Does transurethral microwave thermotherapy have a different effect on prostate cancer than on benign or hyperplastic tissue?

Objectives. Transurethral microwave thermotherapy is useful for the treatme nt of benign prostatic hyperplasia, but its effect on cancer is not documen ted. We analyzed the pathologic changes occurring after microwave thermothe rapy in whole mount radical prostatectomy specimens from patients with canc er. Methods. Nine patients scheduled for radical prostatectomy for clinically l ocalized prostate cancer were treated with transurethral microwave thermoth erapy (Urologix Targis System). Patients ranged in age from 64 to 72 years (mean 68). Seven patients underwent prostatectomy 4 to 90 hours after therm otherapy, and 2 other patients underwent prostatectomy 12 months after ther motherapy. Whole mount totally embedded prostates were mapped for necrosis and cancer, and the volume of each was measured by the grid method. 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 devital ization without significant inflammation. Necrosis involved contiguous area s of benign epithelium, stroma, and cancer without skip areas. The mean vol ume 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 w as symmetric around the urethra in 6 of 7 cases. Urethral dilation was obse rved 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 mo nths after thermotherapy had a mean weight of 88 g (55 and 121 g, respectiv ely). Each showed periurethral fibrosis, nonspecific chronic inflammation, and squamous metaplasia of the urothelium, The mean volume of necrosis rema ining 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 b enign prostate and cancer contiguous to the urethra, resulting in hemorrhag ic necrosis with minimal damage to the urethra. There was no apparent diffe rential morphologic sensitivity of benign prostatic tissue, hyperplastic ti ssue, or cancer to thermotherapy. UROLOGY 54: 67-72, 1999. (C) 1999, Elsevi er Science Inc.