Clinically insignificant prostate cancer suitable for active surveillance according to Prostate Cancer Research International: Active surveillance criteria: Utility of PI-RADS v2

Background: Active surveillance (AS) is an important treatment strategy for prostate cancer (PCa). Prostate Imaging-Reporting and Data System (PI-RADS) v2 has been addressed, but few studies have reported the value of PI-RADS v2 for assessing risk stratification in patients with PCa, especially on selecting potential candidates for AS. Purpose: To investigate the utility of PI-RADS v2 and apparent diffusion coefficient (ADC) in evaluating patients with insignificant PCa, who are suitable for AS. Study Type: Retrospective. Subjects: In all, 238 patients with PCa who met the Prostate Cancer Research International: Active Surveillance criteria underwent radical prostatectomy. Field Strength/Sequence: 3.0T, including T ₂ -weighted, diffusion-weighted, and dynamic contrast-enhanced imaging. Assessment: Insignificant cancer was defined histopathologically as an organ-confined disease with a tumor volume <0.5 cm ³ without Gleason score 4–5. Patients were divided into two groups based on the PI-RADS v2 and tumor ADC: A, PI-RADS score ≤3 and ADC ≥1.095 × 10 ⁻³ mm ² /s; and B, PI-RADS score 4–5 or ADC <1.095 × 10 ⁻³ mm ² /s. Preoperative clinical and imaging variables were evaluated regarding the associations with insignificant cancer. Results: Of the 238 patients, 101 (42.8%) were diagnosed with insignificant cancer on pathological findings. The number of positive cores, prostate-specific antigen density (PSAD), PI-RADS v2 and tumor ADC were significantly associated with insignificant cancer on univariate analysis (P < 0.05). However, multivariate analysis indicated tumor ADC (odds ratio [OR] = 4.57, P < 0.001) and PI-RADS v2 (OR = 3.60, P < 0.001) were independent predictors of insignificant cancer. Area under the receiver operating characteristics curve (AUC) reached 0.803 when PI-RADS v2 (AUC = 0.747) was combined with tumor ADC (AUC = 0.786). Data Conclusion: The PI-RADS v2 together with tumor ADC may be a useful marker for predicting patients with insignificant PCa when considering AS. Level of Evidence: 4. Technical Efficacy: Stage 2. J. Magn. Reson. Imaging 2018;47:1072–1079.