Portuguese version of the Expanded Prostate Cancer Index Composite for Clinical Practice (EPIC-CP): psychometric validation and prospective application for early functional outcomes at a single institution

Background The Expanded Prostate Index Composite for Clinical Practice (EPIC-CP) is a short version of the original EPIC, developed to facilitate the instrument's use in routine care. This study aimed to validate the EPIC-CP Portuguese version, and evaluate its role in presenting early functional outcomes of surgically treated prostate cancer patients at a Latin American referral center. Methods The EPIC-CP was self-administered prospectively and individually by all localized prostate cancer patients, before and after robotic-assisted radical prostatectomy, from March 2017 to June 2018 at a single institution. For validation, we used the Cronbach's alpha coefficient to evaluate internal consistency. The EPIC-CP domains were compared before surgery, and 6 months and 12 months after surgery. Statistical analyses were performed using the student's t test, and Wilcoxon and Friedman tests, with p values < 0.05 considered significant. Results One hundred and fifty two patients answered the EPIC-CP. The patients had a median age of 62.7 ([+ or -] 8.5) years and prostate specific antigen level of 6.3 ([+ or -] 4.6) ng/ml. The Cronbach's alpha varied from 0.75 to 0.77 for all domains with good internal consistency, except for the "vitality/hormonal" domain, which had a score of 0.35. The domain evolution for the preoperative and 6-month postoperative groups revealed that the domains related to urinary continence and bowel worsened, and were increased during the first 6 months; however, this variation had no obvious clinical implications, and the irritative symptoms improved. Regarding the sexual domain, the scores worsened, and also increased over the first 6 months. The results of the confirmatory factor analysis were robust, with an explained variance of 0.951 and covariance of 0.929. Conclusions The Portuguese version of the EPIC-CP is a reliable and valid questionnaire for postoperative patients, and very useful to improve the knowledge of the early functional outcomes of men treated for prostate cancer. Keywords: EPIC, Prostate cancer, Quality of life