Abstract
The development of the first European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Group (QLG) health-related quality of life (HRQoL) questionnaires contributed to the systematic uptake of HRQoL as an endpoint in cancer clinical trials, and to the measurement of HRQoL for individual assessment in routine care. Following a modular approach, these patient-reported outcome (PRO) measures (PROMs) ensure that both generic and disease-specific issues are assessed, enabling comparison of PROs across groups and studies. The application of a comprehensive and continually refined methodology for developing and updating these PROMs has been crucial in supporting their psychometric and cross-cultural validity, and their continued implementation in clinical research. However, the advancement of measurement science, the more widespread implementation of PROMs, and the significant evolution of anti-cancer therapies over the last decades have highlighted the need to adopt more flexible approaches to PRO assessment to ensure that PROMs remain relevant and fit-for-purpose. The QLG has responded to this call by implementing more tailored PRO measurement approaches through the development and release of the computerised adaptive test (CAT) version of the EORTC QLQ-C30 (i.e., the EORTC CAT Core) and the EORTC Item Library. The EORTC Item Library is an interactive online platform that allows for the creation of customised questionnaires (item lists) from the pool of available items derived from established EORTC QLG PROMs. The aim of this article is to describe the current EORTC QLG approach to PRO measurement in oncology, covering important historical developments and best practice recommendations.