Abstract: |
Purpose: To assess radiotherapy (RT)-induced changes in the urethra and periurethral tissues after treat-ment for prostate cancer (PCa).Methods and materials: This retrospective study included 108 men (median age, 64 years; range, 43?87years) who received external-beam radiotherapy (EBRT) and/or brachytherapy for PCa and underwentendorectal-coil MRI of the prostate within 180 days before RT and a median of 20 months (range, 2?62months) after RT. On all MRIs, two readers independently measured the urethral length (UL) and gradedthe margin definition (MD) of the urethral wall and the signal intensities (SIs) of the urethral wall andpelvic muscles on 4-point scales.Results: The mean urethral length decreased significantly from pre- to post-RT MRI (from 15.2 to 12.6 mmand from 14.4 to 12.9 mm for readers 1 and 2, respectively; both p-values 〈0.0001). Brachytherapyresulted in greater urethral shortening than EBRT. After RT, SI in the urethral wall increased in 57%(62/108) and 35% (38/108) of patients (readers 1 and 2, respectively). The frequency and magnitude of SIincrease in pelvic muscles depended on muscle location. In the obturator internus muscle, SI increasedmore often after EBRT than after brachytherapy, while in the periurethral levator ani muscle SI increasedmore often after brachytherapy than after EBRT.Conclusion: After RT for PCa, MRI shows urethral shortening and increased SI of the urethral wall andpelvic muscles in substantial percentages of patients. © 2013 Elsevier Ireland Ltd. All rights reserved. |