A scoring system radiologists use to determine the risk of clinically significant prostate cancer (PCa) on multiparametric magnetic resonance imaging (mpMRI) scans often produces false positives, with chronic inflammation and benign histology among the reasons, according to study findings presented at the Society of Urologic Oncology 2020 virtual annual meeting.

Patients who have PI-RADS (Prostate Imaging Reporting and Data System) 5 lesions on mpMRI have the highest risk for clinically significant cancer, but a significant proportion of PI-RADS 5 lesions do not demonstrate clinically significant cancer on MRI-ultrasound fusion biopsy (FBx), investigators Farzaan Kassam, a medical student at the University of Cincinnati in Cincinnati, Ohio, and colleagues explained.

Kassam’s team examined the common reasons behind the findings of benign or non-clinically significant PCa on FBx of PI-RADS 5 lesions. Of 631 patients who underwent FBx from January 2014 to March 2020, 183 had the biopsy because of the presence of one or more PI-RADS 5 lesions. Biopsy findings revealed that 142 patients (77.6%) had clinically significant cancer, defined as a Gleason score 7 or higher cancer. Of the remaining 41 patients, 34 (82.9%) had true PI-RADS 5 lesions. In this group, 26 (76.5%) had no finding of clinically significant cancer on standard template biopsy. The causes for the false positives included true Gleason 6 cancer (46.2%), chronic inflammation (23.1%), benign histology (23.1%), acute inflammation/prostatitis (15.4%), and atrophy (15.4%) in the prostate, according to the investigators.

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Kassam F, Levin B, Tobler J, et al. The efficacy of PI-RADS scoring in predicting presence of clinically significant prostate cancer on MRI-fusion biopsy. Presented at: Society of Urologic Oncology 2020 virtual annual meeting, December 3-5. Poster 162.