MRI-Based Prostate-Specific Antigen Density Predicts Gleason Score Upgrade in an Active Surveillance Cohort

OBJECTIVE. 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 (AS) for men with disease that is at a low stage or grade. We hypothesized that elevated MRI PSAD is similarly associated with increased risk of progression on subsequent biopsy. MATERIALS AND METHODS. In this retrospective study, men with Gleason score of 3+3 on diagnostic TRUS-guided biopsy who were managed with AS, had undergone MRI, and had at least one additional biopsy were included. MRI PSAD was calculated using prostate volume on MRI and prostate-specific antigen level 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. A total of 166 patients were identified, of whom 74 (44.6%) were upgraded to a Gleason score of 7 or higher on subsequent biopsy. Lesions with Prostate Imaging Reporting and Data System (PI-RADS) scores of 4 and 5 more commonly had MRI PSAD of 0.15 ng/mL² or higher (51.93% vs 22.22%, p = 0.01) than lesions with PI-RADS scores of 1-3. Median MRI PSAD was significantly higher in the upgraded group compared with the group that was not upgraded (0.15 ng/mL² vs 0.11 ng/mL², p = 0.01). MRI PSAD was significantly associated with increased odds of upgrading on subsequent biopsy (log transformation; odds ratio, 1.9 [95% CI, 1.2-2.8]; p = 0.01) after adjusting for age and length of follow-up. CONCLUSION. MRI PSAD was significantly associated with Gleason score upgrading on subsequent biopsy for men initially diagnosed with Gleason 3+3 disease. Although this result is intuitive, to our knowledge it has not been previously shown. As MRI utilization increases, MRI PSAD can aid in risk stratification for men managed with AS.