• Stephen Currin, Trevor A Flood, Satheesh Krishna, Afshin Ansari, McInnes Matthew D F MDF Department of Medical Imaging, Ottawa Hospital, Ottawa, Ontario, Canada., and Nicola Schieda.
• Department of Medical Imaging, Ottawa Hospital, Ottawa, Ontario, Canada.
• J Magn Reson Imaging. 2019 Jul 1; 50 (1): 279-287.

BackgroundProstatic intraductal carcinoma (IDC-P) is an aggressive variant of prostate cancer (PCa) characterized by proliferation of malignant cells within prostatic ducts/acini and nucleomegaly.Purpose/HypothesisTo compare apparent diffusion coefficient (ADC) values and Prostate Imaging and Data Reporting System (PI-RADS) v. 2 scores in intermediate risk (International Society of Urological Pathology [ISUP] Grade Group [GG] 2 and 3) PCa with/without IDC-P to determine if IDC-P alters the MRI appearance of PCa.Study TypeRetrospective, case-control.PopulationFifteen consecutive men with ISUP GG 2/3 (Gleason score 3+4 = 7 [N = 4], 4+3 = 7 [N = 11]) PCa with IDC-P diagnosed at radical prostatectomy were compared with: 1) ISUP GG 2/3 PCa without IDC-P (matched for percentage Gleason pattern 4), and 2) ISUP GG 4 and 5 (Gleason score 8/9) PCa without IDC-P.Field Strength/Sequence3T multiparametric MRI.AssessmentTwo blinded radiologists (R1/R2) measured mean ADC, ADC.ratio (ADC.tumor/ADC.normal peripheral zone) and assigned PI-RADS v2 scores. Statistical Tests: Chi-square and analysis of variance (ANOVA).ResultsThere were no differences in age, prostate serum antigen, tumor size, or stage between groups (P = 0.063-0.912). Tumors with IDC-P had lower mean ADC and ADC.ratio (0.741 ± 0.152 mm2 /sec and 0.44 ± 0.07) compared with ISUP GG 2/3 tumors without IDC-P (0.888 ± 0.167 mm2 /sec and 0.62 ± 0.14), P = 0.012 and <0.001; and did not differ compared with ISUP GG 4/5 tumors (0.705 ± 0.141 mm2 /sec and 0.44 ± 0.08), P = 0.509 and 0.868. Tumors with IDC-P were nearly all PI-RADS v2 score 5 (14/15) compared with ISUP GG 2/3 tumors without IDC-P (10/15 R1, 8/15 R2) and GG 4/5 tumors (9/15), (P = 0.040 = 0.092). Agreement in PI-RADS v2 scoring was moderate (K = 0.68).Data ConclusionISUP GG 2 and 3 (intermediate risk, Gleason score 7) PCa with IDC-P have lower ADC compared with tumors without IDC-P with a similar percentage of Gleason pattern 4 and resemble ISUP GG 4 and 5 high risk tumors on MRI. IDC-P lowers ADC values among intermediate risk prostate cancers.Level Of Evidence3 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2019;50:279-287.© 2018 International Society for Magnetic Resonance in Medicine.

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