Abstract
BackgroundNo official German translation exists for the 50-item Expanded Prostate Cancer Index Composite (EPIC), and no minimal important difference (MID) has been established yet. The aim of the study was to translate and validate a German version of the EPIC with cultural adaptation to the different German speaking countries and to establish the MID.MethodsWe translated and culturally adapted the EPIC into German. For validation, we included a consecutive subsample of 92 patients with localized prostate cancer undergoing radical prostatectomy who participated the Prostate Cancer Outcomes Cohort. Baseline and follow-up assessments took place before and six weeks after prostatectomy in 2010 and 2011.We assessed the EPIC, EORTC QLQ-PR25, Feeling Thermometer, SF-36 and a global rating of health state change variable. We calculated the internal consistency, test-retest reliability, construct validity, responsiveness and MID.ResultsFor most EPIC domains and subscales, our a priori defined criteria for reliability were fulfilled (construct reliability: Cronbach’s alpha 0.7–0.9; test-retest reliability: intraclass-correlation coefficient ≥ 0.7). Cross-sectional and longitudinal correlations between EPIC and EORTC QLQ-PR25 domains ranged from 0.14–0.79, and 0.06–0.5 and 0.08–0.72 for Feeling Thermometer and SF-36, respectively. We established MID values of 10, 4, 12, and 6 for the urinary, bowel, sexual and hormonal domain.ConclusionThe German version of the EPIC is reliable, responsive and valid to measure HRQL in prostate cancer patients and is now available in German language. With the suggested MID we provide interpretation to what extent changes in HRQL are clinically relevant for patients. Hence, study results are of interest beyond German speaking countries.
Highlights
No official German translation exists for the 50-item Expanded Prostate Cancer Index Composite (EPIC), and no minimal important difference (MID) has been established yet
A well-established MID of an instrument is important for clinicians and researchers because it shows whether a specific change score derived from assessments before and after an intervention reflects a difference that is relevant for the patient
This first version was pretested in cognitive debriefings in five prostate cancer patients who agreed on a second German version
Summary
No official German translation exists for the 50-item Expanded Prostate Cancer Index Composite (EPIC), and no minimal important difference (MID) has been established yet. A well-established MID of an instrument is important for clinicians and researchers because it shows whether a specific change score derived from assessments before and after an intervention reflects a difference that is relevant for the patient. One of the most established and frequently used instrument focussing on diseasespecific aspects of prostate cancer and its therapies is the 50-item Expanded Prostate Cancer Index Composite (EPIC) [5]. Compared to the other frequently used instrument, the European Organization for the Research and Treatment of Cancer Quality of Life Questionnaire– Prostate 25 (EORTC QLQ-PR25) tool [13], the EPIC seems to provide a better balanced performance to assess more in depths the various side effects independent of treatment modality chosen
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