ABSTRACT
OBJECTIVE: To assess the accuracy of Diffusion-Weighted MR Imaging (DW-MRI) at 3-Teslas (3T) with a b-value of 2000s/mm(2) (b-2000 DW-MRI) to detect prostate cancer (PCa) and to describe the histological features of missed tumors. METHODS: Prior to radical prostatectomy, 35 patients with a mean age of 64±6.2years old [51-77years old] had a b-2000 DW-MRI at 3-T, without rectal coil (acquisition time: 2min, 15s), and were analysed on an eight-sector basis by two independent readers blinded to the rest of the multiparametric-MRI protocol. Pathological tumor foci were matched with high intensity focal areas on MRI and correlated for Gleason score, sector location and largest axial diameter. RESULTS: Of the 280 sectors analysed, histology showed PCa in 113 (113/280, 40%). Overall DW-MRI sensitivity, specificity and accuracy for tumor detection were 79-81%, 99-95% and 92-82% for readers 1 and 2, respectively (kappa test: 0.78). Of all, 28 (28/113, 25%) and 22 (22/113, 20%) tumor foci were not detected by reader 1 and 2 respectively. These undetected tumor foci had a mean pathological axial axis of 5mm (range: 3-15mm) and a Gleason score of 6, 7 (3+4), 7 (4+3) and>7 in 15/28 (54%), 9/28 (32%), 3/28 (10%) and 1/28 (4%) of cases for reader 1, and in 11 (50%), 5 (23%), 5 (23%) and 1 (4%) of cases for reader 2. CONCLUSION: A normal b-2000 DW-MRI at 3-T may miss small tumors without or with a minor Gleason 4 component.
