Measurement Properties of the EQ-5D-5L and EQ-5D-3L in Six Commonly Diagnosed Cancers

This study aimed to compare the measurement properties of the EQ-5D-3L (3L) and EQ-5D-5L (5L) in cancer patients. A consecutive sample of inpatients with lung, breast, colorectal, liver, gastric, or thyroid cancer were interviewed using the 3L, 5L, and Functional Assessment of Cancer Therapy–General (FACT-G) questionnaires, and a subgroup was invited to complete the 3L and 5L again. Kappa and intraclass correlation coefficient were used to assess test–retest reliability, and Spearman’s correlation between the EQ-5D and FACT-G was evaluated to assess convergent validity. Comparison of subgroups defined using Eastern Cooperative Oncology Group status and cancer stage were performed to assess known-group validity and discriminatory power using the F-statistic and area under the receiver-operating characteristics curve. All analyses were also performed for each subgroup of cancer patients. A total of 416 cancer patients completed the baseline questionnaire and 90 patients also completed the follow-up survey after 2 days. Ceiling effects were smaller in 5L (10.1%) than in 3L (17.8%). The test–retest reliability and convergent validity of the 5L were slightly better than those of the 3L. Both the 3L and 5L showed known-group validity; however, the 5L index showed better discriminatory power. Similar trends were found in the six types of cancers. In general, 5L appears to have better measurement properties than 3L for measuring the health-related quality of life of cancer patients. While both the 3L and 5L are suitable, 5L should be preferable to 3L for use in cancer outcomes research.