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Skolarus TA, Dunn RL, Sanda MG, Chang P, Greenfield TK, Litwin MS, Wei JT, PROSTQA Consortium. Minimally important difference for the Expanded Prostate Cancer Index Composite Short Form. Urology. 2015 Jan 1; 85(1):101-5.
OBJECTIVE: To establish a score threshold that constitutes a clinically relevant change for each domain of the Expanded Prostate Cancer Index Composite (EPIC) Short Form (EPIC-26). Although its use in clinical practice and clinical trials has increased worldwide, the clinical interpretation of this 26-item disease-specific patient-reported quality of life questionnaire for men with localized prostate cancer would be facilitated by characterization of score thresholds for clinically relevant change (the minimally important differences [MIDs]). METHODS: We used distribution- and anchor-based approaches to establish the MID range for each EPIC-26 domain (urinary, sexual, bowel, and vitality/hormonal) based on a prospective multi-institutional cohort of 1201 men treated for prostate cancer between 2003 and 2006 and followed up for 3 years after treatment. For the anchor-based approach, we compared within-subject and between-subject score changes for each domain to an external "anchor" measure of overall cancer treatment satisfaction. RESULTS: We found the bowel and vitality/hormonal domains to have the lowest MID range (a 4-6 point change should be considered clinically relevant), whereas the sexual domain had the greatest MID values (10-12). Urinary incontinence appeared to have a greater MID range (6-9) than the urinary irritation/obstruction domain (5-7). CONCLUSION: Using 2 independent approaches, we established the MIDs for each EPIC-26 domain. A definition of these MID values is essential for the researcher or clinician to understand when changes in symptom burden among prostate cancer survivors are clinically relevant.