High-Power Potassium Titanyl Phosphate Laser Vaporization Prostatectomy

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High-Power Potassium Titanyl Phosphate Laser Vaporization Prostatectomy RANDALL

S. KUNTZMAN, M.D., REZA S. MALEK, M.D., AND DAVID M.

patients with symptomatic BPH who ranged in age from 52 to 80 years, outpatient KTP laser prostatectomy yielded significantly increased mean peak urinary flow rates (from 8.0 mLis preoperatively to 19.4 mLis within 24 hours after the procedure). No patient had hematuria, dysuria, or incontinence after removal of the catheter, and no patient required recatheterization. One patient, however, had urgency, and two other patients became febrile during the 24-hour observation period. Overall, KTP laser vaporization prostatectomy can provide immediate relief from obstructive symptoms of BPH and is not associated with dysuria. Mayo Clin Proc 1998;73:798-801

In a search for potential therapeutic strategies for benign prostatic hyperplasia (BPH) that would be associated with less morbidity than transurethral resection of the prostate, various types of laser prostatectomy have been used. Although the neodymium:yttrium-aluminum-garnet (Nd:YAG) laser allows performance of prostatectomy in an almost bloodless field and without absorption of irrigant, the remaining necrotic tissue causes bladder outlet obstruction and related symptoms for 5 to 7 days after treatment. In contrast, the potassium titanyl phosphate (KTP) laser has been found to vaporize tissue with minimal coagulation of the underlying structures. With use of the KTP laser, heat is concentrated into a small volume, the tissue is ablated by rapid vaporization of cellular water, and a 2-mm rim of coagulated tissue is left. After favorable results were obtained in studies of canine prostates and human cadavers, we implemented clinical use of 60-W KTP laser prostatectomy in selected patients. In 10

AUA =American Urological Association; BPH =benign prostatic hyperplasia; KTP = potassium titanyl phosphate; Nd:YAG = neodymium:yttrium-aluminum·garnet; TURP = transurethral resection of the prostate

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enign prostatic hyperplasia (BPH) is a nonmalignant neoplasm of the prostatic epithelial and stromal tissue that causes enlargement of the prostate gland and may result in bladder outlet obstruction. BPH is common among older men in the United States and worldwide. Most frequently, obstructive symptoms of BPH occur between the ages of 65 and 70 years; approximately 65% of men in this age-group have prostatic enlargement from hyperplasia. 1-3 During the 50 years since its introduction, transurethral resection of the prostate (TURP) has become the most widely used surgical therapy for BPH. During TURP, the bladder must be continually irrigated with a nonconductive isosmotic solution (1.5% glycine) to keep the surgical field from being obscured by blood and to minimize the deleterious effects of fluid absorption. Because patients may lose a substantial amount of blood and irrigant may be forced into open prostatic venous sinuses during the procedure, TURP is associated with an operative mortality of 0.2% and a perioperative morbidity of 24.9% (6.9% intraoperative plus 18% postoperative).' In addition, patients who have BPH are often elderly, and 77% have at least one major

preexisting medical condition that increases their medical risk." Accordingly, an aggressive search for alternative medical and less morbid surgical therapies for BPH has been initiated.

EXPERIMENTAL BACKGROUND Neodymium:yttrium-aluminum-garnet (Nd: YAG) laser coagulation prostatectomy is an effective treatment for bladder outlet obstruction due to BPH, and its efficacy is comparable to that of transurethral electroresection of the prostate>" Unlike TURP, the procedure is almost bloodless and without absorption of irrigant; thus, the operative risks associated with Nd:YAG laser prostatectomy are considerably reduced. For 5 to 7 days after treatment with the Nd:YAG laser, however, the remaining necrotic material causes bladder outlet obstruction. Voiding function improves gradually after removal of the urethral catheter, and the sloughing of necrotic tissue during a period of weeks is accompanied by troublesome dysuria in some patients. The potassium titanyl phosphate (KTP) laser with power settings of up to 40 W has been used in urologic practice since 1986 for treatment of urothelial tumors, strictures, bladder neck contracture, penile cancer, and condyloma. More recently, it has also been used for transurethral incision of the prostate and in treating the median and lateral prostatic lobes as an adjunct to Nd:YAG laser coagulation prostatectomy.U':" Impressively, most

From the Department of Urology, Mayo Clinic Rochester, Rochester, Minnesota. Address reprint requests to Dr. R. S. Malek, Department of Urology, Mayo Clinic Rochester, 200 First Street SW, Rochester, MN 55905.

Mayo Clin Proc 1998;73:798-801

BARRETT, M.D.

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© 1998 Mayo Foundation for Medical Education and Research

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Mayo Clin Proc, August 1998, Vol 73

patients who underwent concurrent adjunctive KTP laser vaporization of the aggressively Nd:YAG-coagulated prostate were free of a catheter within 3 days, in comparison with those who underwent Nd:YAG laser coagulation prostatectomy only and subsequently required at least 5 days of catheterization-a statistically significant difference in outcome and patient comfort. II In these capacities, the KTP laser is valued for its ability to vaporize tissue with minimal coagulation of the underlying structures, a feature suggesting that the KTP laser may be an optimal tool for the immediate transurethral removal of prostatic tissue in a precise manner and in a hemostatic environment without causing deep coagulation. Our purpose in evaluating the KTP laser was to attempt to find a prostatectomy technique that would achieve removal of tissue at the time of the operative procedure, similar to electrosurgical TURP, and yet would be hemostatic and free from irrigant absorption, like Nd:YAG prostatectomy. The dissimilar absorption patterns of the 532-nm wavelength KTP laser and the I,064-nm Nd:YAG laser produce considerably different tissue effects. Nd:YAG laser energy is absorbed by cellular proteins and penetrates up to 7 mm into tissue. Because the laser energy affects such a large volume of tissue, heating occurs relatively slowly, and the result is coagulation and desiccation of both the irradiated and the surrounding tissues. In contrast, KTP laser energy is strongly absorbed by hemoglobin and penetrates only 1 to 2 mm of tissue. With use of the KTP laser, heat is concentrated into a small volume, the tissue is ablated by rapid vaporization of cellular water, and only a 2-mm rim of coagulated tissue is left. Surprisingly, although the effects of the Nd:YAG laser on prostatic tissue had been extensively documented in animals, those of the KTP laser, despite its widespread clinical use, had not been investigated. Therefore, the functional, pathologic, and histologic effects of KTP laser vaporization, Nd:YAG laser coagulation, and Nd:YAG laser vaporization of the canine prostate were recently compared in a prospective, randomized trial 'at Mayo Clinic Rochester." This study showed that 38-W KTP laser vaporization prostatectomy provided hemostasis and freedom from irrigant absorption, similar to the results obtained with Nd:YAG laser coagulation, but also removed tissue at the time of operation (Fig. 1); hence, dogs could void without straining within 24 hours after treatment. The procedure created large prostatic cavities that healed without scar tissue. No dog had a major change in hematocrit, and none was incontinent. In addition, the procedure was technically simple, offered the operator excellent visual control over exactly which tissue was removed and which was left intact, and produced only a 2-mm-thick rim of coagulation. These findings suggested that KTP laser va-

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porization by itself might be useful in the treatment of human BPH.14 Recent advances in laser technology have made a 60-W KTP laser clinically practical. At this power setting, KTP 532-nm laser energy presented the possibility of more rapid vaporization of tissue. The functional, pathologic, and histologic effects of 60-W KTP laser vaporization of the prostate were evaluated in a group of 10 experimental dogs. In addition, two fresh frozen human cadavers were used for performance of 60-W KTP laser prostatectomy, and the results were compared with the effects of 60-W KTP laser on two fresh frozen canine cadaver prostates. IS The 60-W KTP laser allowed technically easy, safe, rapid, and hemostatic removal of the canine prostate tissue in vivo; again, only a 2-mm-thick rim of coagulation was produced. All five animals that were kept alive for 7 weeks were continent, had normal erections, and were free of a catheter within 24 hours postoperatively. Only one dog required recatheterization because of urinary retention; it voided successfully thereafter. Furthermore, no difference was noted in the efficacy of KTP laser vaporization between human and canine cadaver prostates. These findings suggested that KTP laser vaporization could be as effective in living human prostates as it was in living dogs and thus would be a useful, safe, and user-friendly technique in the surgical treatment of human BPH.IS CLINICAL APPLICATIONS On the basis of the foregoing animal studies and the favorable results of 40-W KTP laser vaporization as an adjunct to Nd:YAG laser coagulation prostatectomy, use of 60-W KTP laser prostatectomy has been implemented clinically at our institution. Although the duration of follow-up has been relatively brief, our recently published early results have been promising. Ten men with symptomatic BPH whose ages ranged from 52 to 80 years (mean, 69) underwent physical examination and evaluation of their symptoms, as judged by the American Urological Association (AUA) symptom index, as well as measurement of their peak urinary flow rate and residual urine volume. 16 The size and appearance of the prostate and the status of the bladder were determined by transrectal ultrasonography and cystoscopy, respectively.

Procedures Vaporization was performed with the Laserscope ADD Stat fiber (Laserscope, San Jose, California), which is a 600-llm fiber with a quartz capsule over the 70-degree lateral deflecting quartz element and a spot diameter of 1.2 mm at a distance of 2 mm. The laser fiber was introduced through the lumen of a 22-F continuous-flow Olympus laser cystoscope, and sterile water was used as irrigant.

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KTP Laser Prostatectomy

Mayo Clio Proc, August 1998, Vol 73

Nd:YAG coagulation

Nd:YAG vaporization

KTP vaporization

cavitatio n diameter = :; nun coagulation dep th = lot nun

cavitation diameter =

cavit arion diame ter = .' 0 nun

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coagulation depth = 2 rnm

Fig. 1. Diameter of prostatic cavitation defect in comparison with depth of coagulation 2 days after laser prostatectomy in canines. KTP = potassium titanyl phosphate; Nd:YAG = neodymium:yttrium-aluminum-garnet. (Data from Kuntzman and associates. 14)

The KTP 532-nm laser energy was generated by a prototype Laserscope 800 series very-high-power KTP:YAG laser generator, which delivered 60 W of continuous power. Application of the laser was performed by a free-beam technique, in which the fiber was held 1 to 2 mm away from the tissue, and the lateral lobes were vaporized beginning at the bladder neck. Next, the median lobe was vaporized similarly to the level of the transverse fibers of the bladder neck; however, if the median lobe was large, it was vaporized before the lateral lobes. The endpoint was appreciated by the size and appearance of the large TVRP-like cavity thus created and by the diminished efficacy of the vaporization effect at the prostatic capsule. Frequently, prostatic duct calculi were observed being released from their surroundings during the procedure, which was essentially bloodless. Rare bleeding vessels were easily coagulated by application of the laser from a distance of 3 to 4 mm. We did not need to switch to the Nd:YAG laser for coagulation of the vessels in this group of patients, although this option was readily available as an integral part of the generator. Laser application time ranged from 17 to 48 minutes (mean, 29 ± 8), during which 60.8 to 174.6 kJ (mean, 104.6 ± 30) of energy was delivered. 16 All patients had sterile urine preoperatively and received a general anesthetic agent. All 10 patients were treated as outpatients, and a 2-week course of trimethoprim-sulfamethoxazole twice daily was prescribed after the procedure.

Results Ultrasonographically, the volumes of the prostate glands ranged from 22 to 60 mL (mean, 38.4 ± 9.7), and

they all were normal. Prostate-specific antigen values ranged from 0.51 to 5.1 ng/ml, (mean, 2.15 ± 1.5). All 10 patients had normal renal function, and none had any fluid absorption; immediate postoperative serum sodium values ranged from 138 to 140 mEq/L. The patient with the largest prostate in the series (60 mL) lost an estimated 100 mL of blood during the procedure; other patients had clear drainage during and after the operation. None of the Foley catheters needed irrigation, and all were removed the morning after the procedure (in 24 hours or less). 16 Preoperatively, the AVA symptom scores ranged from 16 to 22 (mean, 19.4 ± 2.1). Because of the nature of the questions about the symptoms experienced during the previous month, obtaining a valid AVA symptom score 24 hours postoperatively was not possible. The mean peak urinary flow rate increased significantly from 8.0 ± 1.3 mLI s preoperatively to 19.4 ± 8.4 mLis (142%; P = 0.003) 24 hours after the procedure and approximately 5 hours after removal of the Foley catheter. The mean postvoiding residual urine volume, however, remained essentially unchanged-148 mL preoperatively and 163 mL at 24 hours postoperatively (P = 0.767). This finding was expected because of the relatively limited amount of time allowed for recovery of detrusor function postoperatively. None of the patients had hematuria, dysuria, or urinary incontinence after removal of the catheter, nor did any patient require recatheterization. One patient, however, had urgency, and two other patients became febrile during the observation period of 24 hours without an indwelling catheter. The two febrile patients had sterile urine and blood cultures; pneumonia had developed in one, and the other had a drugrelated fever in reaction to sulfamethoxazole therapy. 16

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Mayo Clin Proc, August 1998, Vol 73

Three patients returned for follow-up 3 months postoperatively. Their mean ADA symptom score decreased from 18.7 to 4.3 (77% improvement), their mean peak urinary flow rate increased from 8.1 to 21.6 mLls (167%), their mean residual urine volume decreased from 161 to 29 mL (82%), and their mean prostate-specific antigen value diminished from 2.46 to 0.93 ng/ml, (62%). All three patients remained sexually potent; however, retrograde ejaculation had developed in twO. 16 CONCLUSION Overall, 60-W KTP laser vaporization prostatectomy is technically easy, user-friendly, and effective in yielding good symptomatic relief and substantial improvement in maximal urinary flow rate in conjunction with excellent hemostasis and minimal perioperative morbidity. Collectively, the animal studies and human clinical trials at Mayo Clinic Rochester have shown that 60-W KTP laser vaporization prostatectomy, by itself, is as safe as but more efficacious than Nd:YAG laser coagulation prostatectomy (with or without adjunctive vaporization with 40-W KTP laser) in providing immediate relief from prostatic obstruction.P" Patients are free of a catheter in less than 24 hours postoperatively and do not experience the troublesome dysuria that usually accompanied Nd: YAG laser prostatectomy. KTP laser prostatectomy has become a part of our routine clinical management for selected patients, and our results to date in more than 40 patients have been remarkable.

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Berry sJ, Coffey OS, Walsh PC, Ewing LL. The development of human benign prostatic hyperplasia with age: J Urol 1984;132:474479

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Lytton B, Emery JM, Harvard BM. The incidence of benign prostatic obstruction. J Urol 1968;99:639-645 Glynn RJ, Campion EW, Bouchard GR, Silbert JE. The development of benign prostatic hyperplasia among volunteers in the Normative Aging Study. Am J Epidemiol 1985;121:78-90 Mebust WK, Holtgrewe HL, Cockett ATK, Peters PC. Transurethral prostatectomy: immediate and postoperative complications; a cooperative study of 13 participating institutions evaluating 3,885 patients. J Urol 1989;141:243-247 Gill Hs, Kaballn IN, Mikus PW. Characterization of tissue effects produced by the Prolase II lateral-firing neodymium:YAG laser fiber in the canine prostate. Lasers Surg Med 1994;15:185-190 Costello AJ, Bowsher WG, Bolton OM, Braslis KG, Burt J. Laser ablation of the prostate in patients with benign prostatic hypertrophy. Br J Urol 1992;69:603-608 Cowles ns III, Kabalin IN, Childs 5, Lepor H, Dixon C, Stein B, et al. A prospective randomized comparison of transurethral resection to visual laser ablation of the prostate for the treatment of benign prostatic hyperplasia. Urology 1995;46:155-160 Malek Rs, Barrett OM, Dilworth JP. Visual laser ablation of the prostate: a preliminary report. Mayo Clin Proc 1995;70:28-32 Kaballn IN, Gill as, Bite G, Wolfe V. Comparative study of laser versus electrocautery prostatic resection: 18-month followup with complex urodynamic assessment. J Urol 1995;153:94-97 Kabalin IN, Bite G, Doll S. Neodymium:YAG laser coagulation prostatectomy: 3 years of experience with 227 patients. J Urol 1996;155:181-185 Kollmorgen TA, Malek Rs, Barrett OM. Laser prostatectomy: two and a half years' experience with aggressive multifocal therapy. Urology 1996;48:217-222 Norris JP, Norris OM, Lee RO, Rubenstein MA. Visual laser ablation of the prostate: clinical experience in 108 patients. J Urol 1993;150:1612-1614 Anson KM, Watson GM, Shah TK, Barnes OG. Laser prostatectomy: our initial experience of a technique in evolution. J Endourol 1993;7:333-336 Kuntzman as, Malek as, Barrett OM, Bostwick OG. Potassiumtitanyl-phosphate laser vaporization of the prostate: a comparative functional and pathologic study in canines. Urology 1996;48:575583 Kuntzman Rs, Malek Rs, Barrett OM, Bostwick OG. High-power(60watt) potassium-titanyl-phosphate laser vaporization prostatectomy in Urology living canines and in human and canine cadavers. 1997;49:703-708 Malek Rs, Barrett OM, Kuntzman Rs. High-power potassium-titanylphosphate (KTP/532) laser vaporization prostatectomy: 24 hours later. Urology 1998;51:254-256

End of Symposium on Benign Prostatic Hyperplasia, Part III. Part IV wi II appear in the September issue.

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