Interstitial thermal therapy in patients with localized prostate cancer: histologic analysis

Abstract Objectives. To examine, by way of histologic examination, the destruction of excised prostate glands treated with thermal ablation. Thermal ablation treatment with permanently implanted temperature self-regulating rods is being used in the treatment of localized prostate cancer. Methods. Four patients with biopsy-proven prostate cancer, who had been scheduled for routine radical prostatectomy with a gland size of less than 70 g, Gleason sum of 7 or less, and prostate-specific antigen values less than 10.0 ng/mL, were implanted with 70°C rods under ultrasound and fluoroscopic control. The patients were then given multiple thermal treatments. Glands were removed and histologically analyzed to access the thermal destruction. Results. Histologic examination revealed confluent thermal destruction within the rod array when the rods were placed end-to-end and no farther than 1 cm apart. Little necrosis was seen outside the array. To ensure the necessary destruction, the rods must be placed at the capsule, including posteriorly near the rectum. The results indicated that energy levels greater than 40 W-min/g of tissue should be used. This can be achieved by implanting 1.5 rods/g of prostate and treating the patient for 60 minutes. In 3 of the 4 patients, no residual cancer was found in the gland after thermal treatment. Conclusions. Histologic examination has aided in determining the implant density and treatment time and, therefore, the necessary energy, for adequate necrosis. The technique demonstrates the ability to destroy the prostate adequately, including tissue at the capsule. This new procedure appears promising in the treatment of localized prostate cancer.