The UCLA Prostate Cancer Index: Development, Reliability, and Validity of a Health-Related Quality of Life Measure

Abstract

OBJECTIVES: The need for accurate measures of health-related quality of life (HRQOL) in men treated for prostate cancer is of paramount importance because patients may survive for many years after their diagnosis. Hence, interest has increased in choosing treatments that optimize both the quality and quantity of life in patients with this disease. This study sought to develop and evaluate a self-administered, multiitem, disease-specific instrument to capture the health concerns central to the quality of life of men treated for early stage prostate cancer. METHODS: After focus group analysis and pilot testing, the instrument was tested with a large retrospective, cross-sectional survey. Exploratory factor analysis and multitrait scaling analysis were used to facilitate the formation of six scales containing 20 disease-targeted items that address impairment in the urinary, bowel, and sexual domains. The psychometric properties of the new scales were assessed by measuring test-retest reliability, internal consistency reliability, and construct validity. Performance on the new scales was compared with scores on other established cancer-related health-related quality of life instruments. Two hundred fifty-five long-term survivors of prostate cancer treatment and 273 age-matched and ZIP code-matched comparison subjects without prostate cancer from a large managed care population in California were studied. Mean age was 72.7 years. In addition to the new scales, the RAND 36-Item Health Survey (SF-36) was used as a generic core measure, and a cancer-related health-related quality of life instrument (the Cancer Rehabilitation System-Short Form) was used to provide construct validity. RESULTS: For the new scales, test-retest reliability ranged from 0.66 to 0.93, and internal consistency ranged from 0.65 to 0.93. Disease-targeted measures of function and bother in the three domains correlated substantially with one another. Scale scores correlated well with related, established scales. Men undergoing prostatectomy or pelvic irradiation demonstrated the expected differences in performance on the disease-specific health-related quality of life scales when compared with each other or with comparison subjects. Age was inversely related to sexual and bowel function. CONCLUSIONS: The UCLA Prostate Cancer Index performed well in this population of older men with and without prostate cancer. It demonstrated good psychometric properties and appeared to be well understood and easily completed. The high response among patients suggests that these men especially are interested in addressing both the general and disease-specific concerns that impact their daily quality of life.