Abstract PS1-03-03: Patient experience with intramuscular vs oral endocrine therapy in metastatic breast cancer

Abstract Background: Endocrine therapy (ET) is commonly used in the treatment of breast cancer, including both oral and intramuscular (IM) options. While ET is an effective treatment for breast cancer, the two administration modes may generate disparate burdens and benefits on patients’ everyday lives. This study aims to explore metastatic breast cancer (MBC) patients’ experiences with ET by describing the burdens (including challenges to administration and adherence), benefits, and preference of oral and IM ET. Method: Adults in the US with a history of taking both oral and IM ET consecutively for their MBC for at least 3 months completed an online survey. Participants were recruited via email and in-person at Cancer Support Community’s national network of 190 locations and 14 advocacy groups. Participants provided sociodemographic information and clinical history. Survey content included assessment of treatment-related considerations for oral and IM ET administration (i.e., convenience, pain, time, transportation, remembering, cost, access, distress, impact on eating) on a 5-point scale of burden vs. benefit (major or minor burden, neutral, major or minor benefit), and preference for oral vs IM ET. Participants also rated the importance, on a 5-point scale (not at all important to very important), of 11 factors when considering their MBC treatment options. Data collection is ongoing; results and conclusions are based upon interim data. Results: Interim data include responses from 100 women with MBC with a mean age of 54 years (range: 29-78), 69% non-Hispanic White, 24% urban. The average time since metastatic diagnosis was 6.6 years (median = 6). Approximately 58% of participants lived more than 30 minutes away from a treatment center. Duration on ET was longer for oral (median = 28 months) than for IM (median = 17 months); 76% indicated they started oral prior to IM ET. More than 80% of participants responded that oral ET was less painful to take, required less transportation and time, and was more convenient compared to IM ET. Most (65%) reported that oral ET interfered less with daily life compared to IM (17%). Top benefits of oral ET included ease of access (71% [major or minor benefit]), minimal time commitment (64%), and convenience (60%), while the stress or anxiety associated with having to take daily medication was the most common burden (37% [major or minor burden]). For IM ET, the main benefit reported was ease of remembering (60%), while the most frequently reported burden was pain or discomfort from the injection (84%). When comparing treatment modalities, 63% preferred oral, 18% preferred IM, 12% expressed no preference, and 7% were unsure. Self-reported adherence was better for IM vs oral ET, with 84% and 57% reporting they never missed a single dose, respectively. Among the 41% that missed at least one dose for oral ET, 88% missed ≤3 times a month. When asked about treatment priorities, nearly all participants (98%) found the ability to slow disease progression when considering treatment options an important priority (quite important or very important) followed by the ability to cure the disease (87%) and impact of treatment on daily life (85%). Conclusions: Findings suggest a clear preference for oral over IM ET, with most participants citing ease of access, convenience, and minimal disruption to daily life as benefits to oral ET. However, having to take oral medication daily was associated with stress and anxiety for some. Although self-reported adherence was better for IM ET, missing a single dose has different implications for the IM ET, which is given every 28 days, rather than daily like oral ET. While benefits and burdens are observed for both modes of administration, oral therapy is clearly preferred. These findings support the need for shared decision-making to help ensure treatment decisions are optimized with patient preferences. Citation Format: E. Fortune, A. Newell, R. Speck, A. Gilligan, M. Gonzalo, A. Searles Vitko. Patient experience with intramuscular vs oral endocrine therapy in metastatic breast cancer [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS1-03-03.