Mapping the EORTC QLQ C-30 onto the EQ-5D instrument: the potential to estimate QALYs without generic preference data.

OBJECTIVES The aim of this article is to map the European Organization for Research and Treatment of Cancer (EORTC) QLQ C-30 onto the EQ-5D measure to enable the estimation of health state values based on the EORTC QLQ C-30 data. The EORTC QLQ C-30 is of interest because it is the most commonly used instrument to measure the quality of life of cancer patients. METHODS Regression analysis is used to establish the relationship between the two instruments. The performance of the model is assessed in terms of how well the responses to the EORTC QLQ C-30 predict the EQ-5D responses for a separate data set. RESULTS The results showed that the model explaining EQ-5D values predicted well. All of the actual values were within the 95% confidence intervals of the predicted values. More importantly, predicted difference in quality-adjusted life-years (QALYs) between the arms of the trial was almost identical to the actual difference. CONCLUSION There is potential to estimate EQ-5D values using responses to the disease-specific EORTC QLQ C-30 measure of quality of life. Such potential implies that in studies that do not include disease-specific measures, it might still be possible to estimate QALYs.