Abstract
Purpose: To compare diagnostic performance of PI-RADSv2 with ADC parameters to identify clinically significant prostate cancer (csPC) and to determine the impact of csPC definitions on diagnostic performance of ADC and PI-RADSv2.
Methods: We retrospectively identified treatment-naive pathology-proven peripheral zone PC patients who underwent 3T prostate MRI, using high b-value diffusion-weighted imaging from 2011 to 2015. Using 3D slicer, areas of suspected tumor (T) and normal tissue (N) on ADC (b = 0, 1400) were outlined volumetrically. Mean ADC(T), mean ADC(N), ADC(ratio) (ADC(T)/ADC(N)) were calculated. PI-RADSv2 was assigned. Three csPC definitions were used: (A) Gleason score (GS) >= 4 + 3; (B) GS >= 3 + 4; (C) MRI-based tumor volume > 0.5 cc. Performances of ADC parameters and PI-RADSv2 in identifying csPC were measured using nonparametric comparison of receiver operating characteristic curves using the area under the curve (AUC).
Results: Eighty five cases met eligibility requirements. Diagnostic performances (AUC) in identifying csPC using three definitions were: (A) ADC(T) (0.83) was higher than PI-RADSv2 (0.65, p = 0.006); (B) ADC(T) (0.86) was higher than ADC(ratio) (0.68, p < 0.001), and PI-RADSv2 (0.70, p = 0.04); (C) PI-RADSv2 (0.73) performed better than ADC(ratio) (0.56, p = 0.02). ADC(T) performance was higher when csPC was defined by A or B versus C (p = 0.038 and p = 0.01, respectively). ADC(ratio) performed better when csPC was defined by A versus C (p = 0.01). PI-RADSv2 performance was not affected by csPC definition.
Conclusions: When csPC was defined by GS, ADC parameters provided better csPC discrimination than PI-RADSv2, with ADCT providing best result. When csPC was defined by MRI-calculated volume, PI-RADSv2 provided better discrimination than ADC(ratio). csPC definition did not affect PI-RADSv2 diagnostic performance.
