Prostate-specific Antigen Density as a Proxy for Predicting Prostate Cancer Severity: Is There Any Difference between Systematic and Targeted Biopsy?

Abstract

Background: Prostate cancer screening with prostate-specific antigen (PSA) can result in unnecessary biopsies and overdiagnosis. Alternately, PSA density (PSAD) calculation may help support biopsy decisions; however, evidence of its usefulness is not concrete.

Objective: To evaluate the predictive value of PSAD for clinically significant prostate cancer detection by systematic and MRI-targeted biopsies.

Methods: This prospective study was conducted at two tertiary hospitals in Riyadh, Saudi Arabia, between December 2018 and November 2021. Patients suspected of prostate cancer were subjected to multi-parametric MRI, and for those with positive findings, systematic and targeted biopsies were performed. Clinically non-significant and significant prostate cancer cases were classified based on histopathology-defined ISUP grade or Gleason score. The PSAD was measured using the prostate volume determined by the MRI and categorized into ≤0.15, 0.16-0.20, and >0.20 ng/ml² subgroups.

Results: Systematic and targeted biopsies were carried out for 284 patients. The discriminant ability of PSAD is higher in MRI-targeted biopsy compared with systematic biopsy (AUC: 0.77 vs. 0.73). The highest sensitivity (97%) and specificity (87%) were detected at 0.07 ng/ml² in targeted biopsy. More than half of the clinically significant cases were detected in the >0.2 ng/ml² PSAD category (systematic: 52.4%; targeted: 51.1%). The CHAID methodology found that the probability of having clinically significant cancer (CSC) in patients with PSAD >0.15 ng/ml² was more than threefold than that in patients with PSAD ≤0.15 ng/ml² (64% vs. 20.2%). When considered by age, in PSAD ≤0.15 ng/ml² subgroup, the percentage of CSC detection rate increased from 20.2% to 24.6% in patients aged ≥60 years.

Conclusion: PSAD has good discriminant power for predicting clinically significant prostate cancer. A cutoff of 0.07 ng/ml² should be adopted, but should be interpreted with caution and by considering other parameters such as age.