Depth of penetration of the neodymium: yttrium-aluminum-garnet laser in the human prostate and clinical results of high-dose laser energy in 50 patients

Summary

We evaluated the treatment of the human prostate with the Nd:YAG laser using a Cytocare Prolase II fiber. We utilized this first in 12 patients prior to radical prostatectomy and then appropriately serially sectioned the prostate to measure the depth of penetration. The studies clearly revealed that 60 W of power and 60 s of pulse duration gave the most consistent depth of penetration in the human prostate model. This depth of penetration averaged 2 cm in the glands that were removed. At the same time there was absolutely no evidence of damage to the neurovascular bundle or to the capsule of the prostate using the above-mentioned dosimetry regime. This study was then transferred to our initial experience in treating 50 patients with benign prostatic hypertrophy and obstructive voiding symptoms. The first 25 patients were also treated with so-called spot radiation of the prostate, whereas the second 25 patients were treated by total photoirradiation of all visible endoscopic tissue. The results reveal that both groups of patients had a fairly highly satisfactory result as measured objectively with American Urological Association (AUA) symptom scores and uroflow studies. In the latter group (photoirradiation of all visible endoscopic tissue) a significantly higher dose of laser energy was utilized and a smaller failure rate was noted on a long-term basis in patients who subsequently came to transurethral resection of the prostate (TURP) because of failure of the laser procedure. At the same time that the patients were treated, all 50 patients underwent multiple random needle biopsies of the peripheral zone of the prostate, and at no time was there any evidence of a laser effect in the capsule of the human prostate from a dosimetry of 60 W and 60 s of pulse duration and total photoirradiation of the entire prostate. Very large doses of energy were used, ranging up to 110,000 J per case. It is our impression that the 60-W/60-s protocol will consistently yield the best results in terms of success of laser prostatectomy as measured objectively with uroflow and AUA symptom score as well as providing total safety in term of the absence of damage to the capsule of the prostate despite photoirradiation of all visible viable tissue at high total doses of energy.