Adding home-use BIA scales, online food diaries, and tape-measures to large-scale questionnaire studies: Insights from the population-based PROFILES registry research

With the rising prevalence of cancer, longitudinal research on survivorship increasingly emphasizes patient-reported outcomes (PROs). Traditionally, these outcomes have relied on self-report questionnaires and clinical data, which provide valuable insights but may not fully capture underlying biological and physiological processes. To bridge this gap, the PROFILES registry was recently expanded to incorporate objective, home-based measures that participants can perform independently, such as food diaries, body composition scales, and activity trackers. This paper summarizes lessons learned from implementing home-use bioelectrical impedance analysis (BIA) scales, online food diaries, and tape measures to assess body composition and nutritional intake in large-scale ambulatory studies. Such studies, conducted in participants' everyday living environments rather than clinical settings, provide ecologically valid insights but also raise methodological and practical challenges. When selecting self-monitoring tools for research, reliability and validity remain essential, yet other considerations are equally important. Widely used tools facilitate comparability and generalizability across studies, while feasibility, practicality, sensitivity to change, and standardization determine their practical value. Clear instructions, efficient logistics, and user-friendliness support sustained participant engagement. Furthermore, legal and ethical requirements must be carefully addressed to ensure data privacy and compliance with regulatory standards. Integrating objective measures with PROs enhances accuracy, allows triangulation of self-reported and observed outcomes, and improves prediction of long-term survivorship trajectories. Since 2009, PROFILES data have been shared globally for non-commercial research, and upcoming expansions to include objective measures will further strengthen its impact. These experiences offer valuable guidance for future survivorship research and beyond.