Multi-parametric (mp) MRI of prostatic ductal adenocarcinoma

Prostatic ductal adenocarcinoma (DCa) is an aggressive variant of conventional adenocarcinoma (CCa) with mixed DCa and CCa tumors comprising up to 5% of all prostate cancers. DCa may be underestimated on T2-weighted (T2W) MRI. This study assessed the mp-MRI appearance of DCa as compared with CCa.

With research ethics board approval, we identified 38 patients who underwent mp-MRI (T2W, DWI, and DCE) and radical prostatectomy (RP) between 2012 and 2014. Eight DCa in 8 patients and 39 CCa tumor foci in 30 consecutive patients were identified. Tumor volume, apparent diffusion coefficient (ADC;10(-3) mm(2) /s), and time-signal intensity (SI) curves were calculated. Parametric data were compared using the Kruskal-Wallis test and univariate regression. Time-SI curves were compared using the chi-square test.

Tumor volumes were: 1.62(±1.02) for DCa, 1.03(±0.54) for Gleason 9, 0.88(±0.93) for Gleason 7/8, and 0.26(±0.14) mL for Gleason 6. There was no difference in size between DCa and Gleason 9 (P = 0.22); however, DCa were larger than Gleason 7/8 (P = 0.03) and Gleason 6 (P = 0.003) tumors. ADC values were: 0.789(±0.22) for DCa, 1.01(±0.19) for Gleason 9, 0.992(±0.23) for Gleason 7/8 and 1.389(±0.41) 10(-3) mm(2) /s for Gleason 6 tumors. There was no difference in ADC between DCa and Gleason 9 (P = 0.14) or Gleason 7/8 (P = 0.055) tumors. There was a difference in ADC for DCa and Gleason ≥7 CCa compared to Gleason 6 tumors, (P < 0.001 and P = 0.012). All DCa demonstrated type III time-SI curves. Gleason ≥ 7 tumors demonstrated type II/III curves. Gleason 6 tumors demonstrated Type I/II time-SI curves. There was no difference in curve type between groups, (P = 0.18).

Although DCa mimics Gleason score 3 + 3 = 6 tumor at T2W MRI; DCa resembles Gleason ≥7 CCa on mp-MRI.