Medical Student Cleveland Clinic Lerner College of Medicine
Introduction: IsoPSA is a structure-based assay that has been prospectively validated to outperform total PSA and percentage free PSA in detecting clinically significant prostate cancer (csCaP) defined as Grade Group (GG) > 2. If IsoPSA is to be utilized as a biopsy triage method, it should not miss cancers with unfavorable histologic features such as cribriform (CF) or intraductal carcinoma (IDC). Therefore, we sought to investigate the ability of IsoPSA to identify patients with these unfavorable morphologic features. Methods: This was a retrospective review of patients who underwent PSA, IsoPSA, and prostate biopsy from 2017-2022. All biopsies were read by dedicated genitourinary pathologists and included CF/IDC status. Our primary outcome was the sensitivity of an elevated IsoPSA ratio (defined as IsoPSA >6) in detecting either CF or IDC at biopsy. We also compared the discriminatory power of total PSA to IsoPSA by receiving operating characteristic curves. Results: Nine-hundred and sixty one men underwent biopsy, 54.4% (523/961) were diagnosed with CaP among which 60% had csCaP. In our CaP cohort, 32.7% (174/523) had positive CF/IDC at biopsy. IsoPSA > 6 had a 94.2% sensitivity and 16.6% specificity for identifying men with these unfavorable morphologic features. The PPV was 20% and the NPV was 94%. Patients with CF/IDC had higher median IsoPSA than those that did not (10.3 vs. 8.2, p<0.001). The area under the curve for IsoPSA was 0.67 compared to 0.62 for total PSA (Figure 1, p<0.001). Conclusions: IsoPSA is highly sensitive for not only csCaP but also unfavorable histologic features including CF/IDC status. This association may not only help inform the need for biopsy but also refine treatment selection when considering active surveillance, focal therapy or whole gland treatments. SOURCE OF Funding: N/A
