Comparison of two quality-of-life instruments for cancer patients: The functional assessment of cancer therapy-general and the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-C30

Purpose: To compare two quality-of-life (QOL) questionnaires for cancer pat ients, the European Organization for Research and Treatment of Cancer Quali ty of Life Questionnaire-C30 (EORTC QLQ-C30) and the Functional Assessment of Cancer Therapy-General (Fact-G), on the basis of empirical data. Patients and Methods: Two hundred forty-four patients with a diagnosis of b reast cancer or Hodgkin's disease completed both the EORTC QLQ-C30 and the FACT-G (German language version) during the same session. Questionnaire dat a were analyzed on a subscale basis using correlation analysis, canonical c orrelation, and multiple linear regression. Results: Correlations between corresponding subscales of the FACT-G and the EORTC QLQ-C30 ranged from r = .14 for the social domain (very poor agreeme nt) to r = .66 for the physical domain (good agreement), with r valuer for the other domains lying between these extremes. Canonical correlation analy sis for the two sets of subscales revealed that overall agreement between t he two instruments was only moderate (first canonical correlation coefficie nt r = .85, but overall redundancy less than 40%). Of the five FACT-G subsc ales, only one, physical well-being, was well represented by the EORTC QLQ- C30 subscales (multiple linear regression, R-2 = .67), Only three of; eight EORTC QLQ-C30 subscales (physical functioning, global QOL, general symptom s) were represented fairly well by FACT-G subscales (R-2 = .43 ta .60). The lowest R-2 values (< .15; ie, virtually no representation by the other ins trument) were found for the FACT-G social well-being and relation with doct ors and EORTC QLQ-C30 cognitive functioning subscales, Conclusion: For the sample investigated, the EORTC QLQ-C30 and the FACT-G w ere found to measure markedly different aspects of QOL, despite considerabl e overlap. Replicability provided, this implies that neither of the two QOL instruments can be replaced by the other and that a direct comparison of r esults obtained with the two instruments is not possible. (C) 1999 by Ameri can Society of Clinical Oncology.