Minimally important differences for the EORTC QLQ-C30 in prostate cancer clinical trials

• Main Authors: Eva M. Gamper, Jammbe Z. Musoro, Corneel Coens, Jean-Jacques Stelmes, Claudette Falato, Mogens Groenvold, Galina Velikova, Kim Cocks, Hans-Henning Flechtner, Madeleine T. King, Andrew Bottomley, on behalf of the EORTC Genito-Urinary Tract Cancer Group and Quality of Life Groups
• Format: Article
• Language: English
• Published: BMC 2021-10-01
• Series: BMC Cancer
• Subjects: Health-related quality of life; HRQOL; HRQL; Interpretation of scores; MIDs; Patient-reported outcomes
• Online Access: https://doi.org/10.1186/s12885-021-08609-7

Abstract Background The aim of the study was to estimate the minimally important difference (MID) for interpreting group-level change over time, both within a group and between groups, for the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30) scores in patients with prostate cancer. Methods We used data from two published EORTC trials. Clinical anchors were selected by strength of correlations with QLQ-C30 scales. In addition, clinicians’ input was obtained with regard to plausibility of the selected anchors. The mean change method was applied for interpreting change over time within a group of patients and linear regression models were fitted to estimate MIDs for between-group differences in change over time. Distribution-based estimates were also evaluated. Results Two clinical anchors were eligible for MID estimation; performance status and the CTCAE diarrhoea domain. MIDs were developed for 7 scales (physical functioning, role functioning, social functioning, pain, fatigue, global quality of life, diarrhoea) and varied by scale and direction (improvement vs deterioration). Within-group MIDs ranged from 4 to 14 points for improvement and − 13 to − 5 points for deterioration and MIDs for between-group differences in change scores ranged from 3 to 13 for improvement and − 10 to − 5 for deterioration. Conclusions Our findings aid the meaningful interpretation of changes on a set of EORTC QLQ-C30 scale scores over time, both within and between groups, and for performing more accurate sample size calculations for clinical trials in prostate cancer.