New reference values for cancer patients' quality of life
Researchers and practitioners around the globe frequently use the EORTC questionnaire to measure self-reported quality of life in cancer patients. For the first time, researchers from Charité - Universitätsmedizin Berlin report quality of life normative data for the general populations of 15 countries. This data allows for a more meaningful interpretation of questionnaire scores and provides information on regional differences in quality of life. The results of this study have now been published in the European Journal of Cancer.
Have you felt any pain over the past week? Have you felt tired? Have you been worried?
Across the globe, questions such as these are used to measure the health-related quality of life of cancer patients. To determine how patients feel before, during or after cancer treatment, clinicians and researchers use questionnaires such as the QLQ-C30 that was developed by the European Organisation for Research and Treatment of Cancer (EORTC) over 25 years ago. It is one of the most widely used medical questionnaires, frequently applied as part of clinical trials but also as part of clinical routine.
Results obtained using this questionnaire can provide information on the effectiveness of a particular treatment or serve as evidence either in favor of or against the approval of a new drug.
However, quality of life data are of limited value in the absence of normative values, i.e., data obtained from the general population. Such norm data allow for a more sensible interpretation of patient-reported data. An international group of researchers has now successfully determined normative QLQ-C30 data as part of a large-scale study. Using online surveys, the panel research company GfK collected quality of life data from more than 15,000 persons from the general population across 11 EU countries, as well as Russia, Turkey, Canada and the United States. Data from the 11 EU countries was further used to establish the European QLQ-C30 Norm.
"The newly established norm values allow for a more precise interpretation of patient-reported quality of life data", explains study lead Dr. Sandra Nolte from Charité's Health Outcomes Research Unit of the Medical Department, Division of Psychosomatic Medicine. She adds, "Norm values already existed for a number of countries. However, these were usually determined using different survey methodologies, meaning that they were not suitable for use in multinational studies. For the first time, we applied consistent data collection methods across all 15 included countries, facilitating valid intra- and especially inter-country comparisons and QLQ-C30 score interpretation. This will be of benefit to researchers across the globe and, ultimately, to cancer patients."
National differences in quality of life scores came as a surprise and constituted an interesting secondary finding. While Germans reported mid-level quality of life scores, the highest scores were reported by respondents from Austria and the Netherlands. In contrast, Poland, Russia, Turkey, the United Kingdom and the United States scored significantly lower across many health-related quality of life domains. Compared to respondents from Austria or the Netherlands, respondents from these countries rated their physical and emotional health as worse and reported more fatigue and financial difficulties.
"These results demonstrate the importance of using the relevant national norms when conducting country-specific studies," says Dr. Nolte. She adds, "After all, when a cancer patient reports feeling fatigued, it makes a difference whether they are from Russia or from Spain—in Russia, the general population reports significantly higher levels of fatigue than in Spain. We now have norm scores for a total of 15 individual countries. This enables us to make country-specific as well as international comparisons of cancer patients' self-reported quality of life."
The EORTC Quality of Life Questionnaire
The EORTC Quality of Life Questionnaire Core 30 (QLQ-C30) comprises 30 questions that are used to assess the quality of life of cancer patients. It includes questions on the respondent's physical, cognitive, emotional and role functioning, as well as their general health and symptoms such as pain, fatigue, nausea and shortness of breath. The QLQ-C30 can be administered as either a paper-based or an electronic questionnaire. It is also available as a computer-adaptive version (EORTC CAT Core), which adapts the test in such way that only items are shown that are relevant to the individual patient. The EORTC CAT Core is readily available for use and already incorporates the new general population norm data.
G. Liegl et al. Establishing the European Norm for the health-related quality of life domains of the computer-adaptive test EORTC CAT Core, European Journal of Cancer (2018). DOI: 10.1016/j.ejca.2018.11.023