Clinical and multiparametric MRI signatures of granulomatous prostatitis

The purpose of the study is to differentiate granulomatous prostatitis (GP) from high-grade prostate cancer (PCa) based on clinical findings and imaging characteristics on multiparametric MRI (MP-MRI).

Pathology from patients undergoing MRI/US fusion-guided prostate biopsies between 2014 and 2015 was reviewed. Five patients with biopsy proven GP were identified as well as 15 patients with biopsy-proven Gleason score ≥4 + 3 = 7 PCa. Patients were matched for age, serum PSA level, and prebiopsy-assigned MP-MRI cancer suspicion scores. MP-MRI studies were reviewed to identify findings that would differentiate GP from PCa in patients who had equally high suspicion scores based upon imaging characteristics.

All five patients with GP on MR/US fusion-targeted biopsies were assigned a PIRADS 4 or 5 suspicion score. There were equally high suspicion scores on MP-MRI for both groups (p = 0.57). Re-evaluation of the MRI characteristics of the 5 GP patients and 15 matched controls who had pathologically proven Gleason score ≥4 + 3 = 7 PCa on targeted biopsy demonstrated statistically lower mean ADC values within the index targeted lesion for PCa vs. GP (p = 0.002) Qualitatively, no patients with GP on biopsy had imaging evidence of higher-staged disease, while 33% of patients in the high-risk PCa cohort demonstrated at least one high-stage feature (p = 0.003).

Patients with GP routinely have MRIs with moderate to high levels of suspicion for harboring PCa. Re-evaluation of these patients' imaging demonstrated characteristics including significantly higher ADC values and absence of high-stage features, which may help differentiate areas of GP from PCa in the future.