S-PI-RADS and PI-RRADS for Biparametric MRI in the Detection of Prostate Cancer and Post-treatment Local Recurrence

Abstract The application of biparametric magnetic resonance imaging (bpMRI) [T2-weighted (T2W) and diffusion weighted imaging (DWI)/apparent diffusion coefficient (ADC)] using dedicated structured methods, such as Simplified Prostate Imaging Reporting and Data System (S-PI-RADS) for the detection, categorization, and management of prostate cancer (PCa) is reported. Also, Prostate Imaging Reporting for Local Recurrence and Data System (PI-RRADS) for the detection and assessment of the probability of local recurrence after radiotherapy (RT) or radical prostatectomy (RP) in patients with biochemical recurrence (BCR) is proposed. Both S-PI-RADS and PI-RRADS assign to DWI/ADC a main role for the above purpose. S-PI-RADS identifies four categories and, on the basis of the qualitative and quantitative analysis of the restricted diffusion on ADC map and lesion volume, distinguishes two categories of lesions: category 3 (moderately homogeneous hypointense on ADC map) and category 4 (markedly homogeneous or inhomogeneous hypointense on ADC map). Ιn category 3, two subcategories (3a: volume <0.5 cm3 and 3b: volume ≥0.5 cm3) suggesting clinical management. PI-RRADS distinguishes four assessment categories and suggests the stratification of the probability (ranging from very low for category 1 to very high for category 4) of local disease recurrence. In clinical practice, S-PI-RADS and PI-RRADS, based on bpMRI represent a potential valid approach that may facilitates the detection and management of PCa and for detecting local recurrence after treatment improving communication with other professionals.