A Patient-Led Survey of Antibody Drug Conjugate Usage and Dosing for People Living With Metastatic Breast Cancer

Scientific advancements have led to more people living longer with metastatic breast cancer (MBC). Antibody-drug conjugates (ADCs) offer a promising treatment option, but currently approved ADCs are associated with significant side effects that can impact quality of life. Dose reductions may help mitigate these effects, yet little is known about real-world, patient-reported experiences with ADC dosing. We surveyed 170 individuals with MBC who had received ADC treatment to assess initial dosing, dose modifications, and barriers to supportive care. Most respondents (94.1%) began treatment with the recommended dosing frequency and 82.9% with the recommended dose. However, 35.3% reported dose reductions, primarily due to experienced or anticipated side effects. Open-ended responses underscored the burden of side effects: "If not for low dose, I don't think I could go on." Most participants (81.0%) reported oncologist-led efforts to manage side effects, and 73.0% used medications for symptom control. Financial barriers were common, with 43.5% reporting difficulty accessing supportive care. These findings highlight the need for patient-centered dosing strategies and improved access to supportive care.