Multiparametric magnetic resonance imaging (mpMRI) and PSA density for the prediction of reclassification among patients under active surveillance.

Abstract

e16606 Background: To study the role of mpMRI and PSA density in predicting the likelihood of disease reclassification on re-biopsy and on final pathology among men with low-risk prostate cancer (PCa) enrolled in active surveillance (AS) protocol. Methods: In this IRB-approved prospective study, consecutive patients on AS for low-risk PCa (clinical stage cT1–T2a, Gleason score ≤6, serum PSA < 10 ng/mL, no more than 3 positive cores on biopsy, and all biopsy cores with < 50% of tumor involvement) from March 2015 to August 2017 were selected. The exclusion criteria were previous PCa treatment, contraindication to mpMRI or transrectal ultrasound-guided (TRUS) biopsy. All patients underwent mpMRI ≥3 months from initial biopsy and MRI-targeted TRUS-guided re-biopsy within 6-12 months. One experienced radiologist evaluated all mpMRI studies using the PI-RADS v2. The performance of mpMRI and PSA density for the prediction of reclassification on re-biopsy and final pathology was assessed. A single genitourinary pathologist reviewed all the final specimens who was blinded to the initial biopsy results. Results: A total of 154 patients were included in the final analysis. Among patients classified as PI-RADS ≤3, 11/69 (15.9%) were upgraded on re-biopsy whereas 65/85 (76.5%) were upgraded among those with PI-RADS 4 or 5 lesions. With regards to prostatectomy 7/49 (14.2%) patients classified as PI-RADS ≤3 were upgraded, while 42/49 (85.7%) were upgraded among those with PI-RADS 4 or 5. mpMRI sensitivity was 85.5% and specificity 74.4% on re-biopsy and 85.7% and in predicting upgrade on reclassification. Patients with PI-RADS 4 or 5 and PSA density > 0.15 ng/mL/cm3 had 94.6% of chance of having clinically significant PCa, while patients with PI-RADS 1, 2 or 3 and PSA density ≤ 0.08 ng/mL/cm3 had only 4.2% probability. Conclusions: mpMRI and PSA density are significant tools for predicting severity reclassification on re-biopsy and final pathology among patients under active surveillance. Reclassification was low among patients with PI-RADS ≤3 and low PSA density. Overall, patients with PI-RADS 4 or 5 and PSA density > 0.15 were almost invariably found to harbor significant prostate cancer.