Adjuvant endocrine hormonal therapy (EHT) is highly effective and appropriate for nearly all breast cancer patients with hormone receptor-positive tumors, which represent 75% of all breast cancer diagnoses. Long-term use of EHT reduces cancer recurrence rates and cuts the risk of death nearly in half during the second decade after diagnosis, research shows. Despite the proven benefits, about 33% of women who are prescribed EHT do not take their medication as prescribed (less than 80% take their daily dosage) and are thus at higher risk of recurrence and death.

This educational randomized controlled study will develop and pilot-test a bilingual, culturally tailored, personalized, interactive mobile application (app) in combination with patient navigation to promote and improve adherence to endocrine hormonal therapy (EHT) among breast cancer patients.

The proposed two-year study involves a 2-group randomized control trial with 3-time assessments (baseline, 3 and 6 months) and will enroll 120 breast cancer patients who are prescribed EHT and are attending the breast clinic at the Mays Cancer Center (MCC), a National Cancer Institute-designated cancer center at the University of Texas Health Science Center at San Antonio. The intervention group will receive two components: 1) a bilingual, culturally tailored, personalized, interactive mobile app; and 2) support from a patient navigator. The control group will receive the usual care and information provided by the MCC's breast clinic and pharmacy to patients undergoing oral EHT. The intervention components are based in Social Cognitive Theory and elements of Motivational Interviewing.

The proposed study aims to:

1. Develop a bilingual, culturally tailored, personalized, interactive mobile application (app) to promote and improve EHT adherence among breast cancer patients diagnosed with hormone receptor-positive breast cancer. The app will empower patients' self-monitoring and management, as well as facilitate patient education, early identification and reporting of side effects, delivery of self-care advice, and timely feedback through direct interaction between the patient and the oncology team when necessary.
2. Conduct a 2-group randomized controlled study to assess the feasibility and effectiveness of a bilingual, culturally tailored, personalized, interactive app + patient navigation (PN) to promote EHT adherence compared to usual care among patients diagnosed with hormone receptor-positive breast cancer and who are prescribed EHT.

Inclusion Criteria:

• English and Spanish speaking adult patients, 18 years of age and older who: a) are diagnosed with hormone receptor-positive breast cancer and prescribed endocrine hormonal treatment (EHT); b) own a cell phone, are able to send and receive text message and access the internet; and c) are able to provide informed consent to participate in the study.

Exclusion Criteria:

• Patients who: (a) are unable to provide consent due to a mental, emotional, or physical handicap, that keep them from understanding the consent information; (b) do not own a smart phone; (c) are unable to respond to text messages and questions or unable download the study app; d) are unable to see the app and study materials and videos (i.e., are blind, deaf)

Individual participant data won't be shared as per protocol. Results will be presented in aggregated form without any identifiers.