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Patient Selection for Magnetic Resonance Imaging of Prostate Cancer

Background: Routine magnetic resonance (MR) imaging for local staging of prostate cancer is controversial, due to moderate staging performance. However, MR imaging may be beneficial in a subgroup of patients with clinically localized prostate cancer. Objective: To define the patient group in which local staging of prostate cancer using MR imaging is useful for treatment outcome. Methods: We used a decision analytic model based on data found in the literature to define the patient subgroup which may benefit from local staging with MR imaging. We applied the threshold approach to calculate the threshold where direct surgery and surgery after MR imaging (surgery–MR imaging threshold) result in equal utility. Additionally, we calculated the threshold where direct radiation and radiation after MR imaging (MR imaging–radiotherapy threshold) result in equal utility. Results: We found that the surgery–MR imaging threshold was at a probability of 45% of having stage ≧T3 disease. The MR imaging–radiotherapy threshold was at a prior probability of 81% of having stage ≧T3 disease. Conclusions: The application of the threshold approach indicated that MR imaging should be limited to patients with an intermediate–high risk of having stage T3 disease.