Pathologic and radiographic outcomes following prostate cancer diagnosis aided by IsoPSA testing.

Abstract

276 Background: IsoPSA is a structure-based assay previously demonstrated to outperform prostate specific antigen (PSA) and free-to-total PSA ratio in detecting clinically significant prostate cancer at the time of biopsy (Stovsky, Klein 2019). Herein we report pathologic outcomes in patients treated via radical prostatectomy (RP) whom had undergone IsoPSA testing prior to their diagnostic biopsy. We also explore IsoPSA status in the context of MRI dependent findings, including PIRADS scores and PSA density. Methods: We conducted a retrospective review of patients whom had undergone IsoPSA testing prior to biopsy and RP at our institution between 2019-2021. We also identified subsets of patients with pre-operative prostate MRI’s. Exploratory analyses were performed to determine associations between IsoPSA and adverse histologic (cribiform, intraductal status (CB/ID), grade group status) pathologic (extraprostatic extension, seminal vesicle involvement, surgical margins) and radiographic (PSA density, PIRADS, location) features. We examined these data points in a randomly selected control group of RP patients whom had not had IsoPSA testing. Student’s T-test, Mann Whitney U, Kruskal Wallis, were used where appropriate. Results: A total of 83 patients underwent RP following IsoPSA testing, with 72.2% (60/83) also undergoing pre-operative prostate MRI. The mean total PSA was 10.3 ng/dL, IsoPSA index was 10.2 and prostate size 46.8 cc. IsoPSA was significantly associated with PSA density (median IsoPSA of 9.9 vs 7.8 for PSA density > 0.15, <0.15 respectively, p < 0.001). The median IsoPSA index was higher when the dominant tumor was found in the transitional zone versus peripheral zone (12.7 vs 8.8 p = 0.011). IsoPSA trended towards but was not associated with PIRADS-v2 score (1-2 vs 3 vs 4-5) (p = 0.1). IsoPSA was not selectively associated with adverse pathological or histological features. Conclusions: IsoPSA has been shown to predict clinically significant disease on biopsy, and as such may improve the selection of men for such intervention. In our initial cohort, IsoPSA reliably identified patients with clinically significant disease without selecting for unique adverse pathologic/histologic features when compared to a control group. Radiographically, IsoPSA was significantly associated with elevated PSA density ( > 0.15), tumor location (TZ vs PZ), and trended towards significance with PIRADS v.2 score (p = 0.1. Further work is encouraged to explore its adjunctive benefit in correlation to MRI features.