Minimal important differences of EORTC QLQ-C30 and QLQ-BR23 for metastatic breast cancer patients in a Japanese population: results from the RESQ trial.

BACKGROUND: European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30) and breast cancer–specific quality-of-life questionnaire (QLQ-BR23) are widely used in clinical trials, but information on minimal important differences (MIDs) remain limited. METHODS: Data were obtained from the RESQ trial, a phase 3 study conducted in Japan. A total of 302 patients with HER2-negative metastatic breast cancer were randomized to receive eribulin or S-1. QLQ-C30 and QLQ-BR23 were administered every six weeks until week 24 and every nine weeks until week 42. The trial’s preplanned secondary analysis aimed to estimate group-level MIDs for both questionnaires. Subjective significance questionnaire and performance status (PS) served as anchors to estimate MIDs. RESULTS: Of the 302 patients, 270 were included in this analysis. The median age was 61 years. At baseline, 73.0% had a PS of 0, and 27.0% had a PS of 1 or 2. Within-group MIDs were estimated for 11 domains of the QLQ-C30 and 5 domains of the QLQ-BR23, ranging from 6 to 14 points for improvement and − 5 to − 17 points for deterioration. Between-group MIDs were estimated for 7 domains of the QLQ-C30, ranging from 4 to 7 points for improvement and − 4 to − 9 points for deterioration; none were estimated for the QLQ-BR23. CONCLUSIONS: This study provides the first MID estimates for the QLQ-BR23 and expands MID for the QLQ-C30 in patients with metastatic breast cancer. These findings offer benchmarks for interpreting quality-of-life outcomes and support the clinical relevance of patient-reported measures.[ 250 / 250 ].