Abstract
Purpose
To develop a mapping algorithm for a conversion of the EORTC QLQ-C30 and EORTC QLQ BR-23 into the EQ-5D-derived utilities in metastatic breast cancer (MBC) patients.
Methods
We enrolled 199 patients with MBC from four leading Korean hospitals in 2009. EQ-5D utility, cancer-specific (QLQ-C30) and breast cancer-specific quality of life data (QLQ-BR23) and selected clinical and demographic information were collected from the study participants. Ordinary least squares regression models were used to model the EQ-5D using QLQ-C30 and QLQ-BR23 scale scores. To select the best model specification, six different sets of explanatory variables were compared.
Result
Regression analysis with the multiitem scale scores of QLQ-C30 was the best-performing model, explaining for 48.7% of the observed EQ-5D variation. Its mean absolute error between the observed and predicted EQ-5D utilities (0.092) and relative prediction error (2.784%) was among the smallest. Also, this mapping model showed the least systematic errors according to disease severity.
Conclusions
The mapping algorithms developed have good predictive validity, and therefore, they enable researchers to translate cancer-specific health-related quality of life measures to the preference-adjusted health status of MBC patients.
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Abbreviations
- CUA:
-
Cost-utility analysis.
- ECOG:
-
Eastern cooperative oncology group
- EORTC QLQ-BR23 (or QLQ-BR23):
-
European Organization for Research and Treatment of Cancer quality of life questionnaire breast cancer-23
- EORTC QLQ-C30 (or QLQ-C 30):
-
European Organization for Research and Treatment of Cancer quality of life questionnaire core-30
- EQ-VAS:
-
EQ-5D visual analogue scale
- ISPOR:
-
International society for pharmacoeconomics and outcomes research
- MBC:
-
Metastatic breast cancer
- NHI:
-
National health insurance
- OLS:
-
Ordinary least squares
- QALYs:
-
Quality-adjusted life years
- QOL:
-
Quality of life
- RPE:
-
Relative prediction error
- VIF:
-
Variance inflation factor
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Acknowledgments
This study was supported by an unrestricted grant from Pfizer Pharmaceuticals Korea Limited.
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Appendices
Appendix 1: Technical summary: principles of scoring of QLQ-C30
This was taken from the EORTC QLQ-C30 Scoring Manual [12].
-
1.
Calculate raw score
If items I 1, I 2,…I n are included in a scale, then the raw score of a scale is calculated as follows:
-
2.
Linear transformation
Apply the linear transformation to 0–100 to obtain the score S,
Functional scales: score = {1−(RS−1)/range} × 100
Symptom scales/items: score = {(RS−1)/range} × 100
Global health status/QOL: score = {(RS−1)/range} × 100
Range is the difference between the maximum possible value of RS and the minimum possible value. The QLQ-C30 has been designed so that all the items in any scale take the same range of values. Therefore, the range of RS equals the range of the item values. Most items are scored 1–4, giving a range = 3. The exceptions are the items contributing to the global health status/QOL, which are 7-point questions with a range = 6, and the initial yes/no item on the earlier versions of the QLQ-C30, which have range = 1.
Appendix 2
See Table 6.
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Kim, Ej., Ko, SK. & Kang, HY. Mapping the cancer-specific EORTC QLQ-C30 and EORTC QLQ-BR23 to the generic EQ-5D in metastatic breast cancer patients. Qual Life Res 21, 1193–1203 (2012). https://doi.org/10.1007/s11136-011-0037-y
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DOI: https://doi.org/10.1007/s11136-011-0037-y