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Estrogen-Alone HRT May Be Breast Safe

Study Finds Breast Cancer Risk Due to Progestins in HRT
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WebMD Health News

March 5, 2003 -- Women who take combination hormone replacement therapy for more than four years are at very high risk of breast cancer compared with women who have never used HRT. But estrogen-only HRT is virtually free of breast-cancer risk, a Swedish study suggests.

The findings, from a study of some 30,000 women age 25-65, appear in the March 15 issue of Cancer, the journal of the American Cancer Society. Researchers Håkan L. Olsson, MD, PhD, and colleagues at University Hospital, Lund, Sweden, interviewed the women between 1990 and 1992. They then followed their health status through 2001. Nearly 3,700 of the women said they'd used various forms of HRT.

As did the U.S. Women's Health Initiative (WHI) study, Olsson's team found that HRT containing progestins raised breast-cancer risk. This risk more than quadrupled in women who used continuous progestin/estrogen HRT. It more than tripled in women using progestin-only HRT, and more than doubled in women using sequential progestin/estrogen HRT -- continuous estrogen doses with periodic progestin doses

"We found that all HRT preparations containing progestins raise the risk for breast cancer -- considerably higher than we thought before," Olsson tells WebMD. "After four years, combined progestin/estrogen HRT -- whether continuous or sequential -- and progestin-only regimens give women a high risk of breast cancer."

In stark contrast, women who received estrogen-only HRT had no added breast-cancer risk.

"I think this study has a positive message," Olsson says. "We are able actually to tailor a hormone therapy for a woman with menopausal symptoms that will minimize her risk of breast cancer. But the present combined agents are not good. So if women must use them, it should be for less than two years."

Estrogen is the heart of HRT. But estrogen alone raises a woman's risk of uterine cancer. Nature's way of dealing with this problem is to increase estrogen levels during part of the menstrual cycle, and to increase progesterone levels during another part of the cycle. Progestin -- synthetic progesterone -- mimics this cycle. But the way it's been used in the past clearly substitutes breast-cancer risk for uterine-cancer risk.

Olsson sees three ways out of this dilemma:

  • For women who have had hysterectomies, estrogen-only regimens appear safe.
  • Giving low-dose progestin -- perhaps locally, with a special IUD -- could help protect the uterus against estrogen without too much breast-cancer risk.
  • Different types of progestin -- so-called androgenic forms such as tibolone -- might not increase breast-cancer risk. But this would have to be demonstrated in clinical trials.

The new findings don't surprise New York ob-gyn and author Laura Corio, MD. Corio says she stopped prescribing progestin in 1999.

"If women have to take HRT because of menopausal symptoms, we give them low-dose natural progesterone and estrogen," Corio tells WebMD. "We have used micronized progesterone since 1999 and we see no breast cancer. Women should not use Provera, but the oral micronized form -- either Prometrium or one that is compounded for them."

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