Objective: Recent years have shown an increase in the use of
questionnaires measuring health-related quality of life to verify the
quality of treatment in the field of oncology. An often used
cancer-specific questionnaire is the “Quality of Life Core
Questionnaire of the European Organization for the Research and Treatment
of Cancer” (EORTC QLQ-C30). The purpose of this study is to analyze
the psychometric properties of the EORTC QLQ-C30 (version 1) in order to
determine the feasibility and appropriateness for its use in inpatient
cancer rehabilitation in Germany with heterogeneous diagnoses.
Methods: The questionnaire was administrated to a sample of
972 cancer patients at the beginning of treatment and to 892 patients
after treatment. Besides descriptive analysis, the statistical analyses
include confirmatory analysis and the multitrait/multimethod approach
to test the questionnaire's postulated scale structure (factorial
validity) and its reliability (internal consistencies). The analysis also
includes a comparison of responsiveness indices (effect size, reliable
change index) to test the sensitivity of the instrument.
Results: The EORTC QLQ-C30 showed satisfactory levels of
reliability and sensitivity, but the postulated scale structure could not
be confirmed. The results illustrate that the varimax-rotated solution of
a principal component analysis does not confirm the scale structure
postulated by the authors. Correspondingly, the selected fit indices
within the scope of the confirmatory factor analysis do not show
satisfactory results either.
Significance of results: We therefore consider version 1 of
the EORTC QLQ-C30 to be only limitedly useful for the routine assessment
of changes in the quality of life of cancer patients in inpatient
rehabilitation in Germany, especially because of the instrument's
length and possible redundancies. For this reason, a scoring procedure
limited to a subset of items is suggested, revealing satisfactory to good
psychometric indices. However, further psychometric tests are necessary,
especially with regard to validity and sensitivity.