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.