Vaginal estrogen is commonly used to treat genitourinary syndrome of menopause, but is it safe for women who have been diagnosed with breast cancer?
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Currently, more than 3.8 million breast cancer survivors reside in the United States, reflecting high prevalence as well as cure rates for this common malignancy.
When over-the-counter measures including vaginal lubricants and moisturizers are not adequate, vaginal estrogen may be a highly effective treatment for genitourinary syndrome of menopause (GSM), a common condition associated with hypoestrogenism that impairs sexual function and quality of life.
Use of vaginal formulations does not result in systemic levels of estrogen above the normal postmenopausal range. Nonetheless, the US Food and Drug Administration lists a history of breast cancer as a contraindication to the use of all systemic as well as vaginal estrogens.
In premenopausal women, chemotherapy for breast cancer often results in early menopause. Aromatase inhibitors, though effective in preventing recurrent disease in menopausal women, exacerbate GSM. These factors result in a high prevalence of GSM in breast cancer survivors.
Because the safety of vaginal estrogen in the setting of breast cancer is uncertain, investigators at Johns Hopkins conducted a cohort study using claims-based data from more than 200 million US patients that identified women with GSM who had previously been diagnosed with breast cancer. Among some 42,000 women diagnosed with GSM after breast cancer, 5% had three or more prescriptions and were considered vaginal estrogen users.
No significant differences were noted in recurrence-free survival between the vaginal estrogen group and the no estrogen group. At 5 and 10 years of follow-up, use of vaginal estrogen was not associated with higher all-cause mortality. Among women with estrogen receptor–positive tumors, risk for breast cancer recurrence was similar between estrogen users and nonusers.
However, concomitant use of vaginal estrogen and aromatase inhibitors was associated with a higher risk for breast cancer recurrence than was use of vaginal estrogen alone.
Although this important study's findings have the limitations characteristic of observational studies, its large size and careful analyses suggest that in selected well-counselled breast cancer survivors, off-label use of vaginal estrogen may safely improve their sexual function and quality of life.
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