Locoregional staging of prostatic carcinoma: accuracy of magnetic resonance with endorectal coil in 75 patients treated with radical prostatectomy

Introduction: We investigated the accuracy of MRI of the prostate with an endorectal surface coil in determing penetration of the prostatic capsule and invasion of seminal vescicles in prostate carcinoma. Material and methods: Endorectal coil MRI (1 Tesla) was performed in 300 patients with biopsy-proved cancer. The PSA levels were always calculated and all the patients were examined with transrectal ultrasound. The imaging protocol included Turbo Spin Echo T2-weigthed (3900/150 TR/TE) axial and coronal images and T1-weigthed (650/15 TR/TE) axial images, 4 mm thick interleaved sections with .4 mm intersection gap, FOV 180 mm, 256 x 256 matrix (reconstruction 512). Seventy-five patients underwent radical prostatectomy and MR images were compared with pathologic findings of capsular penetration and invasion of seminal vescicles. The MR signs specific for capsular penetration were: deformation (irregularity) of capsular profile, capsular retraction with irregular margins, capsular interruption, obliteration of periprostatic adipose tissue, asymmetry of neurovascular bundles. Results: MRI correctly depicted 37 of 45 pathologic stage T2 lesions and correctly depicted macroscopic capsular penetration (T3) in 18 of 23 cases. Microscopic capsular penetration was overestimated in all 7 cases. Sensitivity, specificity, accuracy, for microscopic and macroscopic capsular penetration were 60, 82, 73% respectively. Sensitivity, specificity, accuracy for macroscopic capsular penetration were 78, 82, 80% respectively. Sensitivity, specificity, accuracy for depiction of seminal vesicle involvment were 80, 100, 93%, respectively. The most reliable signs of capsular penetration were capsular interruption and invasion of periprostatic adipose tissue, while asymmetry of the neurovascular bundle was not seen. Conclusions: MRI provides accurate preoperative local staging. The two main limitations of MRI were the high rate of microscopic capsular penetration and the difficulty in detecting capsular penetration of tumor when the lesions are in the prostate apex. Prostate enlargement also made diagnosis more difficult.