Health state utility scores in advanced non-small cell lung cancer

Summary

Background

The aim of the study was to capture societal utility scores for health state descriptions of advanced, metastatic non-small cell lung cancer (NSCLC), as well as determine disutility associated with specific disease symptoms.

Methods

NSCLC health states were produced based on an adaptation of existing health state descriptions for metastatic lung cancer. The health states were expanded to contrast disease state (responding disease and stable disease) and impact of specific severe symptoms (cough; dyspnoea; pain; or no additional severe symptoms). Interviews with five lung cancer clinicians were carried out to assess the content and face validity of the existing health states as descriptions specific to NSCLC. The interviews also sought to explore the impact of the disease symptoms of interest. The resulting health states were reviewed by two psychometric experts independently. The final health states were piloted in a conventional standard gamble interview which revealed no significant issues in interpretation or comprehension. In the main study, 101 members of the general public assessed their preference for each health state in a chained standard gamble (SG) interview and on a visual analogue scale (VAS) rating scale. All participants also completed the EQ-5D and a socio-demographic form.

Results

The study sample was a relatively good match to the characteristics of the general public in England and Wales. A mixed model analysis revealed that age, gender, and HRQL were not significant predictors of utility, but a treatment response and each of the disease symptoms were. When adjusted to match census data, stable disease with no additional symptoms had a utility value of 0.626. Health state values declined by 0.069 with the addition of pain; 0.050 for dyspnoea; or 0.046 for cough. A treatment response would result in a utility gain of 0.086.

Conclusions

Members of the general public showed a preference for responding disease over stable disease and a stable health state with no additional symptoms over a stable health state with one of the three common NSCLC symptoms: cough, dyspnoea, and pain. The study highlights the value that society places on the avoidance of severe symptoms that some people with NSCLC can experience.

Introduction

The therapeutic benefit of chemotherapy is usually considered in terms improved survival, quality of life and the associated toxicity profile. In non-small cell lung cancer (NSCLC) the symptom burden associated with the disease can be substantial, including fatigue, pain, cough and dyspnoea [1]. Modern palliative care can fail to adequately control these symptoms. Indeed relatively little is known about the specific burden of these symptoms [2]. The symptom burden can be difficult to treat and can fail to respond to palliative care [3]. The impact of symptoms in NSCLC could be measured in terms of their impact on health-related quality of life (HRQL).

Valid and reliable disease specific HRQL measures exist for assessing people with lung cancer including the EORTC QLQ-LC13 [4] and the FACT-L [5]. Such measures are able to record the impact of symptoms on HRQL and the benefits of a therapy to reduce symptoms. However these measures do not record how much value patients place in the avoidance of different symptoms. To capture this type of information it is necessary to use an HRQL measure in which the scores are weighted by preferences. Preference weighted measures benchmark changes in HRQL against other metrics of importance such as years of life or risk of immediate death. One advantage of preference-weighted measures is that it is clear how important any change in scores is. Another significant advantage is that HRQL is summarised as a single index anchored at 1 (full health) and 0 (dead) which can be used to weight survival as a metric in economic evaluations. Economic evaluations are often conducted to guide the efficient allocation of public resources and so should reflect the preferences of society [6].

Generic preference weighted measures exist such as the EQ-5D [7] and the Health Utilities Index [8]. However such generic measures may lack the sensitivity to reflect changes in symptom status of patients. Therefore to understand the value of symptom avoidance in NSCLC, the present study was designed to develop disease specific health state descriptions. These states described metastatic disease and included specific severe symptoms such as cough, dyspnoea and pain. The health states were then weighted in a valuation exercise. Analyses of these data were designed to indicate what the impact of specific symptoms is in the context of metastatic NSCLC.