Technique and results of interstitial laser coagulation

Summary

By use of thermal “ablation” techniques to apply heat to the prostate from the urethra, the coagulation volume is limited by the limited penetration depth of suitable radiation sources, e.g., lasers, and by heat conduction. Secondarily, the coagulated tissue is removed by sloughing. Interstitial heat application was expected to overcome these problems. Our initial in vitro and animal studies using different light guides for interstitial Nd: YAG laser radiation showed that small, carbonized lesions were created by bare fibers, whereas large, homogeneous coagulation zones measuring up to 2 cm in diameter were produced by specially designed ITT (interstitial thermotherapy) fibers, which secondarily resulted in marked volume reduction by atrophy. Further experiments using such applicators resulted in an operation technique suitable for clinical routine in the treatment of symptomatic benign prostatic hyperplasia (BPH). These laser applicators are inserted into the prostate either transurethrally through a cystoscope under direct vision or percutaneously from the perineum under transrectal ultrasound guidance. The number of placements depends on the size and configuration of the gland. Radiation parameters were optimized for each system. To avoid charring, relatively low levels of laser power and long radiation periods (e.g., 7 W for 10 min) or power-formatting programs (e.g., stepwise reduction of power from 20 to 7 W for a total radiation time of 3 min) are applied. Beginning in July 1991, more than 350 unselected patients with BPH were treated with interstitial laser coagulation in our department, of whom 239 were followed for at least 1 year. The following changes in mean values were observed: American Urological Association (AUA) score, from 25.4 to 6.1; urinary peak flow rate, from 7.7 to 17.8 ml/s; residual urinary volume, from 151 to 10 ml; and prostate volume, from 47.4 to 29.1 ml. Retreatment was necessary in 9.6% of cases.