Development and validation of the expanded prostate cancer index composite(EPIC) for comprehensive assessment of health-related quality of life in men with prostate cancer

Objectives. Health-related quality of life (HRQOL) is an increasingly impor tant endpoint in prostate cancer care. However, pivotal issues that are not fully assessed in existing HRQOL instruments include irritative urinary sy mptoms, hormonal symptoms, and multi-item scores quantifying bother between urinary, sexual, bowel, and hormonal domains, We sought to develop a novel instrument to facilitate more comprehensive assessment of prostate cancer- related HRQOL. Methods. Instrument development was based on advice from an expert panel an d prostate cancer patients, which led to expanding the 20-item University o f California-Los Angeles Prostate Cancer Index (UCLA-PCI) to the 50-item Ex panded Prostate Index Composite (EPIC). Summary and subscale scores were de rived by content and factor analyses. Reliability and validity were assesse d by test-retest correlation, Cronbach's alpha coefficient, interscale corr elation, and EPIC correlation with other validated instruments. Results. Test-retest reliability and internal consistency were high for EPI C urinary, bowel, sexual, and hormonal domain summary scores (each r greate r than or equal to0.80 and Cronbach's alpha greater than or equal to0.82) a nd for most domain-specific subscales. Correlations between function and bo ther subscales within domains were high (r > 0.60). Correlations between di fferent primary domains were consistently lower, indicating that these doma ins assess distinct HRQOL components. EPIC domains had weak to modest corre lations with the Medical Outcomes Study 12-item Short-Form Health Survey (S F-12), indicating rationale for their concurrent use. Moderate agreement wa s observed between EPIC domains relevant to the Functional Assessment of Ca ncer Therapy Prostate module (FACT-P) and the American Urological Associati on Symptom Index (AUA-SI), providing criterion validity without excessive o verlap. Conclusions. EPIC is a robust prostate cancer HRQOL instrument that complem ents prior instruments by measuring a broad spectrum of urinary, bowel, sex ual, and hormonal symptoms, thereby providing a unique tool for comprehensi ve assessment of HRQOL issues important in contemporary prostate cancer man agement. UROLOGY 56: 899-905, 2000. (C) 2000, Elsevier Science Inc.