Abstract P6-05-43: Validity of EQ-5D-5L for women with breast cancer
Authors: Torres Sofia , Trudeau Maureen , Liu Geoffrey , Mitsakakis Nicholas , Bayoumi Ahmed 
Published: March 2023

Abstract
Background: The EuroQol- 5 Dimension (EQ-5D) is a generic patient-reported outcome measure widely used to capture meaningful change in health-related quality of life between treatments to inform drug and health technology reimbursement decision making. We investigated the construct validity of EQ-5D-5L in women with breast cancer.
Methods: This study included adult women diagnosed with stage I to IV breast cancer, who completed the EQ-5D-5L and the Edmonton Symptom Assessment System (ESAS) during outpatient clinic visits at two academic cancer centres in Toronto. We evaluated construct validity through assessing known-group validity and convergent/divergent validity. For known-group validity, the primary analysis tested the hypothesis that EQ-5D-5L could adequately discriminate between patients with metastatic disease and early-stage disease; secondary analyses addressed utility values between women in breast-cancer associated health states. A suggested minimally important difference (MID) for the Canadian scoring of the EQ-5D-5L is 0.037; we evaluated whether the lower bound of the 95% confidence interval (95%CI) exceeded this value. In terms of convergent/divergent validity, the primary analysis tested the hypothesis that EQ-5D-5L mean utility values for each health state (HS) would be at least moderately correlated with ESAS total symptom distress score (SDS) (|r|&gt;0.30) using Wilcoxon rank-sum tests and Spearman’s correlation tests. Construct validity was considered as acceptable if the hypotheses of the primary analysis are satisfied.
Results: We recruited 549 women, 406 (74%) with early-stage disease and 143 (26%) with metastatic disease (HS5), with a mean age of 57 (SD 12); 412 (75%) had been diagnosed with breast cancer in the 7 years prior to recruitment and were receiving active treatment for their cancer. The mean utility value for early-stage breast cancer was 0.84 (95% CI 0.83-0.86) and for metastatic breast cancer (0.78, 95% CI 0.76-0.81). This difference was 0.060 (95% CI 0.036 to 0.085, p&lt; 0.001) with the lower bound of the confidence interval slightly less than the prespecified MID (0.037). There was no significant difference between the mean utility value for women in the first year after primary breast cancer diagnosis (HS1), and women in their second to fifth year after a primary breast cancer treated with curative intent (HS3) or between women in HS1 and women in their sixth and following years after a primary breast cancer treated with curative intent (HS4). EQ-5D-5L also did not discriminate between women in HS3 and HS4. For convergent/divergent validity, there was a negative correlation between utility values and ESAS physical, emotional and total SDSs. EQ-5D-5L and ESAS total SDSs correlation coefficients were higher than 0.30 for all health states.
Conclusion: EQ-5D-5L met criteria for convergent/divergent validity in women with breast cancer. The tests for discriminant validity were equivocal, suggesting more research is needed for assessing construct validity with a larger sample size.
Table 1. EQ-5D-5L Utility Values. N= number; Std Dev= standard deviation; IQR= interquartile range; CI= confidence interval
Citation Format: Sofia Torres, Maureen Trudeau, Geoffrey Liu, Nicholas Mitsakakis, Ahmed Bayoumi. Validity of EQ-5D-5L for women with breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-05-43.