[MRI of the prostate after combined radiotherapy (afterloading and percutaneous): histopathologic correlation].
OBJECTIVE
To identify the MRI changes of the prostate after combined (high-dose rate interstitial with external beam) radiotherapy for, localized prostate cancer and to correlate the findings with histology in order to determine the value of MR imaging in the follow-up of these patients.


METHODS
Twenty-three patients underwent MR imaging at 1.5 T between 6 and 24 months after completion of combined radiotherapy. The prostate was imaged with axial and coronal T2-weighted sequences and axial T1-weighted sequences before and after intravenous administration of Gd-DTPA. Quadrant or sextant biopsy was performed in all cases and three patients with proven persistence of the tumor underwent salvage prostatectomy. The MRI findings were compared with the biopsy results or the large-area sections.


RESULTS
On T2-weighted images the fibrotically changed peripheral zone was hypointense while persistent tumor tissue showed hyperintensity. Solid tumors were depicted when they had a diameter of 1 cm or more. Persistent tumors of the diffuse multifocal type escaped detection. Contrast-enhanced T1-weighted imaging yielded no additional information. The accuracy in detecting persistent tumor was 74%.


CONCLUSIONS
Histopathologic changes seen after combined radiotherapy correlate with the findings on T2-weighted MR images. MR imaging cannot replace follow-up by routine biopsy. Its only role is assessing local operability in cases found to have increasing PSA levels during follow-up. Further studies are needed to determine the role of MR imaging in this patient population.
Beyersdorff
D
D
Institut für Radiologie, Charité, Humboldt-Universität zu Berlin. dirk.beyersdorff@charite.de
Taupitz
M
M
Deger
S
S
Rudolph
B
B
Dinges
S
S
Schnorr
D
D
Loening
S
S
Hamm
B
B
D000328:Adult; D000368:Aged; D001918:Brachytherapy; D003287:Contrast Media; D005355:Fibrosis; D019786:Gadolinium DTPA; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011467:Prostate / Q000473:pathology* / Q000528:radiation effects; D011471:Prostatic Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D011878:Radiotherapy / Q000379:methods
D003287:Contrast Media; D019786:Gadolinium DTPA