Mapping QLQ-C30 Onto EQ-5D-5L and SF-6D-V2 in Patients With Colorectal and Breast Cancer From a Developing Country

Objectives: Many studies have mapped the QLQ-C30 onto the EQ-5D or the SF-6D utilities; however, these studies were limited to developed countries. So this study aimed to map QLQ-C30 onto the SF-6D version 2 (SF-6D-v2) and EQ-5D-5L using the data collected from patients with colorectal and breast cancer in a developing country. Methods: A cross-sectional data set of 668 inpatient and outpatient patients with cancer was gathered from 4 teaching hospitals of cancer treatment in Tehran and Yazd from May 2017 to November 2018. The ordinary least squares (OLS) and censored least absolute deviations (CLAD) models were applied to estimate the utility values of both EQ-5D-5L and SF-6D-V2 using the QLQ-C30. Predicted R-2 and adjusted R-2 were used to evaluate the goodness of fit of the models. Moreover, the predictive performance of 2 models was assessed through estimating the mean absolute error (MAE), root mean square error (RMSE), intraclass correlation coefficients (ICC), and Spearman's rho. The 10-fold cross-validation method was also applied for validation of models. Results: The OLS Model E4 was the best-performing model for EQ-5D-5L (Adj R-2 = 71.7%, Pred R-2 = 71.15%, MAE = 0.0770, RMSE = 0.1026), and the OLS Model S4 performed best for SF-6D-V2 (Adj R-2 = 74.64%, Pred R-2 = 73.86%, MAE = 0.0465, RMSE = 0.0621). Conclusion: The OLS Model E4 for EQ-5D-5L and the OLS Model S4 for SF-6D-V2 were the best models for policy makers to have more accurate evaluation of the healthcare interventions when the data are gathered through non-preference-based instruments.