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Breast Cancer: Topical Estrogen Risky

Study Highlights Concerns for Some Breast Cancer Patients Who Use Topical Estrogen Products
By
WebMD Health News
Reviewed by Louise Chang, MD

Jan. 25, 2006 -- Breast cancer patients taking drugs that block estrogen production should not use estrogen-based topical products to treat vaginal dryness and related problems, according to new research from the U.K.

Estrogen-based topical drugs were found to raise levels of the estrogen-hormone estradiol in patients taking aromatase inhibitors.

The findings were published today in the online issue of the journal Annals of Oncology.

Products Perceived as Safe

Aromatase inhibitors are increasingly being used to prevent breast cancer recurrences in postmenopausal women.

Drugs such as Arimidex, Femara, and Aromasin keep breast cancers from growing by interfering with the production of estrogen.

The belief that estrogen-based drugs applied directly to the vaginal area do not raise blood levels of the hormone, or raise them only slightly, has led to the perception that the products are safe for use by breast cancer patients taking aromatase inhibitors.

But that is not what Anne Kendall, MD, and colleagues at London's Royal Marsden NHS Foundation concluded when they measured hormone levels in women on the cancer drugs who were also using commercially available vaginal products containing estrogen. Commonly used vaginal estrogen products include Estrace and Premarin creams, and Estring and Femring vaginal rings.

"We feel strongly that women taking aromatase inhibitors should not be using vaginal estrogen therapy at the same time," Kendall tells WebMD.

Vaginal Problems Common

Aromatase inhibitors are increasingly replacing tamoxifen as a long-term follow-up therapy for postmenopausal patients with estrogen-sensitive breast cancers. Studies suggest that they are slightly more effective for preventing cancer recurrences in these patients.

They have also been used for several years to treat metastatic or recurrent breast cancer, but they are used only in women who have been through menopause.

Because the drugs suppress estrogen so effectively, many women experience menopausal symptoms while taking them.

About a fifth of patients on long-term aromatase inhibitor therapy suffer from atrophic vaginitis with problems that can include severe dryness, itching, inflammation, urinary urgency, and pain during sex. Atrophic vaginitis also affects many women in their postmenopausal years.

Vaginal estrogen products are very effective in the treatment of these problems, but their impact on blood estrogen levels has not been well understood.

Kendall and colleagues measured hormone levels in six women on long-term aromatase inhibitor therapy who were also using the estrogen-based vaginal tablet Vagifem. A seventh woman who was using Premarin cream was also included in the study.

The researchers measured a "significant" rise in estradiol levels in six of seven patients two weeks after the women started vaginal treatment. Levels typically fell one month into treatment but returned to pretreatment levels in only two women over seven and 12 weeks of follow-up.

"With long-term [estrogen cream] use, women may be risking the chance that their cancer may return, although this is probably not an issue as estrogen rises for only one to two months," researcher Ian Smith, MD, says.

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