Transurethral microwave thermotherapy of the prostate--evaluation with MRI and analysis of parameters relevant to outcome.
OBJECTIVE
To evaluate morphological changes in the hyperplastic prostate tissue following transurethral microwave thermotherapy and to investigate the dependence of the treatment outcome on structural and physiological features of the prostate.


METHODS
In this prospective study, 13 patients with chronic urinary retention due to benign prostatic hyperplasia (BPH) underwent Coretherm (ProstaLund, Lund, Sweden) microwave thermotherapy. Prior to the treatment and 1 week and 6 months after, the patients were examined with MRI using morphologic, contrast medium-enhanced perfusion and diffusion-weighted imaging. Such advanced MRI techniques permit an assessment of parameters that have a hypothetical influence on microwave thermotherapy (e.g. prostate blood perfusion, water content and prostate microstructure).


RESULTS
Morphologic and perfusion MRI showed a clear prostatic tissue defect in all 13 patients after 1 week and in all 12 patients at 6 months' follow-up. The mean size of the defect was 22.5 cm(3) (27%) (range 3.7-47.3 cm(3)) and 4.1 cm(3) (1.1-10.1 cm(3)) at 1 week and 6 months, respectively. The cell kill volume was estimated to be 20.5+/-7.4 cm(3) and correlated significantly with the size assessed by MRI at 1 week (r=0.8; p=0.002) and 6 months (r=0.69; p=0.05). At 6 months, the mean decrease in prostate volume was 20.1 cm(3) (p<0.0001). The microstructure of the prostate expressed as the apparent diffusion coefficient was shown to have a strong influence on the treatment process. All patients (n=12) were catheter-free at 6 months. Another patient experienced persistent obstruction and underwent transurethral resection of the prostate.


CONCLUSIONS
Coretherm microwave treatment leads to significant intraprostatic necrosis, which is detectable with MRI even 6 months after the treatment. Diffusion-weighted MRI is capable of identifying structural features of the prostate that can predict the length of treatment and the amount of energy needed.
Vesely
Stepan
S
Department of Urology, Sahlgrenska University Hospital, Göteborg, Sweden.
Müller
Markus
M
Knutson
Tomas
T
Peeker
Ralph
R
Hellström
Mikael
M
Dahlstrand
Christer
C
D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009929:Organ Size; D011237:Predictive Value of Tests; D011470:Prostatic Hyperplasia / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery*; D020127:Recovery of Function; D013997:Time Factors; D020728:Transurethral Resection of Prostate; D016896:Treatment Outcome; D014554:Urination / Q000502:physiology