Abstract Background: Hormone therapy (HT) significantly lowers the risk of recurrence and mortality for patients with hormone receptor-positive breast cancer, which accounts for roughly 80% of all breast cancer cases. Long-term adherence to HT can cut recurrence rates by nearly 50%. Yet, about one-third of women prescribed HT are non-adherent, taking less than 80% of the recommended daily dose. Latina patients are disproportionately affected by Non-Medical Drivers of Health (NMDoH), such as socioeconomic and access-related barriers, that hinder adherence and contribute to poorer outcomes. Objective: This three-arm randomized controlled trial evaluates the comparative effectiveness of a bilingual, culturally tailored mobile app (HT Helper) combined with Patient Navigation (PN), PN alone, and standard care on improving HT adherence. The study also examines how these interventions influence self-efficacy in recognizing and managing side effects and enhancing communication with healthcare providers. This work builds on earlier pilot findings that confirmed the HT Helper app’s feasibility and acceptability. We present key findings from the formative phase, including usability testing, focus group feedback, and final app modifications. Methods: Twelve Latina breast cancer patients receiving HT at the Mays Cancer Center and experiencing NMDoH-related barriers participated in the formative research activities. Participants used the HT Helper app for one week and then joined focus groups (conducted in their preferred language, English or Spanish) to provide in-depth feedback. Participants reviewed and commented on all app components, including navigation, educational videos, symptom-tracking tools, motivational messaging, the Chat with a Doctor feature, and the User Guide. Based on their recommendations, we updated the app and conducted a second round of testing. Findings: Most participants responded favorably to the HT Helper app, describing it as helpful, informative, and easy to use. Suggestions for improvement included expanding descriptions of specific HT-related symptoms, enhancing the app’s interactive features (e.g., Chat with a Doctor), updating patient testimonial videos, and refining the visual design of the home screen for better appeal and usability. Conclusion: A patient-driven, iterative refinement process was critical to ensuring the HT Helper app is user-friendly, relevant, and responsive to the needs of Latina patients. The resulting multi-component intervention has strong potential to improve breast cancer outcomes by enhancing medication adherence, promoting better self-management, and ultimately supporting longer-term survival. The intervention is designed to be scalable, evidence-based, and suitable for broader use among patients prescribed oral anticancer therapies. Citation Format: P. Chalela, V. Cortez, S. Sivak, A. Flores, Z. Garcia, M. Duran, S. Sierra, M. Sung-Cuadrado, A. Trejo, S. Basoor, B. Choi, E. Munoz, C. Despres, A. Gonzalez, V. Kaklamani, K. Lathrop, M. Mazo Canola, D. Inupakutika, D. Akopian, A. G. Ramirez. Advancing hormone therapy adherence among Latinas: A mobile app and navigation strategy to improve outcomes 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 PS1-04-27.
Chalela et al. (Tue,) studied this question.