Empowering Patients for Biomarker-Informed Care: Digital Education to Bridge HER2-Low Knowledge Gaps in Metastatic Breast Cancer

Heidi C Ko^1,2*Stuti Patel²Rachel E. Ellsworth²Michelle F. Green²Kyle C Strickland^2,3Jenessa Rossi⁴Ashima Dua⁴Maya Said⁴Amee Sato Dossey²Carole Cuny²Theresa Dunn²Kimberly Weaner²Maria Celeste Ramirez²Cristina Nelson²Linda Bohannon⁵Jonathan Klein²Marcia Eisenberg²Brian Caveney²Eric A. Severson²Shakti Ramkissoon²Rebecca A. Previs²

• ¹Labcorp Oncology, Durham, United States
• ²Laboratory Corporation of America Holdings, Burlington, United States
• ³Duke University Department of Pathology, Durham, United States
• ⁴Outcomes4Me, Boston, United States
• ⁵Vital Strategic Insights, Plainfield, United States

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 testing was accessible on the app. Responses were analyzed descriptively and reported in aggregate. Results: Of 527 respondents, 362 met eligibility criteria. Among them, 42% were diagnosed over five years ago, 35% had Stage IV disease at diagnosis, 33% received care in a community setting, and 43% had progressed on prior metastatic therapy. Most (78%, n=284) knew their HER2 status, while 18% (n=64) did not recall it and 4% (n=14) did not respond. Among those aware of their status, 51% were at least somewhat familiar with HER2-low, compared to 23% of those unaware of their HER2 status. Of patients with known HER2-negative disease (n=152), 74% reported testing within the past year, yet 51% did not recall HER2-low being discussed. Following brief in-app education, 61% of patients with unknown HER2 status at diagnosis (n=64) expressed intent to discuss HER2-low testing with their oncologist. Conclusions: Knowledge gaps in HER2 biomarker testing persist in patients with metastatic breast cancer. Even 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 HER2 status received brief education within the app, the majority expressed willingness to discuss more about HER2 testing with their oncologist.