Abstract
The objective of this study was to assess the psychometric properties of the Thai version of the European
Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30)
version 3.0. The questionnaire was completed by 310 cancer patients during their follow-up at 2 teaching
hospital oncology clinics. About 70% of participants had advanced stage of cancer and 72% had been
receiving chemotherapy. Cronbach’s a coefficients of the six scales were above 0.7, except for cognitive and
social function scales. All test–retest reliability coefficients were high. Multitrait scaling analysis showed
that all item-scale correlation coefficients met the standards of convergent and discriminant validity. Most
scales and items could discriminate between subgroups of patients with different clinical status assessed
with the Eastern Cooperative Oncology Group (ECOG) scale. The results suggested that the EORTC
QLQ-C30 and the Functional Assessment of Cancer Therapy – General (FACT-G) measured different
aspects of quality of life and should be independently used. Testing psychometric properties of the EORTC
QLQ-C30 in heterogeneous diagnostic group yield similar results as found in homogeneous group. These
results support that the EORTC QLQ-C30 (version 3.0) has proven to be a reliable and valid measure of
the quality of life in Thai patients with various types of cancer.