Trial of Vaginal Estrogen for Urogenital Symptom Relief in Women on Aromatase Inhibitors

Breast cancers are made of different subtypes but by far the most common characteristic is their estrogen receptor positivity. Seventy percent of breast cancers are estrogen receptor positive and therefore responsive to the hormone estrogen, which acts as a stimulus for growth and survival of the cancer. Studies have repeatedly shown that estrogen deprivation results in prevention of breast cancer in high-risk women, and reduced recurrence of the cancer both locally and systemically as well as overall survival improvement in those women. The majority of women with estrogen sensitive breast cancer are placed on anti-estrogen therapy to prevent the cancer from returning. Even in menopause, women have estrogen produced in their bodies. Many parts of a woman's body require estrogen for normal functioning and reducing the amount of estrogen can affect women significantly in different ways. Some women have significant symptoms like vaginal dryness, which may result in painful sexual relations, discomfort, and frequent urinary tract (bladder) infections. Although the investigators goal is to reduce estrogen to prevent breast cancer from returning, quality of life (how women feel) matters during treatment which can last 5-10 years. A major question is: how medications such as Vagifem that are used to treat vaginal symptoms affect the rest of the body? This question has not been fully answered and is the reason this study is being done. The safest topical estrogen, Vagifem, is a commercially available tablet which is placed in the vagina. Vagifem works well in many women and is considered to be safe. It is used by gynecologists and cancer doctors in this setting all the time. It is not a new product and has been on the market for many years. Its effects on other parts of the body have not been tested. The investigators are poised to help answer this question by hypothesizing the following: 1. It is impossible to know what impact a given estrogen level has in distant sites, the investigators will however measure these to see if estrogen levels rise in the blood when women are treated with vaginal estrogen tablets that are commercially available. The investigators hypothesize that there will not be any elevation in measurable estrogen levels using very sensitive assays. 2. The investigators also propose using a topical vaginal estrogen application (one that is commercially available) while carefully monitoring its' effects locally in the vagina and its possible impact on bone health. The investigators expect women to have improved vaginal exams as well as improvement in overall quality of life with this treatment. It is also expected that there will be no impact on bone turnover by this topical estrogen replacement. Postmenopausal women on aromatase inhibitors interested in study participation will be asked to participate for a three month period.