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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
Objective:
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.

Results:
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.

Conclusion:
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.