. Estrogen-only therapy is reserved for women who have had a hysterectomy; women with an intact uterus who use HRT must take the hormone progestin with estrogen to prevent uterine cancer.

"Women who have had a hysterectomy may be reassured that taking estrogen by itself, short term, to relieve menopausal symptoms will not increase their risk of breast cancer," said study author Garnet Anderson of the Women's Health Initiative Clinical Coordinating Center at the Fred Hutchinson Cancer Research Center in Seattle. Women should not take estrogen to prevent breast cancer, she stressed.

The new findings were published in the March 7 online edition of The Lancet Oncology.

The North American Menopause Society recently released a position statement that backs up these findings. The group said starting combination hormone therapy (both estrogen and progestin) around the time of menopause to treat symptoms and stave off the brittle-bone disease osteoporosis is safe for some women for three to five years. Estrogen alone can be used for longer than the combination HRT, according to the society.

The new study, which was partially funded by drug manufacturer Wyeth, included more than 7,500 women from the Women's Health Initiative who took estrogen for about six years. Roughly five years after stopping treatment, the women were 23 percent less likely to develop breast cancer when compared to their counterparts who never used HRT.

Women in the estrogen group who did develop breast cancer were 63 percent less likely to die from the disease, compared to women who never took it. The lower risk of breast cancer was seen only among women without risk factors for breast cancer, such as a history of benign breast disease or a strong family history of breast cancer, the study showed.

"The story is pretty clear about estrogen plus progestin -- no matter the age of the women, estrogen plus progestin increases [the risk of] breast cancer, heart disease, stroke and blood clots," Anderson said. "These risks outweigh the benefits for all age groups."

Why estrogen alone may lower breast cancer risk while adding progestin seems to increase the risk is the million dollar question.

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Estrogen-Only Therapy May Reduce Breast Cancer Risk