RESUMO
BACKGROUND AND OBJECTIVE: The EPIC (Expanded Prostate Cancer Index Composite) is a specific questionnaire for patients with prostate cancer designed to evaluate the impact of treatments on their quality of life. It contains 50 items divided in 4 summaries: urinary, intestinal, sexual and hormonal. The objective was to adapt the EPIC to Spanish and to evaluate its metric characteristics. METHOD: The method followed for the adaptation included translation and back-translation. The metric characteristics were evaluated in 50 patients from each treatment -prostatectomy, brachytherapy and external radiotherapy-, all of whom were administered the EPIC, SF-36 and FACT (Functional Assessment of Cancer Therapy) pre and post intervention. Reliability was evaluated with the Cronbach alpha coefficient. Construct validity was assessed by means of correlations between subscales of the EPIC and questionnaires, and comparing the patients with and without hormonal therapy (T-test). In order to value sensitivity to change, the standardized effect size was calculated after the intervention. RESULTS: The Cronbach's alpha of the EPIC summaries was high (0.66-0.89). The correlations between the EPIC and the FACT were near or higher than 0.4. Differences were found in the hormonal and sexual summaries between the patients with and without hormonal therapy (p<0.01). The standardized effect size was large (>0.8) in the urinary (3 groups) and sexual (group of prostatectomy) summary, and moderate in the intestinal summary (0.6 and 0.7) for the 2 groups of radiotherapy. CONCLUSIONS: The Spanish version of the EPIC is reliable, valid and presents an excellent sensitivity to change, being a useful tool to compare the impact in the quality of life of the 3 treatments.