経直腸的MRIの限局性前立腺癌に対する有用性についての検討

Abstract

1)前立腺癌部位はT2強調像で, 大部分が低信号で, 一部が中間信号で認められた.前立腺被膜浸潤は, 被膜断裂像・辺縁不規則像・前立腺周囲の静脈叢の低信号・前立腺周囲脂肪織の低信号で表された.精嚢腺浸潤は, 造影T1強調像の高信号とT2強調像の低信号で表された.又, T2強調像で前立腺の鮮明なzonal anatomyがみられた. 2)Stagingの正診率は, TRUSでは57%, 経直腸的MRIでは79%であった.精嚢腺浸潤の正診率は, TRUSで57%, 経直腸的MRIでは93%と, 統計学的に有意差を認めた. 3)Neoadjuvant治療の前後で, 前立腺全体の縮小率は43.2%であった

We retrospectively studied the staging accuracy of endorectal magnetic resonance imaging (MRI) using a surface coil for 14 localized prostatic cancers resected by retropubic radical prostatectomy. The prostatic tumor in the peripheral zone was mostly demonstrated as a low signal intensity on the T2 weighted image, and prostatic capsular invasion was indicated as an interruption of prostatic capsule, irregularity of glandular margins, and a low signal intensity of periprostatic venous plexus on the T2 weighted image. The seminal vesicular invasion was seen as a high signal intensity on the enhanced T1 weighted image, and a low signal intensity on the T2 weighted image. The clear prostatic zonal anatomy was demonstrated on the T2 weighted image. The accuracies of clinical staging in endorectal MRI and transrectal ultrasound examination (TRUS) were 79% and 57%, respectively. Also, the accuracies of seminal vesicular invasion in endorectal MRI and TRUS were 93% and 57%, respectively. The endorectal MRI revealed more accurately the seminal vesicular invasion than TRUS (p = 0.038), but there was no significant difference in the accuracy of detecting prostatic capsular invasion between endorectal MRI (79%) and TRUS (71%). The reduction of prostatic volume after 4 months of endocrine neoadjuvant therapy (LH-RH agonist) was compared in each prostatic intraglandular zone with the T2 weighted image. The total prostatic reduction rate was 43.2%. The reduction rate in the peripheral zone (64.8%) was more than two-fold that (29.7%) in the central gland (transition zone + central zone). The endorectal MRI may greatly contribute to the local staging of prostatic cancer, especially to the diagnosis of seminal vesicular invasion.