BACKGROUND: Prostate biopsy is not benign and should be avoided if possible. The objective of this study was to determine if initial PIRADS score could reduce the need for repeat prostate biopsy in men on active surveillance (AS) in the era of MRI-targeted fusion biopsies.
METHODS: A prospectively collected cohort of AS patients was followed with an annual MRI and surveillance MR-US fusion prostate biopsy. Clinical characteristics including age, race, DRE, maximum PIRADS, PSA, PSAD, and Gleason grade group (GGG) were used to calculate sensitivity, specificity, NPV, and PPV for initial multiparametric MRI (mpMRI) PIRADS v2 scores to predict upgrade on biopsy.
RESULTS: A total of 343 patients were enrolled in our institutional AS protocol after a preliminary prostate biopsy. Of these, 197 patients were GGG1, 105 were benign, and 41 were GGG2. The patients with benign pathology had a biopsy at another institution demonstrating prostate cancer (PCa). 343 patients underwent biopsy in year 1, and 158 patients in year 2. At year 1, 95/343 (27.6%) patients had upgraded to any PCa, defined as a higher GGG than at year 0, and 78/343 patients (22.7%) had upgraded to GGG2+ PCa, defined as a higher GGG than at year 0 which was GGG2 or higher. A PIRADS < 3 in year 0 showed that mpMRI was associated with a NPV of 83.9% for upgrade to any PCa and 95.8% for upgrade to GGG2+ on the year 1 biopsy. For PIRADS 3-5, PPV was 31.3% and 29.4%, and sensitivity was 86% and 96% for upgrade to any PCa and to GGG2+ on the year 1 biopsy, respectively. Ultimately, of the 81 patients who had an initial maximum PIRADS < 3, two had GGG2 PCa and one had GGG3 PCa at year 1 biopsy. When substratified to patients with < GGG2 disease on initial MR-fusion biopsy, a maximum PIRADS < 3 on the initial mpMRI was associated with a NPV of 86.67% for upgrade to any PCa and 86.67% for upgrade to GGG2+ PCa on the year 1 biopsy. For PIRADS 3-5, PPV was 37.69% and 35.38%, and sensitivity was 96.08% and 95.83%, for upgrade to any PCa and upgrade to GGG2+ PCa on the year 1 biopsy, respectively. In this cohort, 2 patients had GGG2+ PCa with PIRADS < 3 (both GGG2). At the year 2 biopsy, initial PIRADS < 3 was associated with a NPV of 88.9% for an upgrade to any PCa in the total cohort and a NPV of 84.62% in the < GGG2 cohort.
CONCLUSIONS: In our institutional AS protocol, foregoing a first-year fusion biopsy in patients with a maximum PIRADS < 3 is associated with reasonable diagnostic statistical support with NPV >90% and sensitivity >90%. To be adequately assessed, the timing of prostate biopsies in AS protocols should be verified by institutional data prior to implementation.
