Vaginal Estrogen Use May Counteract Anticancer Activity of Aromatase Inhibitors

Vaginal Estrogen Use May Counteract Anticancer Activity of Aromatase Inhibitors in Women with Breast Cancer

According to an article recently published in the Annals of Oncology, the use of vaginal estrogen preparations may raise estrogen levels throughout the body and may counteract the anticancer activity of aromatase inhibitors in women with breast cancer. However, women being treated with aromatase inhibitors should speak with their physician regarding their individual risks and benefits of vaginal estrogen supplementation.

Breast cancer is accountable for approximately 40,000 deaths annually in the U.S. alone. The majority of women with breast cancer have a type of breast cancer referred to as estrogen-receptor positive (ER-positive) breast cancer. This type of breast cancer is stimulated to grow by the female hormones estrogen and/or progesterone.

Women with ER-positive breast cancer are commonly treated with hormone therapy. This approach suppresses the formation of estrogen or blocks estrogen’s stimulatory effects on cancer cells.

Aromatase inhibitors (AIs) are agents that are becoming increasing used in early ER-positive breast cancer. They work by reducing the amount of estrogen in the body. Unfortunately, this comes with side effects including atrophic vaginitis (inflammation of the vagina due to thinning and shrinking tissues). This can lead to soreness, pain, itching, and painful intercourse as vaginal lubrication is decreased. Women with side effects due to atrophic vaginitis have used estrogen supplements in the vagina to improve upon these symptoms while maintaining low levels of the estrogen throughout the body.

Researchers from England recently conducted a study to evaluate female hormone levels in the blood, including estradiol (the predominant type of estrogen), in women who were using vaginal estrogen. This study included women receiving treatment with AIs for breast cancer and who were using vaginal estrogen preparations to minimize side effects caused by atrophic vaginitis. The women had blood samples taken prior to starting estrogen treatment at 2, 4, 7-10 and 12 weeks following the initiation of vaginal estrogen.

Estradiol levels increased between baseline and two weeks of vaginal estrogen treatment, but then decreased between two weeks and four weeks of treatment. However, levels at four weeks were still higher than they were at baseline. (There were, however, two patients whose estradiol levels continued to increase even after four weeks of treatment.)

The researchers caution that vaginal supplementation of estrogen increases the levels of estradiol throughout the body as determined by blood tests. For women with ER-positive breast cancer who are being treated with AIs, these increased estradiol levels may counteract anticancer activity of treatment. However, since uncontrolled side effects of AIs can reduce quality of life, further study is necessary to determine if vaginal estrogen supplementation has an effect on cancer recurrences before further conclusions are made.

Reference: KendallA, Dowsett M, Folkerd E, Smith I. Caution: Vaginal Estradiol Appears to be Contraindicated in Postmenopausal Women on Adjuvant Aromatase Inhibitors. Annals of Oncology. 2006; 17:584-587.

Related News:Aromasin® Improves Breast Cancer Outcomes Without Compromising Quality of Life(2/28/06)

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