Using IsoPSA with PI-RADS Score May Help Refine Biopsy Decision Making in Patients with Elevated PSA.

OBJECTIVE: To assess how IsoPSA, a structure-based serum assay which has been prospectively validated in detecting clinically significant prostate cancer (csPCa), can help the biopsy decision process when combined with the Prostate Imaging Reporting and Data Systems (PI-RADS).

MATERIALS AND METHODS: This was a single-center retrospective review of prospectively collected data on patients receiving IsoPSA testing for elevated PSA (>4.0ng/mL). Patients were included if they had received an IsoPSA test and prostate MRI within one year of IsoPSA testing, and subsequently underwent prostate biopsy. Multivariable logistic regression was used to identify predictors of (csPCa i.e. GG ≥ 2) on biopsy. Predictive probabilities for csPCa at biopsy were generated using IsoPSA and various PI-RADS scores.

RESULTS: Two hundred and seven patients were included. Twenty-two percent had csPCa. Elevated IsoPSA ratio (defined as ≥6.0) (OR: 5.06, p=0.015) and a PI-RADS 4-5 (OR: 6.37, p<0.001) were significant predictors of csPCa. The combination of elevated IsoPSA ratio and PI-RADS 4-5 lesion had the highest area under the curve (AUC) (AUC: 0.83, p<0.001). The predicted probability of csPCa when a patient had a negative or equivocal MRI (PI-RADS 1-3) and a low IsoPSA ratio (≤6) was <5%.

CONCLUSION: The combination of PI-RADS with IsoPSA ratios may help refine the biopsy decision-making process. In our cohort, a negative or equivocal MRI with a low IsoPSA may provide a low enough predicted probability to omit biopsy in such patients.