Courtney A. Woodfield MD, Presenter: Nothing to Disclose

David J. Grand MD, Abstract Co-Author: Nothing to Disclose

John Albert Pezzullo MD, Abstract Co-Author: Nothing to Disclose

Jason Machan, Abstract Co-Author: Nothing to Disclose

Glenn A. Tung MD, Abstract Co-Author: Nothing to Disclose

To determine if diffusion weighted imaging (DWI) improves interreader agreement for both prostate cancer identification and staging of extracapsular extension (ECE) and seminal vesicle invasion (SVI).

We performed an IRB approved retrospective review of endorectal prostate MRI performed with T2-weighted imaging and DWI on a 1.5 T magnet on men with biopsy proven prostate cancer. Single-shot echo-planar imaging DWI technique with b-values of 0 and 1000 s/mm2 was used. T2-weighted images alone (T2) or in conjunction with DWI (T2+DWI) were independently and randomly interpreted by 3 radiologists blinded to clinical data and biopsy results. On a 3 point scale (increased, no change, decreased), the readers also rated any change in confidence for tumor localization and staging with the addition of DWI. Interobserver agreement was estimated using kappa.

Prostate MRI was performed on 30 men of mean age 65.3±5.4 years with average PSA 10.5±8.0 ng/ml; 80 sextant core biopsies were positive for prostate cancer with mean Gleason Score 7±1. For tumor identification, mean kappa for T2 alone was 0.34 (range, 0.27-0.39) and for T2+DWI, k=0.59 (0.44-0.81); for staging ECE, mean kappa for T2 alone was 0.49 (0.35-0.63) and for T2+DWI, k=0.63 (0.56-0.71); for staging SVI, mean kappa for T2 alone was 0.57 (0.48-0.71) and for T2+DWI, k=0.70 (0.52-0.79). Interreader agreement increased for both tumor identification and staging of ECE and SVI in 8 of 9 comparisons, but increases in kappa were not statistically significant (p>.05). DWI increased reader confidence for tumor localization in a mean of 20 (66.7%) cases [range 15-23 (50-76.7%)], for ECE in a mean of 7 (23.3%) [1-17 (3.3-56.7%)] cases, and for SVI in a mean of 2 (6.7%) [4-20 (13.3-66.7%)] cases.

Despite the kappa increases for prostate cancer detection and staging, no statistically significant increase in reader agreement with the addition of DWI to T2 was found for this study population. Reader confidence for both tumor localization and staging did increase with the addition of DWI.

Interreader inconsistency contributes to the variable detection and staging of prostate cancer with MRI. DWI may advance interreader agreement as well as the clinical application of prostate MRI.

Woodfield, C, Grand, D, Pezzullo, J, Machan, J, Tung, G, Localization and Staging of Prostate Cancer on MR Imaging: Does Diffusion-weighted MR Imaging Increase Interreader Agreement?.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6020996.html