[The critical appraisal of QOL questionnaire for prostate cancer patients]

Prostate cancer is a common malignancy that affects Japanese elderly men. Its incidence is increasing, recently, and its treatments are various. The measurement of quality of life (QOL) has become important for the evaluation of and selection of treatments. In Japan, however, there is no standard way of measuring QOL for prostate cancer patients, except the Japanese version of the EORTC QOL questionnaire for prostate cancer patients. We examined the validity and feasibility of this translated EORTC QOL questionnaire for prostate cancer patients.

Sixty-nine prostate cancer patients who were under treatment in 4 hospitals were selected for this study. We applied the content validity, the factorial validity which was analyzed by the oblique principal component cluster analysis, the internal consistency analyzed by the alpha coefficient of Cronbach, the convergent validity which was used GHQ, IPSS and PS as external measures, and the feasibility.

This questionnaire showed good internal consistency, as the alpha coefficient was 0.61 to 0.90 in all domains, except for sex life, which was the lowest. This questionnaire was classified into 7 clusters by the oblique principal component cluster analysis. Consequently, the factorial validity was good, except for items regarding sex life. As domains correlate well with external measures except in sex life, the convergent validity was good. It was suggested that only two items were not acceptable in regard to the content validity and the feasibility, and that the translation into Japanese of 2 items was inadequate.

Our study suggests that the Japanese version of the EORTC QOL questionnaire for prostate cancer patients demands improvement for the practical employment in clinical trials, as there is a problem of translation and feasibility.