According to the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5), Female Sexual Dysfunction is defined as a sexual problem associated with personal distress. It can be caused by any of the following: lack of sexual desire, impaired arousal, inability to achieve orgasm, or pain with sexual activity. Several studies have demonstrated the negative impact chemotherapy has on sexual functioning, short term and long term in women undergoing breast cancer treatment. Most of the research that has been done in this area only evaluated this problem in premenopausal women. The limited studies investigating this in postmenopausal women have found similar effects in this population group. The goal of this study is to assess sexual dysfunction in high risk postmenopausal women with breast cancer undergoing adjuvant therapy. We want to define this problem in this poorly studied subgroup, and to assess the degree of dysfunction, time course over which it occurs, and the particular sexual domains this occurs in. T This longitudinal study will assess sexual functioning utilizing two survey tools- the Female Sexual Function Index (FSFI), and the Female Sexual Distress Scale (FSDS-R). The FSFI is a 19- item questionnaire that assesses six domains of sexual functioning: desire, arousal, lubrication, orgasm, satisfaction, and pain The FSFI has been proven to have excellent validity and reliability in determining sexual dysfunction in healthy women, as well as women with various cancers including breast cancer. It was designed to be easy to use, and can be used in heterosexual, as well as homosexual women. To be consistent with the DSM 5’s definition of sexual dysfunction regarding personal distress, which is not evaluated in the FSFI, the FSDS-R will be utilized. This is a 13-item questionnaire, which has demonstrated excellent validity and reliability in determining sexual distress associated with sexual dysfunction. Participants will serve as their own control while assessing any change in sexual functioning over the course of the administration of 2-3 survey sets. The 1st set of surveys will be administered prior to receiving any treatments, this will serve as a baseline assessment for future comparison. The last 1-2 survey sets will be administered 6 months to 1 year after the initiation of adjuvant therapy. Data will be analyzed with a Repeated Measures ANOVA if statistical assumptions are met. If statistical assumptions are not met the Friedman ANOVA will be used. Post-Hoc testing will be conducted if significant main effects are found. At this time, 13 patients are currently enrolled in this trial. The number of participants for this study to achieve statistical power was calculated to be n=42. This calculation was based on one treatment group, with three observations across time, a correlation amount of repeated measures of 0.5, and a non-sphericity correction of 1.0. The assumed effect size was small to moderate with an F=0.20, an alpha of 0.05, and a beta of 0.20. Eligibility Criteria for this trial: •Must be a postmenopausal female •Diagnosed with Stage I, II, or III breast cancer •Not currently receiving endocrine therapy or chemotherapy•Plans with their physician to receive adjuvant therapy For more information please contact: Heidi Worth, MD PGY2 Internal Medicine Resident University of Tennessee Medical Center, Knoxville 904-540-1286 hworth@utmck.edu Citation Format: Heidi Worth, Timothy Panella, Clayton Bell, Mark Rasnake, Patricia Roberson, Lauren Lewis. A longitudinal study assessing sexual dysfunction in postmenopausal women with breast cancer undergoing adjuvant treatment [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr OT-02-01.