Validation of the European ooncology toolkit for the self-assessment of quality of life (EUonQoL-Kit) in cancer patients and survivors: study protocol of a pan European survey

Background: European cancer programmes and policies lack a unified health-related quality of life (HRQoL) assessment tool. The European oncology quality of life toolkit (EUonQoL-Kit) is a novel set of HRQoL questionnaires, co-designed with cancer patients and survivors, translated and culturally adapted into 31 European languages, and with both static and dynamic electronic administration modes. The main aim of this study is the psychometric assessment of the static version. Secondary aims include evaluating the EUonQoL-Kit acceptability, cross-validating the administration modes, exploring individual factors potentially affecting HRQoL and HRQoL inequalities between countries. Methods: A sample of 4,500 participants, including three groups (active treatment, survivors, and palliative care) from 45 centres in 25 EU Member States and 7 associated countries, will be enrolled in a multicentre observational cross-sectional study. All participants will complete the static EUonQoL-Kit; three subsamples (each 10% of the total sample) will also respectively complete the following: a) dynamic EUonQoL-Kit, based on Item Response Theory (IRT)/Computer Adaptive Testing (CAT), b) FACT-G and EQ-5L-5D, and c) static EUonQoL-Kit (re-test). Psychometric analyses will encompass exploratory and confirmatory factor analyses (measurement model and structural validity), Cronbach's alpha (internal consistency), intraclass correlation coefficient (test–retest reliability), Pearson/Spearman correlation (concurrent validity), comparison of group scores (construct validity), and Differential Item Functioning (cross-country item equivalence). Secondary analyses will evaluate participant response time and rate, and static/dynamic score differences. Regression models will estimate associations between individual factors and HRQoL. Discussion: The EUonQoL-Kit will serve to systematically incorporate patient perspectives into European cancer policies and to address HRQoL inequalities across Europe. Trial registration: ClinicalTrials.gov Identifier: NCT05947903, 2023–06-28.