Purpose: Understanding men’s preferences for prostate cancer treatment is central to achieving the promise of shared decision-making in urologic oncology. Our objective was to evaluate the reliability and construct validity of a clinically relevant and comprehensive measure of men’s preferences for prostate cancer treatment.
Methods: A cross-sectional sample of men newly or previously diagnosed with localized prostate cancer (n=393) completed the Values Insight and Balance Evaluation scales (VIBEs), a Time Trade Off (TTO) utilities measure, and demographic and clinical questions. VIBEs is a 46-item measure of prostate cancer treatment preferences developed from an explicitly derived conceptual framework and interviews with prostate cancer patients, their spouses, and relevant clinicians. We determined internal consistency using Cronbach’s alpha, and conducted confirmatory factor analysis (CFA) using a robust maximum likelihood approach for non-normal distributions. We also calculated Pearson correlations between VIBEs subscale scores and utilities elicited using the TTO and conducted a known-groups analysis of the VIBEs comparing active treatment and watchful waiting.
Results: Participants ranged in age from 40 to 89. Most were Caucasian (84%), married or living with a partner (61%), and had received active treatment (e.g., surgery, radiation) (78%). Internal consistency coefficients ranged from 0.71 to 0.94, with most above 0.80. CFA revealed that eleven VIBEs subscales fit the data well based on a non-significant chi-square statistic (p=0.13), an RMSE<0.05 (RMSE=0.03), and a CFI>0.95 (CFI=0.99). Standardized estimates for subscale domains ranged from 0.48 to 0.88. There were significant correlations between TTO subscales of urinary, sexual, and bowel function and corresponding VIBEs subscales (p =0.0021-0.0285). In a known-group analysis of active treatment versus watchful waiting, the active treatment group had significantly higher scores on the VIBEs Survival subscale than the watchful waiting group (p=0.0007).
Conclusions: Eleven domains represent a strong conceptual structure for the interpretation of VIBEs subscale scores in this population. The domains include general concerns (e.g., responsibilities, self-image) as well as prostate cancer specific considerations (e.g., urologic function). While extensive measurement of patient preferences is not required for all medical decisions, a full assessment of patient values is appropriate for prostate cancer where choices are complex and will have long lasting consequences. Evidence supports the VIBEs as a reliable and conceptually strong measure of preferences with potential to improve shared decision making.