Eliciting Social Preference Weights for Functional Assessment of Cancer Therapy-Lung Health States

Background: The Functional Assessment of Cancer Therapy-Lung (FACT-L) is a multidimensional measure of quality of life developed for use in the evaluation of interventions in lung cancer. Objective: To develop a set of utility weights that could be used to convert FACT-L into a single index capable of being used in the economic analysis of clinical trial data. Method: A core set of FACT-L items were valued in two versions of a 14-page postal survey of over 400 members of the UK general population. Respondents valued hypothetical FACT-L health states using a scale from 0 to 100 (worst to best health state). Respondents also valued their own health using the standard form of the EuroQol EQ-5D. Data were entered into an ordinary least squares regression model. Results: Item weights estimated in regression analysis yielded values for 10 items from the FACT-L. The summary index based on this selected set of FACT-L items has a maximum value of 0.703 and a minimum value of 0.111. Conclusion: This study demonstrates a practical method of converting a standard condition-specific measure into a form that has the requisite properties to legitimise its use in cost-utility analysis. The methodology used here is not unique to FACT-L and might be considered appropriate for use in converting similar instruments.