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The Cancer Question

There’s little doubt that hormone therapy affects a woman’s risk of malignancies.
But that’s where the clarity ends.

by Anita Slomski // Spring 2009
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Even if new research restores hormone therapy’s reputation as a tool for fighting heart disease, there remains another reason many physicians are reluctant to recommend it: cancer. It’s a complex issue, says oncologist Rowan Chlebowski, a researcher at the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center and an investigator for the Women’s Health Initiative. “Combination therapy,” he notes, “increases the risk of breast cancer, but estrogen alone may decrease it; estrogen increases endometrial cancer, but combination therapy prevents it; and combination therapy reduces colon cancer, while estrogen has no effect.”

Breast cancer is what patients of Hugh Taylor, director of the Division of Reproductive Endocrinology and Infertility at Yale University School of Medicine, fear most. And though he feels comfortable reassuring women that supplemental estrogen by itself does not cause breast cancer, according to WHI findings, he can’t do the same for women taking estrogen with progestin.

Chlebowski points out that 20,000 fewer cases of breast cancer were detected the year following the release of the 2002 WHI findings and millions of women stopped taking combination hormone therapy. And the women taking estrogen plus progestin in the WHI trial had a 43% reduction in breast cancer risk soon after they stopped the therapy. So, he says, while a woman’s risk of breast cancer returns to normal within a year or two of ending combination hormone therapy, taking estrogen with progestin for longer than five years results in a persistent doubling of breast cancer risk. “I think the risk of breast cancer has been marginalized too much,” he says.

Marcia Stefanick, chair of the WHI steering committee and a professor of medicine, obstetrics and gynecology at Stanford University School of Medicine, agrees. “The problem I have with this drumroll to get hormone therapy back on the market is that the WHI showed that combination therapy offers no benefit for cardiovascular disease, and we have very clear evidence that it increases risk of breast cancer and stroke in women 50 and older,” she says. “We have enough data to suggest that we should discourage women from taking combined hormone therapy for more than two or three years.”

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