Cohort study of research trial attrition and participant-informed retention strategies among breast cancer survivors

Attrition in longitudinal cancer cohorts compromises data completeness, introduces bias, and limits generalizability. A longitudinal cohort study using data from the Cancer Toxicity (CANTO) trial among breast cancer patients quantified nonresponsiveness over time, identified factors associated with nonresponsiveness, and elicited participant-informed strategies to strengthen long-term engagement and retention. In this cohort study of 11,413 longitudinal trial participants, nonresponsiveness increased from 1.3% at year one to 25.8% at year six, and was significantly associated with lower socioeconomic status, unhealthy behaviors, synptom burden, and enrollment at smaller centers. Survey and qualitative data highlighted remote questionnaire completion, procedural support, clear communication, regular study updates, and dissemination of findings as key facilitators of sustained participation. The authors conclude that these findings call for flexible, participant-centered, and equity-oriented engagement strategies that reduce procedural burden and maintain a sense of connection to the research.