Minimal important differences in the EORTC QLQ-C30 in patients with advanced cancer

Aims: Quality of life (QOL) is important in patients with advanced cancer. The European Organisation for Research and Treatment of Cancer (EORTC) QLQ-C30 is a general QOL tool used in cancer patients. Often, with a large enough sample, statistical significance of changecan be reached, however the clinical significance is often unknown. This study aimed to determine the magnitude of change that is meaningful to advanced cancer patients in the EORTC QLQ-C30.

Methods: Patients completed the EORTC QLQ-C30 at baseline and 1 month post-radiation to assess changes in their QOL. Minimal important differences (MID) were calculated through anchor and distribution-based methods for improvement and deterioration. The two anchors of overall health and overall QOL were used to determine meaningful change.

Results: Statistically significant meaningful changes were seen in the use of both anchors. The overall health anchor produced a greater number of scales and symptoms that reached a statistically significant meaningful change. Meaningful change for improvement with these two anchors ranged from 9.1 units (cognitive functioning) to 23.5 units (pain), and for deterioration it ranged from 7.2 units (physical functioning) to 13.5 units (role functioning). Distribution-based estimates were closest to 0.5 SD.

Conclusion: Knowledge of meaningful change on the EORTC QLQ-C30 allows physicians to assess patients' changes over time, along with evaluating the impact of treatment on a patient's QOL. This knowledge gives insight into whether the treatment is effective and, ultimately, whether it should be continued. Knowledge of MID may assist in the determination of sample size for future trials.