Staff Urologist Santa Maria della Misericordia University Hospital
Introduction: With the advent of the novel MRI-based pathway for prostate cancer (PCa) detection, there is intense research to implement risk-adjusted strategies for the proper selection of biopsy patients and the reduction of false-negative results. In this study we investigated the clinical utility of different thresholds of PSA density (PSAD) in improving the accuracy of Prostate Imaging – Reporting And Data System version 2.1 (PI-RADS v2.1) categories for detecting clinically significant PCa on multiparametric MRI (mpMRI) and mpMRI-targeted and systematic biopsy.
Methods: A total of 123 consecutive biopsy-naïve men referred to mpMRI and prostate biopsy between April 2019 and October 2020 were retrospectively analysed. mpMRI was performed on a 3.0T magnet with a 32-channel surface coil, using a PI-RADS v2.1-compliant protocol. Two readers (>1500 and >500 mpMRI examinations) were included. All patients underwent transperineal mpMRI-targeted and systematic prostate biopsy. Clinically significant PCa was defined as International Society of Urogenital Pathology grading group =2 on combined biopsy. Analysis was performed on a per-index lesion basis. Receiver operating characteristic analysis was used to calculate sensitivity, specificity, and area under the curve (AUC) of PI-RADS v2.1 categories after adjusting for different PSAD thresholds (=0.10, =0.15, and =0.20 ng/mL/mL). Cancer detection rate (CDR) was calculated on a per-adjusted category basis, and decision analysis was performed to assess the net benefit of different PSAD-adjusted PI-RADS v2.1 categories as a biopsy trigger.
Results: Clinically significant PCa was found in 54/123 men (43.9%; 95%CI 40.5-70.4). PSAD-adjustment increased the CDR of PI-RADS v2.1 category 4 regardless of the threshold. Sensitivity/specificity/AUC were 92.6%/53.6%/0.82 for unadjusted PI-RADS, and 85.2%/72.4%/0.84, 62.9%/85.5%/0.83, and 92.4%/53.6%/0.82 when adjusting PIRADS categories for a 0.10, 0.15, and 0.20 ng/ml/ml PSAD threshold, respectively. The greatest net benefit at 30% and 40% risk probability of clinically significant PCa (0.307 and 0.271, respectively) was observed assuming biopsy patients with a PI-RADS 4 observation and PSAD =0.10 ng/mL/mL.
Conclusions: Within the range of expected prevalence for clinically significant PCa, decision analysis showed that PI-RADS v2.1 category 4 with high PSAD at the 0.10 ng/mL/mL threshold was the biopsy-triggering cut-off with the highest net benefit. If confirmed in larger prospective studies, our results might emphasize the concept that the combination of lower PSAD threshold and higher PI-RADS v2.1 cut-off may allow for better risk stratification of men referred to prostate biopsy.
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.jpg "Gianluca Giannarini, MD photo")