Abstract Background. Currently, sexual orientation data is not collected, nor is the language to study sexual orientation data defined by any national cancer database. Due to this limitation, little is known about breast cancer (BC) disparities in sexual minority women (SMW) despite several studies showing increased lifestyle risk factors. Our objective was to study this question in the All of Us database. Methods. We analyzed data from the All of Us research program, a national open enrollment database that registers diverse subjects through associated healthcare electronic medical records and collects survey data. We aimed to compare risk factors, as well as preventative and procedural healthcare utilization differences between SMW and straight women (StW) as they relate to BC care. Results were expressed as odds ratios (OR) with a 95% confidence interval [CI]. Results. Of 229,917 cisgender women who answered the sexual orientation question, 27,302 (11.9%) selected “non-straight orientation, prefer not to answer, or skipped” and thus were defined as SMW. In total, 6,905 (3.0%) women had received a BC diagnosis, including 423 (6.1%) SMW. SMW were less likely to have a BC diagnosis than StW (OR 0.48 [0.43-0.53]). Among all women, there were significant differences in frequency and types of visits and procedures performed. SMW women were less likely to undergo annual history and physical examination (0.79 [0.73-0.85]), mammography (0.61 [0.53-0.69]), and breast biopsy (0.55 [0.41-0.72]), as well as being less likely to undergo breast surgeries (mastectomy 0.53 [0.30-0.93]; lumpectomy 0.53 [0.38-0.74]). Survey data revealed differences in several lifestyle factors that relate to BC risk development. While StW were more likely to answer yes to being an “alcohol participant” (0.79 [0.77-0.82]), SMW reported higher rates of alcohol intake on a daily, weekly, and monthly basis, as well as being more likely to consume 6 or more drinks in one sitting. SMW also showed significantly increased history of smoking/nicotine usage. There were also significant differences in healthcare access and utilization: StW were more likely to receive health advice from a primary care provider (0.65 [0.65-0.69]), while SMW were more likely to utilize urgent and emergency care (1.44 [1.34-1.54]). SMW were also more likely to report being unable to afford care (1.82 [1.72-1.93]), medication (1.69 [1.61-1.76]), specialty care (1.98 [1.89-2.08]), and follow-up care (1.85 [1.75-1.95]), as well as to delay care due to cost concerns about the copay (2.13 [2.02-2.23]), deductible (1.64 [1.56-1.73]), paying out of pocket (1.70 [1.63-1.77]) or because they were nervous (2.80 [2.69-2.91]). SMW reported being more likely to experience healthcare discrimination based on questions about healthcare provider interactions (Table 1). Conclusions.Although likelihood of a breast cancer diagnosis in the All of Us database is significantly higher in StW than SMW, discrimination, lack of access, and underutilization of preventative and screening services by SMW likely creates an underrepresentation of the true number of SMW with BC. Further studies on characteristics at diagnosis, treatments, and survival are needed to address how these disparities affect BC outcomes in SMW. Table 1: Survey answers among sexual minority women (SMW) compared to straight women (StW) reporting on discrimination from healthcare provider interactions in the All of Us database. SMW: sexual minority women; StW: straight women; OR: odds ration; Lower 95 CI: lower 95% confidence interval; Upper 95 CI: upper 95% confidence interval; Sig. *: statistically significant with p < 0.05; OR>1: SMW most likely to answer; OR <1 StW most likely to answer. Citation Format: Lucas Houser, Collin Dougherty, Sean Figy, Jessica Maxwell, Juan Santamaria-Barria. Breast Cancer Care Disparities in Sexual Minority Women: An Analysis of the National Institutes of Health All of Us Research Program [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-09-11.