OBJECTIVES

Previous work on pooled data from five phase 3 nivolumab trials highlighted that use of the cancer-specific Quality of Life Utility Measure-Core 10 Dimensions (EORTC QLU-C10D) UK index yielded smaller quality-adjusted life year (QALY) differences between treatments than the generic 3-level EQ-5D (EQ-5D-3L) UK index on average. Since a cancer-specific utility measure might be expected to be more sensitive, this study aimed to explore the drivers of these differences.

METHODS

Associations between levels of each dimension were assessed through polychoric correlations, then a regularized partial correlation network was estimated to reduce spurious associations occurring due to background correlation between dimensions of the same instrument. These were supplemented by contingency tables, produced overall and by trial.

RESULTS

Data from 2,625 patients at baseline were available. Polychoric correlations were highest between the following respective QLU-C10D and EQ-5D-3L dimensions: Pain and Pain/Discomfort (r=0.865), Role Functioning and Usual Activities (r=0.807), Physical Functioning and Mobility (r=0.784) and Emotional Functioning and Anxiety/Depression (r=0.755). These associations were consistently significant across trials as shown by contingency tables (p<0.001). The regularized network revealed an independent association between the QLU-C10D Social Functioning and EQ-5D-3L Usual Activities dimensions. QLU-C10D symptom-related dimensions (e.g., Sleep, Bowel Problems, Appetite Loss, Nausea and Fatigue) had limited to no independent association with EQ-5D-3L dimensions.

CONCLUSIONS

This analysis facilitates a deeper understanding of potential uses of the cancer-specific QLU-C10D compared to the generic EQ-5D-3L in the evaluation of QALYs. Treatments with an impact on sleep, bowel function, appetite, nausea or fatigue will only influence QALYs as derived by the QLU-C10D; however, EQ-5D-3L utility decrements are often larger than the QLU-C10D on closely related dimensions. Therefore, increased sensitivity achieved through capturing additional dimensions in the cancer-specific measure can be counterbalanced by decreased sensitivity on the dimensions similar to the generic measure.