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Menopause Health Center

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Hormone Therapy May Increase Breast Cancer Risk

In new analysis, researchers found risk highest when used just before menopause


Chlebowski set out to see if the link between breast cancer risk and combined hormone therapy use was influenced by earlier use of hormones.

"We had a substantial number closer to menopause than the clinical trial of [the Women's Health Initiative]," he said.

He found, however, that not only was the risk of breast cancer still increased, but it also increased even more if the women were closer to menopause when they began to take the hormones.

He speculated that women who start the hormone therapy close to menopause still have circulating levels of estrogen high enough to make them exceed some threshold, beyond which it may become hazardous.

Progestin is thought to play a role, too, he added.

Although others have thought that the breast cancers linked with combined hormone therapy are often ones with a somewhat better outlook -- another question Chlebowski thought needed more study -- he did not find that in his new analysis.

The new analysis reinforces the finding that combination hormone therapy is linked with higher breast cancer risk, said Dr. Joanne Mortimer, director of Women's Cancer Programs at the City of Hope Comprehensive Cancer Center in Duarte, Calif.

Although previous research has found some good effects of hormone therapy on the heart, she and Chlebowski said that has to be weighed against the breast cancer risk found in much other research.

The new analysis also suggests that "the time of starting hormone therapy really matters," Mortimer said. Although the analysis found an association between the two, it did not prove a cause-and-effect link.

Mortimer and Chlebowski agreed that women need to discuss the pros and cons of hormone therapy during menopause with their doctors.

Women should seriously consider whether their symptoms, such as hot flashes and night sweats, are limiting enough to warrant taking hormones, Chlebowski said. Although some women are severely bothered by symptoms, he said, others may be less bothered and can avoid hormone therapy.

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