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Tuesday, 17 October 2006


Vibha Bhatnagar, MD, MPH, University of California San Diego and VA San Diego Healthcare System, San Diego, CA, Dominick Frosch, PhD, UCLA, Los Angeles, CA, Steven Tally, PhD, University of California San Diego, La Jolla, CA, and Robert M. Kaplan, PhD, University of California Los Angeles, Los Angeles, CA.

Purpose: To evaluate an Internet-based decision tool presenting a prostate cancer disease trajectory and the decision to choose prostate specific antigen (PSA) screening for prostate cancer. This tool included a visual analog scale (VAS) and a time trade-off (TTO) exercise, designed to help men determine their preferences for PSA screening.

Methods: As part of an Internet-based randomized trial comparing decision tools for PSA screening, 152 men over the age of 50 and scheduled for a physical exam, reviewed a prostate cancer disease trajectory model for moderately differentiated localized prostate cancer, with and without treatment (surgery or radiation). Participants rated their expected quality of life should they be diagnosed and treated for localized prostate cancer after PSA screening using a VAS (0 to 100%). They were then asked how many years they were willing to trade to be free of expected symptoms resulting from treatment for early prostate cancer using a 10-year TTO exercise. Subsequent PSA screening was determined through a self-report questionnaire completed after their exam.

Results: Of the 77 men who completed the VAS and TTO exercise, and follow-up questionnaires, 60 choose PSA screening. There were no baseline differences between those who did and did not get PSA screening (mean age 58 + 6 vs. 59 + 5 years, 77% vs. 78% married, 81% vs. 84% Caucasian, and 97% vs. 95% had some college education). After exclusion of 7 men with inconsistent VAS and TTO results, there was a strong direct relationship between VAS and TTO scores (regression model adjusted R2=0.32, p<0.001). For a ten-unit increase in VAS, the odds ratio of choosing a PSA test was 1.51 (95% CI 1.04 to 2.18); for each 0.5 year traded in order to be free of symptoms the odds ratio was 0.67 (0.48 to 0.94). Adjustment for prostate cancer knowledge or baseline factors (age, ethnicity etc.) did not alter these findings.

Conclusion: VAS and TTO decision tools in the context of a disease trajectory model appear to be good measures of patient preference; patients with lower ratings for symptoms associated with prostate cancer treatment were more likely to refuse the PSA test. However, low completion rates suggest that these tools need to be developed further in order for patients to use them independently over the Internet.

See more of Poster Session III
See more of The 28th Annual Meeting of the Society for Medical Decision Making (October 15-18, 2006)