Anterior perirectal fat tissue thickness is a strong predictor of recurrence after high-intensity focused ultrasound for prostate cancer.
OBJECTIVE
To evaluate if and why obesity affects the clinical outcome in patients undergoing high-intensity focused ultrasound (HIFU) treatment for prostate cancer (CaP).


METHODS
115 patients who underwent HIFU treatment for localized CaP were categorized as obese, overweight or normal according to body mass index (BMI). The thickness of the anterior perirectal fat tissue (APFT) was measured by transrectal ultrasonography. Treatment was considered to have failed in the case of biochemical failure according to the Phoenix definition, positive follow-up biopsy or initiation of salvage therapy. Cox proportional hazards analyses were used to identify possible predictors for disease free survival (DFS), and an experimental fat tissue model was made to evaluate the ablation effect at the target tissue.


RESULTS
According to the classification by the Western Pacific Regional Office of WHO, 43 patients were of normal weight, 24 were overweight and 48 were obese. The BMI groups did not differ in Gleason score, prostate-specific antigen level at diagnosis or clinical stage. There were, however, significant correlations between BMI and prostate-specific antigen nadir (P < 0.001), and BMI and APFT thickness (P < 0.01). Multivariate analyses showed that BMI fails to be an independent predictor of DFS when APFT (P < 0.0001) is included as a variable.


CONCLUSIONS
Our results suggest that APFT thickness, for which obesity could be a useful surrogate, might represent the causative factor for poor clinical outcome after transrectal HIFU treatment for CaP.
Sumitomo
Makoto
M
Department of Urology, National Defense Medical College, Tokorozawa, Saitama, Japan. mh712sumitomo@ybb.ne.jp
Asakuma
Junichi
J
Yoshii
Hidehiko
H
Sato
Akinori
A
Horiguchi
Akio
A
Ito
Keiichi
K
Nagakura
Kazuhiko
K
Asano
Tomohiko
T
D000273:Adipose Tissue / Q000473:pathology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000453:epidemiology*; D009765:Obesity / Q000150:complications*; D011379:Prognosis; D011471:Prostatic Neoplasms / Q000150:complications / Q000453:epidemiology* / Q000601:surgery*; D012007:Rectum / Q000473:pathology; D036761:Ultrasound, High-Intensity Focused, Transrectal