Abstract P5-10-20: Patient awareness of HER2-low in metastatic breast cancer: survey results in a patient-facing app

Abstract Background: The emergence of trastuzumab deruxtecan has led to significant improvement in clinical outcomes for patients with HER2-low metastatic breast cancer, which accounts for about half (45-55%) of breast cancer diagnoses. However, little is known about patients’ awareness of diagnostic testing requirements and treatment implications associated with HER2-low status. This study aims to better understand patients’ knowledge of HER2-low. Methods: This cross-sectional survey was completed virtually on the Outcomes4Me mobile app, a direct-to-patient digital application that empowers patients to take a pro-active approach to their care. Eligible patients included those with Stage IV breast cancer living in the United States. Participants were surveyed on awareness of their tumor’s HER2 biomarker status and willingness to discuss more with their oncologists if their status was unknown. Educational content about HER2 biomarker testing was accessible on the app. Responses were analyzed descriptively and reported in aggregate. Results: In total, we received responses from 527 patients, of which 362 met eligibility for inclusion. Of the evaluable patients, 41.9% (152/362) were diagnosed over five years ago, 35.4% (128/362) had Stage IV disease at diagnosis, 32.9% received treatment in a community setting (119/362), and 43.4% (157/362) had progressed on at least one prior therapy for metastatic cancer. Sixty-four (18%) patients did not know or recall their HER2 status at diagnosis; 14 (3.9%) provided no response. Of the 284 (78.5%) patients who were aware of their HER2 status at diagnosis, 24 (7%) reported having HER2-low breast tumors. Within the cohort of patients with known HER2 status, 119/284 (41.9%) of patients were not at all aware or not very aware of the HER2-low classification. Almost 43% (112/284) of patients with a known HER2 status reported HER2 testing within the last year, but 51.3% (57/111) of patients who were classified as HER2-negative following their most recent testing did not recall their oncologist discussing HER2-low as a possibility. For patients with an unknown biomarker status, brief education about HER2 testing was provided within the app. After engagement, 60.9% (39/64) of patients with unknown HER2 status felt very or somewhat likely to talk to their oncologist about testing for HER2-low. Conclusions: Knowledge gaps in HER2 biomarker testing persist in patients with Stage IV breast cancer. For patients with a known HER2 status, many remain unaware of the HER2-low classification. Digital education resources such as the Outcomes4Me app can facilitate patient empowerment and provide targeted education outside of traditional clinical settings, enabling shared decision making. After patients with an unknown status received brief education within the app, the majority expressed willingness to discuss more about HER2 testing with their oncologist. Citation Format: Heidi Ko, Michelle F. Green, Kyle C. Strickland, Maureen Cooper, Jenessa Rossi, Ashima Dua, Maya Said, Amee Sato Dossey, Carole Cuny, Theresa Dunn, Cristina Nelson, Linda Bohannon, Maggie Chapman, Jonathan Klein, Marcia Eisenberg, Brian Caveney, Eric A. Severson, Shakti Ramkissoon, Rebecca A. Previs. Patient awareness of HER2-low in metastatic breast cancer: survey results in a patient-facing app [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P5-10-20.