Introduction: Multiparametric magnetic resonance imaging (MRI) improved the detection rate of clinically significant prostate cancer (csPCa). However, a significant proportion of patients with highly-suspicious MRI findings are found to have no cancer on histological examination after biopsy. We investigated whether high-resolution micro-ultrasound (mUS) might be able to stratify this population according to the risk of harboring csPCa.
Methods: We analyzed 126 consecutive patients scheduled for a prostate biopsy with =1 PIRADS 5 lesion at MRI. Before biopsy, all patients underwent a mUS examination by an operator blinded to MRI result. The Prostate Risk Identification using MicroUS (PRIMUS) protocol was used to assess the risk of csPCa, defined as ISUP >1 PCa. All patients received both targeted and systematic biopsies. The primary endpoint was to determine the diagnostic accuracy of mUS. Multivariable logistic regression models (MLRM) were fitted to identify predictors of csPCa. The diagnostic accuracy was reported as area under the ROC curve. Finally, we evaluated the diagnostic value of mUS in non-biopsy-naïve patients with PIRADS 5 lesions at MRI.
Results: Overall, 76 (60.3%) patients were biopsy-naïve, while 50 (39.7%) had =1 previous biopsy. Median age was 69years (IQR 61-74), median PSA was 9.1ng/ml (IQR 6.6-13). Overall, 93 (73.81%) patients were diagnosed with PCa and 81 (64.3%) had csPCa. MUS detected a suspicious (i.e. PRIMUS >2) lesion in 102 (81.0%) patients; of those, 75 (73.5%) were diagnosed with csPCa. MUS sensitivity was 73.5%, specificity 75.0%, positive predictive value 92.6%, and negative predictive value (NPV) 40.0%. At MLRM, factors associated with csPCa were: a positive mUS assessment (OR: 8.44, 95%CI: 2.17-32.92), increasing age (OR: 1.09, 95%CI: 1.02-1.16), being biopsy-naïve (OR: 8.63, 95%CI: 2.95-25.23), and a PSA density >15% (OR: 3.16, 95%CI 1.13-8.83). The accuracy of a model including those 4 variables was 0.83 (95%CI: 0.74-0.92). Of 50 patients with a PRIMUS 5 lesions who already had =1 previous biopsy, 12 (24%) and 38 (76%) had a negative and positive mUS assessment, respectively. Among mUS-negative patients, only 1 (4.6%) was diagnosed with csPCa at pathological examination. In this subgroup, mUS had a NPV of 91.7%.
Conclusions: MUS is a highly accurate diagnostic tool in patients presenting with a PIRADS 5 lesion at MRI. Together with easily available clinical variables, it might be able to further stratify csPCa risk in this population. Whether this information can improve the follow-up of these patients needs to be answered yet.
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