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Menopause Hormone Therapy: 'Safe' Time?

New Studies Probe Timing of Hormone Replacement Therapy and Breast Cancer Risk
WebMD Health News
Reviewed by Louise Chang, MD


Feb. 4, 2009 -- New research confirms that taking estrogen plus progestin as hormone replacement therapy for menopausal symptoms raises breast cancer risk, but that risk fades within about two years after quitting hormone therapy.

The findings come from two new studies, one published in The New England Journal of Medicine and the other in Cancer.

Here's what the researchers want women to take away from the findings:

  • It's still advisable to have hormone therapy only if needed and at the lowest dose for the shortest time to be effective. And women should weigh the pros and cons of hormone therapy in consultation with their doctors.
  • The longest "shortest time" might be as brief as two years, which some of the researchers say may be a "safe" period, though that's not certain.
  • Working with their doctors, women may want to take a break from hormone replacement therapy after three to five years to see if they still need it.
  • The increased risk of breast cancer is mostly about taking estrogen plus progestin, not estrogen alone. But about two years after quitting hormone therapy, that risk may be gone.


Hormone Replacement Therapy and Breast Cancer Risk

Hormone replacement therapy is approved to treat hot flashes and vaginal dryness related to menopause.

The Women's Health Initiative (WHI), a national women's health study, showed that long-term use (at least five years) of hormone replacement therapy combining two hormones -- estrogen plus progestin -- raised women's risk of heart disease, stroke, blood clots, and breast cancer (and lowered the risk of colorectal cancer and bone fractures) compared to women taking a placebo.

In the wake of those findings, the FDA recommended that menopausal hormone therapy using estrogens and progestins should be used at the lowest doses for the shortest duration to reach treatment goals.

But how short is the "shortest duration"? And what about hormone therapy that only includes estrogen without progestin, a treatment plan typically limited to women who've had their uterus surgically removed (a hysterectomy)? And is the breast cancer risk linked to hormone therapy reversible? Those are some of the questions tackled by the two new studies.

New Findings on Hormone Replacement Therapy

The two new studies agree on four things:

1. The long-term breast cancer risk from estrogen-plus-progestin therapy is real. Rowan Chlebowski, MD, PhD, who worked on The New England Journal of Medicine study, says that risk has been characterized as being "small," but at least 20,000 cases of breast cancer per year in the U.S. may be due to hormone therapy. "It's not a hypothetical number, something that never happens," Chlebowski tells WebMD.

2. Quitting hormone therapy cuts breast cancer risk. The increased breast cancer risk from hormone replacement therapy appears to end about two years after quitting hormone therapy. That's "good news," Chlebowski tells WebMD. In the WHI data, "it looked like the risk starts to go down right away. And after between one and two years, it looks like pretty much like that risk is gone," says Chlebowski, who works at the Los Angeles Biomedical Research Institute at the Harbor-UCL Medical Center.  

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