OP-JNCI220047 800..807

To take cancer survivorship research to the next level, it’s important to gain insight in trajectories of changing patientreported outcomes and impaired recovery after cancer. This is needed as the number of survivors is increasing and a large proportion is confronted with changing health after treatment. Mechanistic research can facilitate the development of personalized risk-stratified follow-up care and tailored interventions to promote healthy cancer survivorship. We describe how these trajectories can be studied by taking the recently extended Dutch population-based Patient Reported Outcomes Following Initial treatment and Long term Evaluation of Survivorship (PROFILES) registry as an example. PROFILES combines longitudinal assessment of patient-reported outcomes with novel, ambulatory and objective measures (eg, activity trackers, blood draws, hair samples, online food diaries, online cognitive tests, weighing scales, online symptoms assessment), and cancer registry and pharmacy databases. Furthermore, we discuss methods to optimize the use of a multidomain data collection–like return of individual results to participants, which may improve not only patient empowerment but also long-term cohort retention. Also, advanced statistical methods are needed to handle high-dimensional longitudinal data (with missing values) and provide insight into trajectories of changing patient-reported outcomes after cancer. Our coded data can be used by academic researchers around the world. Registries like PROFILES, which go beyond boundaries of disciplines and institutions, will contribute to better predictions of who will experience changes and why. This is needed to prevent and mitigate long-term and late effects of cancer treatment and to identify new interventions to promote health. Worldwide, more than 50 million people have been diagnosed with cancer in the past 5 years and are still alive (1). With continuing improvement in early detection, treatment and care, and the aging of the population, the number of survivors is growing, and they are at risk for a variety of adverse physical and psychosocial effects (2). In the past, cancer survivorship research predominantly focused on describing the long-term and late effects, applying a single exposure-to-outcome approach without including other possible exposure variables (2). Also, this approach almost solely focused on deterioration instead of changes. More recently, the focus shifted toward studies of longitudinal trajectories as our understanding of who reports changes in patientreported outcomes (PROs) and why it is still in its infancy (3). Understanding various trajectories is imperative to identify patients at risk, to prevent and mitigate long-term and late effects, and to identify new interventions to promote health. The UK National Cancer Survivorship Initiative already stated in 2011 that we need to be able to identify the risk of an individual developing ongoing problems following treatment (4). The C O M M EN T A R Y Received: July 2, 2021; Revised: November 5, 2021; Accepted: February 17, 2022 © The Author(s) 2022. Published by Oxford University Press. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs licence (https://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reproduction and distribution of the work, in any medium, provided the original work is not altered or transformed in any way, and that the work is properly cited. For commercial re-use, please contact journals.permissions@oup.com 800 JNCI J Natl Cancer Inst (2022) 114(6): djac047 https://doi.org/10.1093/jnci/djac047 First published online February 24, 2022