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. 2013 Dec;82(12):e775-81.
doi: 10.1016/j.ejrad.2013.09.011. Epub 2013 Sep 22.

MRI findings of radiation-induced changes in the urethra and periurethral tissues after treatment for prostate cancer

Chiara Marigliano  1 , Olivio F Donati, Hebert Alberto Vargas, Oguz Akin, Debra A Goldman, James A Eastham, Michael J Zelefsky, Hedvig Hricak
Affiliations

MRI findings of radiation-induced changes in the urethra and periurethral tissues after treatment for prostate cancer

Chiara Marigliano et al. Eur J Radiol. 2013 Dec.

Abstract

Purpose: To assess radiotherapy (RT)-induced changes in the urethra and periurethral tissues after treatment for prostate cancer (PCa).

Methods and materials: This retrospective study included 108 men (median age, 64 years; range, 43-87 years) who received external-beam radiotherapy (EBRT) and/or brachytherapy for PCa and underwent endorectal-coil MRI of the prostate within 180 days before RT and a median of 20 months (range, 2-62 months) after RT. On all MRIs, two readers independently measured the urethral length (UL) and graded the margin definition (MD) of the urethral wall and the signal intensities (SIs) of the urethral wall and pelvic muscles on 4-point scales.

Results: The mean urethral length decreased significantly from pre- to post-RT MRI (from 15.2 to 12.6mm and from 14.4 to 12.9 mm for readers 1 and 2, respectively; both p-values <0.0001). Brachytherapy resulted 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 SI increase in pelvic muscles depended on muscle location. In the obturator internus muscle, SI increased more often after EBRT than after brachytherapy, while in the periurethral levator ani muscle SI increased more often after brachytherapy than after EBRT.

Conclusion: After RT for PCa, MRI shows urethral shortening and increased SI of the urethral wall and pelvic muscles in substantial percentages of patients.

Keywords: MRI; Prostate cancer, Urethra; Radiation therapy.

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Conflict of interest statement

Conflict of interest: none

Figures

Figure 1
Figure 1
Coronal T2-weighted images from a 68-year old patient who underwent EBRT (8640 cGy) for prostate cancer. Measurements taken by readers 1 and 2 indicated that the urethral length measured from prostatic apex to penile bulb (red lines) decreased by 7 mm and 8 mm, respectively, between pre-RT MRI (A) and post-RT MRI (B). Axial T2-weighted images pre-RT (C) and post-RT (D) of a 54-year old man who underwent brachytherapy (144Gy) demonstrates an increase in SI of the urethral wall from “isointense” (C) to “hyperintense” (D).
Figure 2
Figure 2
Left-hand column: T2-weighted images from a 70-year-old patient who underwent EBRT (8640 cGy). The images demonstrate an increase in SI between pre- and post-RT MRI in the obturator internus muscle (arrowheads). Right-hand column: T2-weighted images from a 59-year old patient who underwent brachytherapy (144 Gy) for prostate cancer. The images demonstrate an increase of SI (asterisks) between pre- and post-RT MRI in the periurethral part of the levator ani muscle (LA periurethral).
Figure 3
Figure 3
Axial and coronal T2-weighted images from a 73-year old patient who underwent brachytherapy (144 Gy) for prostate cancer. The urethral wall is sharply demarcated on pre-RT MRI (arrowheads). On post-RT MRI, the margin of the urethral wall (arrowheads) is less sharply demarcated.
See this image and copyright information in PMC

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