The impact of pelvic magnetic resonance imaging on risk stratification in patients with localized prostate cancer.

Abstract

130 Background: We aimed to determine the impact of multiparametric magnetic resonance imaging (MRI) of the prostate on established risk stratification criteria in patients with clinically localized adenocarcinoma of the prostate (ACP). Methods: We included patients who had undergone multiparametric prostate MRI at our institution as part of their initial workup for ACP. Traditional risk stratification criteria (prostate specific antigen, clinical T stage, biopsy Gleason score) were recorded, and the initial National Comprehensive Cancer Network (NCCN) risk group was calculated. The NCCN risk group was then recalculated incorporating MRI findings. The impact of MRI findings on changes in risk group classification was evaluated using the Stuart-Maxwell test for marginal homogeneity. Results: Of 71 patients analyzed, 11 (15.5%), 39 (54.9%), and 21 (29.6%) had low, intermediate, and high risk disease, respectively. MRI findings led to risk group upstaging in 12 cases (16.9%). The highest yield was demonstrated in patients with intermediate-risk disease, in whom MRI led to upstaging in 25.6% of patients. The Stuart-Maxwell test demonstrated a significant difference between pre-MRI and post-MRI risk group classifications (p <0.01) for the entire cohort. Pre-MRI and post-MRI risk groups for all patients are shown in the table, with off-diagonal elements representing risk group changes. MRI findings resulted in clearly documented changes in the treatment strategy for 5 patients (7.0%), including addition of androgen deprivation therapy in 2 patients, elimination of definitive therapy in 2 patients determined to have metastatic disease, and elimination of a brachytherapy boost in one patient. Conclusions: In our cohort of patients with clinically localized ACP, MRI findings often led to significant changes in risk stratification and treatment. Our findings support the routine use of MRI in the workup of patients with clinically localized ACP, particularly those with intermediate risk disease . [Table: see text]