Abstract
PurposeTo establish minimal important differences (MIDs) for the European Organisation for Research and Treatment for Cancer Quality of life Questionnaire core 30 (EORTC QLQ-C30) in patients with metastatic breast cancer.MethodsThe dataset was obtained from the SELECT BC-CONFIRM randomized clinical trial. Anchors obtained from patients (transition items) and clinicians (performance status) were used for anchor-based methods. Anchors obtained through 6 months after starting treatment were used for this analysis. Correlation coefficients of anchor and change in QLQ-C30 and effect size were used to qualify for estimating MIDs. Mean change method and generalized estimating equation were applied to estimate MIDs. Distribution-based methods were used for comparison.ResultsWe analyzed a dataset of 154 metastatic breast cancer patients. MIDs were estimated in 8 of 15 scales of QLQ-C30. Estimated MIDs for within-group improvement varied from 7 to 15 and those for deterioration varied from − 7 to − 17. Estimated MIDs for between-group improvement varied from 5 to 11 and those for deterioration varied from − 5 to − 8 across QLQ-C30 scales. Patient-reported anchors were more susceptible to early changes in health status than clinician-reported anchors.ConclusionWe provided the MIDs of the QLQ-C30 using both patient- and clinicians-reported anchors measured in a randomized trial of Japanese patients with metastatic breast cancer. We recommend patient-reported anchors for anchor-based estimation of MID. Our results can aid patients and clinicians, as well as researchers, in the interpretation of QLQ-C30.
Highlights
Treatment for metastatic breast cancer aims to prolong survival and palliate symptoms [1]
We considered that effect sizes (ESs) ≥ 0.2 and < 0.8 were appropriate to include as minimal important differences (MIDs) because an ES < 0.2 is small, and an ES ≥ 0.8 is large [21]
The majority of patients had a history of surgery (76.6%), and about two-thirds of patients had no history of chemotherapy
Summary
Treatment for metastatic breast cancer aims to prolong survival and palliate symptoms [1]. Considering that metastatic breast cancer remains incurable, maintaining quality of life (QOL) is an important therapeutic goal [2]. Instruments to measure QOL in patients with metastatic breast cancer include the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire core 30 (EORTC QLQ-C30). Despite improvements in validation of the QLQ-C30, interpreting the numerical scores remains challenging. A large clinical trial can show statistically significant differences for QOL scores, but the clinical relevance of these differences remains controversial. The concept of minimal important difference (MID) provides a measure of the smallest difference in QOL scores that patients can
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