The performance of PI-RADSv2 and quantitative apparent diffusion coefficient for predicting confirmatory prostate biopsy findings in patients considered for active surveillance of prostate cancer

Abstract

Purpose: To assess the performance of the updated Prostate Imaging Reporting and Data System (PI-RADSv2) and the apparent diffusion coefficient (ADC) for predicting confirmatory biopsy results in patients considered for active surveillance of prostate cancer (PCA).

Methods: IRB-approved, retrospective study of 371 consecutive men with clinically low-risk PCA (initial biopsy Gleason score ≤6, prostate-specific antigen <10 ng/ml, clinical stage ≤T2a) who underwent 3T-prostate MRI before confirmatory biopsy. Two independent radiologists recorded the PI-RADSv2 scores and measured the corresponding ADC values in each patient. A composite score was generated to assess the performance of combining PI-RADSv2 + ADC.

Results: PCA was upgraded on confirmatory biopsy in 107/371 (29%) patients. Inter-reader agreement was substantial (PI-RADSv2: k = 0.73; 95% CI [0.66-0.80]; ADC: r = 0.74; 95% CI [0.69-0.79]). Accuracies, sensitivities, specificities, positive predicted value and negative predicted value of PI-RADSv2 were 85, 89, 83, 68, 95 and 78, 82, 76, 58, 91% for ADC. PI-RADSv2 accuracy was significantly higher than that of ADC for predicting biopsy upgrade (p = 0.014). The combined PI-RADSv2 + ADC composite score did not perform better than PI-RADSv2 alone. Obviating biopsy in patients with PI-RADSv2 score ≤3 would have missed Gleason Score upgrade in 12/232 (5%) of patients.

Conclusion: PI-RADSv2 was superior to ADC measurements for predicting PCA upgrading on confirmatory biopsy.

Keywords: Biopsy; Cancer; Confirmatory; PI-RADSv2; Prostate.

Figure 1

Study design

Figure 2

Patients characteristics

Figure 3

T2 weighted image (A, D), ADC map (B, E) and fused T2 weighted image and ADC map (C, F) demonstrate a PI-RADSv2 5 lesion (white arrow) within the right transition zone (A, B, C) and left mid gland peripheral zone (D, E, F). T2 weighted image (G), ADC map (H) and fused T2 weighted image and ADC map (I) demonstrate a vague T2 (white arrow, G) non measurable lesion with mild diffusion restriction (white arrow, H, I) classified as PI-RADSv2 2 lesion. White circle on C, F and I demonstrate ADC ROI.