Differentiation of prostatitis and prostate cancer using the Prostate Imaging—Reporting and Data System (PI-RADS)

• Prostatitis can be differentiated from prostate cancer using PI-RADS, but there is significant overlap between prostatitis and other benign findings.
• Prostatitis is believed to have restricted diffusion with ADC-values ≥ 900 mm2/s.
• Borderline pathological PI-RADS scores, indistinct T2-hypointensity, and localization in the transitional zone are other characteristics that seem to make prostatitis probable.
• MRS can help to distinguish between prostatitis and other tissue.

PurposeTo determine if prostate cancer (PCa) and prostatitis can be differentiated by using PI-RADS.Materials and methods3T MR images of 68 patients with 85 cancer suspicious lesions were analyzed. The findings were correlated with histopathology. T2w imaging (T2WI), diffusion weighted imaging (DWI), dynamic contrast enhancement (DCE), and MR-Spectroscopy (MRS) were acquired. Every lesion was given a single PI-RADS score for each parameter, as well as a sum score and a PI-RADS v2 score. Furthermore, T2-morphology, ADC-value, perfusion type, citrate/choline-level, and localization were evaluated.Results44 of 85 lesions showed PCa (51.8%), 21 chronic prostatitis (24.7%), and 20 other benign tissue such as hyperplasia or fibromuscular tissue (23.5%). The single PI-RADS score for T2WI, DWI, DCE, as well as the aggregated score including and not including MRS, and the PI-RADS v2-score were all significantly higher for PCa than for prostatitis or other tissue (p < 0.001). The single PI-RADS score for MRS and the PI-RADS sum score including MRS were significantly higher for prostatitis than for other tissue (p = 0.029 and p = 0.020), whereas the other parameters were not different. Prostatitis usually presented borderline pathological PI-RADS scores, showed restricted diffusion with ADC ≥ 900 mm2/s in 100% of cases, was more often indistinctly hypointense on T2WI (66.7%), and localized in the transitional zone (57.1%). An ADC ≥ 900 mm2/s achieved the highest predictive value for prostatitis (AUC = 0.859).ConclusionProstatitis can be differentiated from PCa using PI-RADS, since all available parameters are more distinct in cases of cancer. However, there is significant overlap between prostatitis and other benign findings, thus PI-RADS is only suitable to a limited extent for the primary assessment of prostatitis. Restricted diffusion with ADC ≥ 900 mm2/s is believed to be a good indicator for prostatitis. MRS can help to distinguish between prostatitis and other tissue.