Estradiol Levels in Patients Treated With Estring

Estrogen receptor positive breast cancer is the most common type of breast cancer and anti-estrogen therapy has been shown to be very effective in preventing recurrence. Side effects of anti-estrogens are due to estrogen deprivation and include hot flashes, mood changes and vaginal dryness/pain. Vaginal symptoms including pain, dryness, itching, bleeding after intercourse and frequent urinary tract infections have been reported to cause significant morbidity in postmenopausal women and higher in breast cancer survivors on anti-estrogen therapy. Treatment options include vaginal lubricants, Replens etc but unfortunately many women continue to have persistent symptoms. Local estrogen has been shown to be effective in post menopausal women (Estring or Vagifem) for their vaginal symptoms. There is a concern of using this in women with breast cancer given it may increase their blood estrogen levels. Studies done so far show have shown controversial results but majority of them report that blood estrogen levels do not change significantly. The major drawback of the studies was the sample size and inadequate accrual. The most recent trial reported showed no significant change in blood estrogen levels in women with breast cancer treated with aromatase inhibitors (anti-estrogen therapy) and were on vagifem for their vaginal symptoms. The authors reported results in 26 patients and reported no significant change in blood estrogen level. We propose to study the change in blood estrogen level when postmenopausal women with breast cancer who are currently on aromatase inhibitors are treated with Estring for their vaginal symptoms.