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Menopause Hormone Therapy: 'Safe' Time?

New Studies Probe Timing of Hormone Replacement Therapy and Breast Cancer Risk

New Findings on Hormone Replacement Therapy continued...

Eugenia Calle, PhD, who worked on the study published in Cancer, agrees. "For women who've stopped using estrogen plus progestin, our data suggest that their risk for breast cancer will go back down in a fairly short period of time," says Calle, who recently retired as the American Cancer Society's vice president of epidemiology.

3. Mammography rates don't explain the drop in breast cancer after quitting hormone replacement therapy. Using WHI data, Chlebowski's team confirmed that breast cancer rates really did drop after women quit hormone replacement therapy; it wasn't because of a change in mammography use.

4. Breast cancer risk is greater with estrogen-plus-progestin than estrogen alone. "We do not have evidence from the WHI clinical trial that estrogen increases breast cancer. It's the combination of estrogen and progestin" that's the issue, Marcia Stefanick, PhD, tells WebMD.  Stefanick works at the Stanford Prevention Research Center and was one of Chlebowski's colleagues in reviewing the WHI data.

Calle puts it this way: "Estrogen plus progestin is considerably worse in terms of breast cancer risk than estrogen alone, and we've known that for some time."

Just taking estrogen probably isn't a solution for women who still have their uterus, because doing so would raise their risk of uterine and endometrial cancer. Women who've had a hysterectomy don't have to worry about that.

"We had a huge increase in endometrial cancer back in the '70s that was reported when women were taking just estrogen if they had a uterus. So I don't think very many people would want to go back to unopposed estrogen [estrogen without progestin] as the approach," says Stefanick.

But the studies have their differences, too.

First Two Years: 'Safe' or Not?

Calle's team looked at breast cancer risk in more than 67,000 postmenopausal women, including those taking estrogen only or estrogen-plus-progestin for at least a year or not taking any hormone therapy. The data came from an observational study; the women weren't assigned to any particular treatment plan.

The researchers identified a possible window of two to three years in which there was no sign of increased breast cancer risk in women taking estrogen plus progestin.

"In terms of our data, it looks pretty safe; there is absolutely no increased risk," Calle tells WebMD. But she cautions that that finding of a possible "safe" period "needs to be replicated in other studies ... the numbers are small in our study."

Stefanick and Chlebowski point out that taking hormone therapy can increase breast density, making it harder to spot breast cancers. "Do we have evidence that there really are fewer cancers or are we seeing that it's harder to detect them?" Stefanick asks. "If you have something that interferes with diagnosis, you're going to have a really hard conceptual time defining a completely safe interval," says Chlebowski.

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