Responsiveness of disease-specific and generic utility instruments in prostate cancer patients

Preferences (utilities) for health outcomes have an important role in decisions about prostate cancer screening and treatment. The responsiveness of utility instruments has not been evaluated.

Prostate cancer outpatients from the Princess Margaret Hospital, Toronto (n = 248) were allocated into three cohorts: N - newly diagnosed and treated; M - metastatic disease; O - all others.

We measured quality of life at 3 points within 12 months using 3 disease-specific utility instruments (Patient Oriented Prostate Utility Scales), 3 generic utility instruments (Health Utilities Index, EQ-5D, Quality of Well-Being Scale), and 3 profile scales (PORPUS-P profile, Prostate Cancer Index, QLQ-C-30). Responsiveness was assessed using measures of internal responsiveness (standardized effect size, standardized response mean) and external responsiveness (receiver operator curve analysis, mixed model regression).

Cohort N patients showed post-treatment declines followed by improvement in global health and functional status. Disease specific instruments detected moderate (0.4-1.3) decrements followed by small increments (0.1-0.4) in standardized effect size and standardized response mean. Most instruments detected change using external responsiveness measures (all cohorts).

Disease-specific utility instruments appeared to be more responsive than generic instruments. Use of generic instruments should be supplemented with a responsive disease-specific instrument, particularly for applications in early prostate cancer.