2198. Prevalence of Prostate Cancer in PI-RADS v2.1 TZ ‘Atypical Nodules’ Upgraded by Abnormal DWI: Correlation with MRI-Directed TRUS Biopsy
Authors * Denotes Presenting Author
  1. Christopher Lim *; Department of Medical Imaging, University of Toronto; Sunnybrook Health Science Centre
  2. Jorge Abreu-Gomez; Department of Medical Imaging, University of Toronto
  3. Ivan Carrion; Department of Medical Imaging, University of Toronto; Sunnybrook Health Science Centre
  4. Nicola Schieda; Department of Radiology, University of Ottawa
The purpose of this study was to evaluate the prevalence of PCa in DWI upgraded TZ ‘atypical’ nodules and compare PCa diagnosis rate to conventional score 3 TZ nodules.

Materials and Methods:
We retrospectively identified 104 consecutive men who underwent MRI-directed TRUS-guided targeted biopsy of 109 TZ category =3 nodules performed between January 2015 and July 2018. Three blinded radiologists (R1 inexperienced, R2-3, experienced) independently re-scored lesions using PI-RADS v2.1. Agreement was assessed by Cohen’s Kappa. Consensus diagnosis was established by second-round joint review. The number of TZ ‘atypical’ nodules with or without DWI upgrade and conventional score 3 TZ nodules were recorded and compared with targeted biopsy results (any PCa or clinically significant [CS, ISUP grade group =2] PCa) using Chi-square.

There were 95 PI-RADSv2.1 category 3 (55 conventional T2W score 3 and 40 DWI upgraded ‘atypical’ nodules) and fourteen category 2 or 1 nodules at consensus review with mean age 64.8±8.4 years, PSA 10.6±7.2 ng/mL and nodule size 15.1±5.5 (range 7 to 29) mm. Inter-observer agreement ranged from slight-to-substantial, R1/2(K=0.329), R1/3(0.548) and R2/3(0.652). From the forty upgraded ‘atypical’ nodules, 27.5% (11/40) had PCa and 7.5% (3/40) had CS-PCa (ISUP 1, N=8; ISUP 2, N=2; ISUP 3, N=1), compared to 43.6% (24/55) PCa and 20.0% (11/55) CS-PCa (ISUP 1, N=13; ISUP 2, N=6; ISUP 3, N=3; ISUP 4, N=2) diagnosed in conventional T2W score 3 nodules (p=0.090, 0.101). PCa was not diagnosed in any non-DWI upgraded ‘atypical’ nodule.

This study validates the DWI upgrade rule introduced in PI-RADSv2.1 for atypical nodules, which showed similar signifi- cant prostate cancer detection rates at targeted biopsy to conventional T2-weighted TZ score 3 nodules.