THE DANGER OF APPLYING GROUP-LEVEL UTILITIES IN DECISION ANALYSES OF THE TREATMENT OF LOCALIZED PROSTATE-CANCER IN INDIVIDUAL PATIENTS

The optimal management strategy for men who have localized prostate ca ncer remains controversial. This study examines the extent to which su ggested treatment based on the perspective of a group or society agree s with that derived from individual patients' preferences. A previousl y published decision analysis for localized prostate cancer was used t o suggest the treatment that maximized quality-adjusted life expectanc y. Two treatment recommendations were obtained for each patient: the f irst (group-level) was derived using the mean utilities of the cohort; the second (individual-level) used his own set of utilities. Group-le vel utilities misrepresented 25-48% of individuals' preferences depend ing on the grade of tumor modeled. The best kappa measure achieved bet ween group and individual preferences was 0.11. The average quality-ad justed life years lost due to misrepresentation of preference was as h igh as 1.7 quality-adjusted life years. Use of aggregated utilities in a group-level decision analysis can ignore the substantial variabilit y at the individual level. Caution is needed when applying a group-lev el recommendation to the treatment of localized prostate cancer in an individual patient.