MRI-based prostate specific antigen density predicts Gleason score upgrade in an active surveillance cohort.

107 Background: Elevated prostate specific antigen density (PSAD) based on transrectal ultrasound (TRUS) measurements has been shown to be strongly associated with clinically significant disease and to predict progression on active surveillance for men with low stage/grade disease. We hypothesize that elevated MRI PSAD is similarly associated with increased risk of progression on subsequent biopsy. Methods: Patients with Gleason grade 3+3 on diagnostic transrectal ultrasound-guided biopsy who were managed with active surveillance and underwent at least one additional biopsy were included. Patients who underwent MRI greater than 6 months after diagnosis were excluded. Summary statistics were generated for demographic and clinical characteristics. MRI PSAD was calculated using prostate volume on MRI and PSA temporally closest to the MRI. Multivariable logistics regression models were used to evaluate the association between MRI PSAD and predictors of upgrade on serial biopsy. Results: 166 patients were included in the study. Of these patients, 74 of them were upgraded to Gleason grade ≥7 on follow up biopsy. TRUS volume was noted be strongly correlated with MRI prostate volume (Pearson’s r=0.82, p<0.01). MRI PSAD 0.15-0.225 ng/ccl and ≥0.0225 ng/cc were significantly associated with upgrade to Gleason grade 7 compared to MRI PSAD <0.075 ng/ml/ml after controlling for age and time since diagnosis. MRI PSAD less than 0.15 was not associated with upgrade on follow up biopsy (in any patient, if so, state that no one with a PSAD < 0.15 upgraded). Conclusions: MRI PSAD is significantly associated with Gleason upgrading on follow up biopsy for men initially diagnosed with Gleason grade 3+3 disease. This finding is important because surveillance MRI is increasingly being used to monitor men on active surveillance.