Role of the Stockholm3 Test in Guiding Confirmation Biopsy Decisions for Patients with Prostate Cancer on Active Surveillance.

Background and objectives: The aim of our study was to assess correlation between Stockholm3 test results, multiparametric magnetic resonance imaging (mpMRI) findings, and confirmation biopsy outcomes in a cohort of patients on active surveillance (AS) for prostate cancer (PC).

Methods: The study cohort comprised 26 patients on AS for International Society of Urological Pathology grade group (GG) 1 PC. Repeat MRI and confirmation biopsy following a Stockholm3 test were performed for all. We defined a Stockholm3 score cutoff of ≥15 for higher risk of clinically significant PC (csPC). The sensitivity and negative predictive value (NPV) of the Stockholm3 test and mpMRI for prediction of csPC were assessed.

Key findings and limitations: The median age for the study cohort was 63 yr. Median PSA was 4.6 ng/ml and the median Stockholm3 score was 17. Sixteen patients (61.5%) had lesion with a Prostate Imaging-Reporting and Data System (PI-RADS) score of ≥4 on repeat mpMRI. Confirmatory biopsy revealed benign histology in five patients (19.3%), GG 1 PC in 13 patients (50%), and GG >1 PC (upgrading) in eight patients (30.7%). Using a score cutoff of ≥15 for the Stockholm3 test yielded sensitivity of 87.5% and an NPV of 90% for upgrading on confirmatory biopsy. Of 16 patients with a PI-RADS ≥4 lesion on MRI, 43.7% had csPC on confirmatory biopsy. PI-RADS ≥4 had sensitivity of 87.5% and an NPV of 90% for prediction of csPC.

Conclusions and clinical implications: For most of our 26 patients on AS with a Stockholm3 score of <15, confirmatory biopsy revealed GG 1 and benign histology. A confirmatory biopsy should be recommended for all patients with PI-RADS ≥4 lesions irrespective of their Stockholm3 score, but could be avoided in cases with negative MRI findings and a Stockholm3 score of <15.