title: Evidence-based guidelines for interpreting change scores for the European Organisation for the Research and Treatment of Cancer Quality of Life Questionnaire Core 30.
abstract: OBJECTIVE
  To use published literature and experts' opinion to investigate the clinical meaning and magnitude of changes in the Quality of Life (QOL) of groups of patients measured with the European Organisation for the Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30).
  
  
  METHODS
  An innovative method combining systematic review of published studies, expert opinions and meta-analysis was used to estimate large, medium, and small mean changes over time for QLQ-C30 scores.
  
  
  RESULTS
  Nine hundred and eleven papers were identified, leading to 118 relevant papers. One thousand two hundred and thirty two mean changes in QOL over time were combined in the meta-analysis, with timescales ranging from four days to five years. Guidelines were produced for trivial, small, and medium size classes, for each subscale and for improving and declining scores separately. Estimates for improvements were smaller than respective estimates for declines.
  
  
  CONCLUSIONS
  These guidelines can be used to aid sample size calculations and interpretation of mean changes over time from groups of patients. Observed mean changes in the QLQ-C30 scores are generally small in most clinical situations, possibly due to response shift. Careful consideration is needed when planning studies where QOL changes over time are of primary interest; the timing of follow up, sample attrition, direction of QOL changes, and subscales of primary interest are key considerations.
authors.affiliation: Clinical Trials Research Unit, University of Leeds, UK. kim.cocks@york.ac.uk
authors.forename: K
authors.initials: K
authors.lastname: Cocks
authors.forename: M T
authors.initials: MT
authors.lastname: King
authors.forename: G
authors.initials: G
authors.lastname: Velikova
authors.forename: G
authors.initials: G
authors.lastname: de Castro
authors.forename: M
authors.initials: M
authors.lastname: Martyn St-James
authors.forename: P M
authors.initials: PM
authors.lastname: Fayers
authors.forename: J M
authors.initials: JM
authors.lastname: Brown
mesh_terms: D019317:Evidence-Based Medicine; D017408:Guidelines as Topic; D006801:Humans; D015201:Meta-Analysis as Topic; D009369:Neoplasms / Q000523:psychology*; D011788:Quality of Life; D011795:Surveys and Questionnaires