Histopathology of benign prostatic hyperplasia after failure of hyperthermia treatment.

We have used a fine morphometric method to evaluate hyperplastic prostate tissue after treatment by local hyperthermia and compare it with untreated specimens. Local hyperthermia was delivered to the prostate gland by a transrectal applicator using microwaves at 915 MHz. Prostatic tissue was obtained from 13 patients who had completed a course of local hyperthermia treatment and who underwent prostatectomy 3 to 12 months later because the treatment had failed. Prostatic tissue from 9 patients who had undergone prostatectomy with no previous treatment served as a control. A significant reduction in the volume fraction of fibrous tissue was found in the study group (37%) compared with the general population (48%). No inter-group difference was observed in the volume fractions of vascular or glandular tissue. We suggest that the difference observed in the fibrous elements may be the reason for the failure of treatment and that the histological composition of the diseased gland may, therefore, be a key factor in determining the outcome.