Magnetic resonance imaging/transrectal ultrasonography fusion targeted prostate biopsy finds more significant prostate cancer in biopsy‐naïve Japanese men compared with the standard biopsy

Prostatic adenocarcinomas predominantly arise in the peripheral zone (PZ) of the organ; however, a significant subset of tumors (approximately 20%) originate in the transition zone (TZ). These tumors exhibit morphologic and growth pattern features suggestive of a lower degree of biologic aggressiveness. From our surgical pathology files, we identified 39 consecutive radical prostatectomy specimens in which discrete adenocarcinomas of both peripheral and transition zone origin were present. All specimens had been entirely embedded, step-sectioned, and reviewed by two urologic pathologists. DNA content was determined by image analysis of Feulgen-stained tissue sections, and cellular proliferation was evaluated by immunohistochemical staining with MIB-1. The mean Gleason score for the PZ and TZ tumors was 6.7 and 5.6, respectively (p < 0.001). Of 15 cases analyzed to date, 8 PZ tumors and 2 TZ tumors were aneuploid (p = 0.055). The proliferation indices for the PZ and TZ tumors were 5.0% and 1.6%, respectively (p < 0.05). These findings confirm other reports, supporting the concept of biological differences between carcinomas of peripheral and transitional zone origin.

Utilization of pre-biopsy multiparametric MRI (mpMRI) is increasing. To optimize the usefulness of mpMRI, physicians should accurately quote patients a numerical risk of cancer based on their MRI. The Prostate Imaging Reporting and Data System (PIRADS) standardizes interpretation of mpMRI; however, reported rates of clinically significant prostate cancer (CSC) stratified by PIRADS score vary widely. While some publications use radical prostatectomy (RP) specimens as gold standard, others use biopsy. We hypothesized that much of the variation in CSC stems from differences in cancer prevalence in RP cohorts (100% prevalence) vs biopsy cohorts. To quantify the impact of this selection bias on cancer yield according to PIRADS score, we analyzed data from 614 men with 854 lesions who underwent targeted biopsy from 2014 to 2018. Of these, 125 men underwent RP. We compared the PIRADS detection rates of CSC (Gleason ≥7) on targeted biopsy between the biopsy-only and RP cohorts. For all PIRADS scores, CSC yield was much greater in patients who underwent RP. For example, CSC was found in 30% of PIRADS 3 lesions in men who underwent RP vs 7.6% in men who underwent biopsy. Our results show that mpMRI performance appears to be better in men who undergo RP compared with those who only receive biopsy. Physicians should understand the effect of this selection bias and its magnitude when discussing mpMRI results with patients considering biopsy, and take great caution in quoting CSC yields from publications using RP as gold standard.