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

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.

Prostate Imaging for Local Recurrence Reporting and Data System for Biparametric Magnetic Resonance Imaging: A Proposal.

We investigated a novel dedicated Prostate Imaging for Local Recurrence Reporting and Data System (PI-RRADS) in biochemical recurrence after radiotherapy (RT) and rad- ical prostatectomy (RP) evaluating biparametric magnetic resonance imaging (bpMRI) exams, at 3T MRI of 55 patients. Associating bpMRI and biochemical recurrence data, we calculated bpMRI diagnostic accuracy. Four probability categories, from 1 (very low) to 4 (very high), were distinguished. In 20 patients with radiotherapy, 25% and 75% of lesions were reported as PI-RRADS 3, and 4, respectively. In 35 patients with radi- cal prostatectomy, 7.7% of lesions were included in PI-RRADS 1-2, whereas 40.4% and 51.9% in PI-RRADS 3 and 4 categories, respectively. Excellent agreement and significant correlation between bpMRI and biochemical recurrence were found. BpMRI showed sensitivity, specificity, positive predictive value, negative predictive value, false-posi- tive value, false-negative value, and total diagnostic accuracy of 96.15%, 86.7%, 97.4 %, 81.25%, 13.3%, 3.8% and 94.6%, respectively. BpMRI-based PI-RRADS allows the detection and localization local recurrence in biochemical recurrence after RT and RP contributing in clinical management and treatment.

MRI apparent diffusion coefficient (ADC): A biomarker for prostate cancer after radiation therapy.

Prostate specific antigen (PSA) remains the most used test to assess the response after therapies including the radiation therapy (RT). Apparent diffusion coefficient (ADC) derived from the conventional diffusionweighted imaging (DWI), as a part of noncontrast or biparametric MRI (bpMRI) (T2-weighted and DWI), offers diagnostic accuracy and cancer detection rate equivalent to that of multiparametric MRI. Cellular changes induced by RT can be quali-qualitatively demonstrated as early as 3months after RT as an increase in the signal intensity of the tumor on the ADC map. ADC, in association with PSA, represents a potential biomarker imaging for evaluating treatment efficacy in PCa both during and shortly after RT.