Serum Estradiol Levels In Postmenopausal Women With Breast Cancer Receiving Adjuvant Aromatase Inhibitors and Vaginal Estrogen

Inclusion Criteria: * History of breast cancer, stages I-III with pathology confirmed at MSKCC * Women who have completed all of their primary treatment (surgery, radiation therapy, adjuvant chemotherapy) with the exception of endocrine therapy and currently have no clinical evidence of disease. * Women who are currently on aromatase inhibitors for at least three months--either letrozole or anastrozole * Women with symptomatic urogenital atrophy: vaginal dryness, irritation, pruritus, dyspareunia, urinary frequency and/or urinary incontinence * Menopausal at study entry defined as: * Bilateral salpingo-oophorectomy independent of age * If natural menopause, age ≥ 50 with cessation of menses for at least 12 months * If menopause induced by chemotherapy, age ≥ 50 with no menstrual period at least 12 months after chemotherapy finished * At least 18 years of age * Able to participate in the informed consent process * Gynecology examination within six months * Able to read/speak English Exclusion Criteria: * Inability to give informed consent * Vaginal bleeding of unknown etiology within 12 months of study entry * History of prior vaginal 17-β estradiol or other topical estrogen use within the past six months