RESULTS: Pathologic stages were T2a (n = 4), T2b (n = 4), and T3b (n = 1). The prostates from patients who underwent radical
prostatectomy within 4 to 90 hours of
thermotherapy had a mean prostate weight of 47.4 g (range 19.5 to 70.3). Each consistently showed hemorrhagic
necrosis and tissue devitalization without significant
inflammation.
Necrosis involved contiguous areas of benign epithelium, stroma, and
cancer without skip areas. The mean volume of
necrosis was 8.8 cc (range 1.4 to 17.8), and the mean percentage of the prostate involved by
necrosis was 22% (range 3% to 39%). The
necrosis was symmetric around the urethra in 6 of 7 cases. Urethral dilation was observed in 3 patients, and the mean maximum radial distance of necrotic tissue was 1.4 cm (range 0.6 to 1.8). Necrotic change was noted in 80% to 100% of the volume of
cancer in 4 cases, 40% to 60% in 2 cases, and 5% in 1 case. The prostates from the 2 patients who underwent radical
prostatectomy 12 months after
thermotherapy had a mean weight of 88 g (55 and 121 g, respectively). Each showed periurethral
fibrosis, nonspecific chronic
inflammation, and squamous
metaplasia of the urothelium. The mean volume of
necrosis remaining was 0.2 cc. The mean percentage of the prostate involved by
necrosis 1 year after
thermotherapy was less than 1%. There was some reabsorption of dead tissue. The mean maximum radial distance of the necrotic tissue was 0.4 cm (0.2 and 0.7 cm, respectively). The prostatic urethra had viable and partially denuded urothelium in all cases.
CONCLUSIONS: Microwave
thermotherapy is clinically useful for ablation of benign prostate and
cancer contiguous to the urethra, resulting in hemorrhagic
necrosis with minimal damage to the urethra. There was no apparent differential morphologic sensitivity of benign prostatic tissue, hyperplastic tissue, or
cancer to
thermotherapy.