The Evolution of Laser Therapy in the Treatment of Benign Prostatic Hyperplasia

ILC in the Treatment of BPH

ILC IN THE TREATMENT OF BPH The Evolution of Laser Therapy in the Treatment of Benign Prostatic Hyperplasia Muta M. Issa, MD, FACS, MBA Department of Urology, Emory University School of Medicine and Atlanta Veterans Affairs Medical Center, Atlanta, GA The 2 basic principles of laser therapy for benign prostatic hyperplasia (BPH), based on the final tissue effect, are laser vaporization and laser coagulation. In laser vaporization techniques, higher-density laser thermal energy is used; effects range from complete tissue vaporization to incision, resection, or enucleation of the obstructing prostatic tissue. Interstitial laser coagulation (ILC) requires lower therapeutic temperatures. The urethral preservation and lack of tissue evaporation/resection with ILC make this treatment different from conventional transurethral free-beam laser prostatectomy. The Indigo® Optima Laser treatment system is the most widely used ILC system. Unlike other BPH laser therapies, Indigo ILC can be satisfactorily performed using pure local anesthesia in an office or outpatient setting. Favorable treatment outcomes are seen in a large percentage of patients, with minimal adverse events. Such favorable results depend on proper surgical technique and operator experience. [Rev Urol. 2005;7(suppl 9):S15-S22] © 2005 MedReviews, LLC Key words: Benign prostatic hyperplasia • Laser therapy • Vaporization • Resection • Enucleation • Incision • Interstitial laser coagulation • Indigo® Optima Laser raditionally, the urologist’s approach to the management of benign prostatic hyperplasia (BPH) was limited. Patients were initially administered medical therapy (namely
-adrenergic blockers), and when treatment failed they were advised to undergo surgery. Surgical therapy centered on a single procedure, transurethral resection of the prostate (TURP). Indeed, TURP remained the most effective endoscopic surgical treatment for BPH. However, its risks, T VOL. 7 SUPPL. 9 2005 REVIEWS IN UROLOGY S15 Laser Therapy for BPH continued morbidity profile, inconvenience, and recovery time left much to be desired from the patient’s and clinician’s perspectives. Clearly, a wide gap existed between simple medical therapy on the one hand and TURP on the other. This wide gap, coupled with the need for simpler, less morbid alternatives to TURP, led to the emergence of various less invasive thermotherapies, such as transurethral microwave therapy (TUMT), transurethral needle ablation (TUNA), and interstitial laser coagulation (ILC), as well as other less invasive laser surgeries. What Is a LASER? LASER is an acronym for light amplification by stimulated emission of radiation; common usage today is to use the word as a noun—laser—rather than as an acronym. Laser is a type of electromagnetic radiation. The electromagnetic spectrum also includes radio waves, microwaves, infrared radiation, visible light, ultraviolet rays, x-rays, and gamma rays. All these forms of electromagnetic radiation are fundamentally similar, in that they travel at the speed of light (186,000 miles/s). The difference between them is their wavelength and energy; the shorter the wavelength, the higher the energy. Radio waves have the longest wavelength (tens to hundreds of meters) and the lowest energy. For example, an FM radio station at 100 MHz on the radio dial uses a wavelength of approximately 3 meters. An AM station at 750 kHz on the radio dial uses a wavelength of approximately 400 meters. On the other hand, gamma rays have the shortest wavelengths (less than 1 trillionth [ie,  1012] of a meter) and the highest energy. Lasers used in urology have wavelengths in the range of 400 to 10,000 nm and have been mainly used for the treatment of BPH and stones. S16 VOL. 7 SUPPL. 9 2005 Principles of Laser Therapy for BPH There are 2 basic principles of laser therapy for BPH. These are determined by the final tissue effect (ie, what the laser does to the tissue). The 2 principles are laser coagulation and laser vaporization. In laser coagulation, relatively lowdensity laser thermal energy is used to produce tissue coagulative necrosis, with a potential for delayed anatomical debulking. Clinically significant anatomical debulking occurs only if the tissue is allowed to slough, which takes place when the prostatic urothelium is involved in the process. Preservation and protection of the prostatic urothelium from laser thermal damage prevents tissue sloughing. For laser vaporization, higher-density laser thermal energy is used. This high energy raises the tissue temperature to several hundred degrees Celsius, causing its vaporization. Additionally, various degrees of coagulation necrosis take place in the adjacent residual tissue. This principle is used in different ways to achieve a variety of objectives, depending on the amount and site of tissue vaporization. These range from complete tissue vaporization to incision, resection, or enucleation of the obstructing prostatic tissue. Irrespective of the technique used, the final common result is “opening” (ie, anatomical deobstruction) of the prostatic urethra. Description and Historical Perspective of Laser Therapy for BPH Although the 2 principles (coagulation and vaporization) of laser prostate procedures are simple, the nomenclature, acronyms, and surgical techniques associated with them can be confusing. Many urologists, for simplicity, refer to all types of laser therapy of the prostate as “laser REVIEWS IN UROLOGY prostatectomy,” despite the fact that in many of these therapies no prostate tissue is physically removed. Visual Laser Ablation of the Prostate Visual laser ablation of the prostate (VLAP) is based on the principle of laser coagulation. It was the original technique described for laser prostatectomy.1 Other names given to this procedure include endoscopic laser ablation of the prostate, and side-fire laser prostatectomy; however, these terms are not commonly used. During VLAP, laser energy is delivered to the prostate gland with a side-firing, noncontact, free-beam laser. The most widely used laser energy is neodymium/yttrium-aluminum garnet (Nd:YAG), which has a wavelength of 1064 nm. The prostate is treated with 1 or 2 sets of 4-quadrant sites, depending on the size of the prostate and the length of the prostatic urethra.1,2 The ideal technique, number of treatment sites, wattage power, and duration remain topics of debate. Irrespective of the technique, the final result is coagulative necrosis of the prostatic urethra and adjacent inner prostatic tissue. The obstructive tissue then starts to slough during the ensuing 4 to 8 postoperative weeks, leading to an open or patent prostatic urethra (Figure 1). The anesthesia requirement is similar to that for TURP, in that they both require general or spinal anesthesia. Despite the initial favorable reports, VLAP struggled to maintain its momentum owing to the procedure’s “stormy” postoperative course of prolonged irritative voiding symptoms and urinary retention, which lasted for weeks and sometimes months. Variations in the technique, wattage power, number of treatment sites, and duration were suggested but did not significantly improve this postoperative course. As time went by, the bother and distress Laser Therapy for BPH Bladder Prostate Urethra Figure 1. Visual laser ablation of the prostate. experienced by patients soon persuaded urologists to tame their enthusiasm for this procedure. An important lesson was learned: thermal coagulative necrosis of the prostatic urethra is associated with delayed sloughing and an unacceptable recovery course. This lesson later became the basis for the newer techniques of laser prostatectomy discussed below. Laserscope, San Jose, CA).3-5 This is a noncontact, side-firing laser characterized by its green, 532-nm-wavelength emission. The tissue effect of the KTP laser is different from that of Nd:YAG. The strong absorption of the KTP laser energy by hemoglobin and its minimal absorption by water prevents it from penetrating deep into the tissue, thus the energy gets An important lesson was learned: thermal coagulative necrosis of the prostatic urethra is associated with delayed sloughing and an unacceptable recovery course. Laser Vaporization of the Prostate In laser vaporization, high laser energy (and energy density) is delivered to the obstructing prostatic adenoma, causing the tissue to vaporize. The laser energy can be delivered with a specially designed contact or noncontact laser fiber. The technique involves slowly dragging the tip of the laser fiber along the prostatic urethra from the bladder neck to the level of the verumontanum to create a furrow of evaporated tissue. The process is repeated to create multiple furrows along the prostatic urethra, resulting in a patent bladder outlet (Figure 2). The technique is similar to electrovaporization of the prostate with a roller ball. The latest version of this technique is the high-power potassium-titanylphosphate (KTP) laser (GreenLight; concentrated into the superficial tissue (depth of 1 to 2 mm). This high energy density causes rapid vaporization of the superficial tissue, with a minimal rim (2 mm) of coagulation. The main advantage of laser vaporization over VLAP is an immediate TUR-like defect of the prostatic urethra, resulting in shorter duration of Foley catheterization in the initial postoperative period. Laser Resection of the Prostate Laser resection is based on the principle of laser vaporization. Holmium: YAG is the most widely used laser for this technique. The procedure is often referred to by the acronym HoLRP (holmium laser resection of prostate). The energy is delivered to the prostate through an end-firing 0.55-mm laser fiber. In contrast to conventional laser vaporization of the prostate, the procedure does not completely vaporize the tissue. Instead, the energy is directed such that tissue is resected by vaporizing/incising pieces from the prostate. The obstructing prostatic lobes are resected into multiple small prostate chips that fall into the bladder, similar to standard electrocautery TURP (Figure 3). Relatively small prostates can be resected into chips small enough to be retrieved from the bladder through a standard resectoscope. Larger prostates take significantly more time to resect, making them less suitable for this method. Like laser vaporization, the main advantage of laser resection over VLAP is an immediate anatomical patency of the prostatic urethra, resulting in shorter duration of Foley catheterization and higher peak flow rates in the initial postoperative period.6-11 Laser Enucleation of the Prostate (with Tissue Morcellation) Laser enucleation is similar to laser resection of the prostate in that it is based on the principle of tissue vaporization with a contact bare-tip Figure 2. Laser vaporization of the prostate. Bladder Prostate Urethra VOL. 7 SUPPL. 9 2005 REVIEWS IN UROLOGY S17 Laser Therapy for BPH continued Bladder Prostate Urethra Figure 3. Laser resection of the prostate. Bladder Prostate Urethra Figure 4. Laser enucleation of the prostate. laser fiber. However, instead of the prostatic lobes being resected into small chips, the entire lobes are enucleated intact from the prostatic capsule (Figure 4). The challenge then is to remove the intact prostatic lobes from inside the bladder. Although this can be done with a mechanical tissue morcellator, such morcellation takes considerable time, and the devices are not readily available. Laser Incision of the Prostate Laser incision is based on the principle of tissue vaporization, in which a contact-tip laser fiber is used to deliver high energy along the prostatic urethra, causing a linear tract of tissue vaporization (ie, an incision) (Figure 5). The procedure simulates conventional electrocautery transurethral incision of the prostate (TUIP). Like conventional TUIP, laser incision of the prostate is an efficacious treatment for BPH when performed on relatively small glands ( 30 g). Advocates for this procedure claim better hemostasis with laser incision than with standard electrocautery S18 VOL. 7 SUPPL. 9 2005 TUIP. In my opinion, the difference might not be clinically significant, especially when a hemostatic electrocautery setting is used, that is, low wattage [60–80 W], “blend” mode. The “blend” mode combines cutting and coagulation properties to allow for better hemostasis. One advantage is the lower incidence of postoperative Foley catheterization. Cornford and colleagues12 reported only a 3% rate of Foley catheterization after holmium:YAG laser incision of the prostate in 100 patients. To date, this is the lowest rate of postoperative urinary retention seen after any surgical therapy for BPH. Figure 5. Laser incision of the prostate. Bladder Prostate REVIEWS IN UROLOGY Urethra Interstitial Laser Coagulation Interstitial laser coagulation (ILC) is a minimally invasive thermal therapy that achieves intraprostatic thermal tissue coagulation at a temperature of 85°C and attempts to preserve the prostatic urethra. The lower therapeutic temperatures, the urethral preservation, and lack of tissue evaporation/resection make ILC different from conventional (original) transurethral free-beam laser prostatectomy, despite its “laser” name. Therefore, ILC is better categorized as a minimally invasive thermal therapy, along the lines of microwave, radiofrequency, and high-intensity focused ultrasound therapies. Various other terms are used in the literature to describe the ILC procedure. These include interstitial laser thermal therapy, interstitial thermal therapy, interstitial laser therapy, laser-induced thermal therapy, and laser-delivered interstitial therapy. Indigo® Optima Laser Treatment System The Indigo® Optima Laser Treatment System (Ethicon Endo-Surgery, Cincinnati, OH) is the most widely used ILC system. The Indigo® system consists of a portable laser generator (with a specifically programmed treatment protocol) (Figure 6) and a laser fiber. Its diode laser generator uses a diode pump source and galliumaluminum-arsenide as a lasing medium to generate an 830-nm-wavelength Laser Therapy for BPH less energy in the form of heat during the process of creating the laser beam, which allows better utilization of the energy. Therefore, and in contrast to conventional lasers, the Indigo diode laser does not require high-energy electric wall outlets and cumbersome, noisy internal cooling devices. This allows its generator to be conveniently portable (small size and light weight) and less expensive. The Indigo diode laser generator model is briefcase sized and weighs approximately 13 kg (approximately 28 lb), Figure 6. Indigo® Optima Laser Treatment System (laser generator and laser fiber). Photograph courtesy of Ethicon Endo-Surgery, Inc. laser emission with a power range of 2 to 20 W. With a diode laser generator, the laser beam is created in a different fashion from that of a conventional non-diode laser generator. In the diode principle, semiconductor material is used in a device called a positive-negative junction (PN-junction). Two types of semiconductors, one doped with atoms deficient in electrons and the other doped with atoms having excessive electrons, are used. (“Doping” is the term used to describe the process of attaching such atoms to the semiconductor material.) When energy is applied in a certain way across the PN-junction, electrons flow from one side of the semiconductor to the other, generating energy in the form of light. The light energy then goes through the steps of stimulated emission, amplification, and focusing, resulting in a laser beam. This diode principle is also the basis of the solar cell and the light-emitting diode widely seen on digital display panels of instruments. The Indigo® diode laser system is more efficient than conventional non-diode laser generators. It loses changes according to the changes in the emitted light signal amplitude as the tissue temperature changes during treatment. The Indigo® diffuser-tip laser fiber is an optical laser fiber with an outer diameter of 1.8 mm that fits through a standard cystoscope work channel. Its distal end is designed to emit laser energy in a radial (360° angle) fashion along a 1-cm segment located near the tip. The distal tip of the fiber is beveled into a sharp point to allow its insertion, penetration, and advancement into the prostate. The Indigo diode laser does not require high-energy electric wall outlets and cumbersome, noisy internal cooling devices. compared with bulky, heavy conventional laser generators weighing around 100 kg (about 220 lb). In the Indigo® system, the laser energy is transported from the lasing medium to the laser fiber through semiconductor integrated circuits with relatively low energy loss. The generator has a fully automated energy delivery program that continuously adjusts the power to achieve an efficient and smooth rise to the desired intraprostatic temperature (100°C). The generator receives feedback from an optical sensor at the tip of the laser fiber, which monitors intraprostatic temperatures during treatment. It uses the principle of reflectance (blackbody radiation), which calculates tissue temperature Surgical Technique of ILC The patient is placed in the dorsolithotomy position. Local anesthesia is administered, with transperineal or transrectal prostatic block and topical intraurethral lidocaine.13,14 Supplemental sedation can also be used. A standard cystoscope between 19-F and 21-F is used to insert the laser fiber transurethrally into the prostate gland (Figure 7). Laser energy is then delivered in an automated fashion according to the system treatment protocol. With the Indigo® diode laser system, the process of energy delivery is automated through a proprietary feedback tissue temperature monitoring system (tissue adaptive mode). The intraprostatic temperature Figure 7. Interstitial laser coagulation of the prostate. Bladder Prostate Urethra VOL. 7 SUPPL. 9 2005 REVIEWS IN UROLOGY S19 Laser Therapy for BPH continued 110 100 Lesion temperature Temperature °C 90 Thermal ablation lesion (1–2 cm) 80 70 60 50 40 150 seconds 30 Laser fiber Figure 8. Intraprostatic temperature during Indigo interstitial laser coagulation. reaches the target therapeutic temperature (100°C) within a few seconds and is then maintained at that level for the remainder of the 150-second treatment session (Figure 8). The length of the procedure depends on the number of treatment sites (lesions). There is debate regarding the exact number of treatment sites required. Based on dosimetry studies that showed an ILC lesion volume to be 5 to 7 cm3, we perform 4 treatment sticks for prostates smaller than 35 cm3, 6 for prostates of 35 to 50 cm3, and 8 for prostates of 50 to 65 cm3. Others consider this excessive and prefer fewer treatment sticks. The proper technique in performing ILC—in particular, positioning the laser fiber tip within the prostate—is important. Improper positioning of the laser fiber close to the prostatic urethra might cause thermal injury to the prostatic urethra with subsequent increased likelihood of prolonged postoperative Foley catheterization, exacerbation of irritative voiding symptoms, tissue sloughing, and the potential for retrograde ejaculation. Paying careful attention to the proper technique of intraprostatic laser fiber insertion minimizes urethral thermal injury during ILC.15 The objective is to S20 VOL. 7 SUPPL. 9 2005 place the laser fiber deep inside the prostate at a safe distance from the urethra. More consistent urethral preservation is achieved with this technique, resulting in significantly fewer postoperative complications.15 Results of ILC Several studies have shown ILC to be an effective treatment for symptomatic BPH. A review of the world literature on ILC (14 series) included 785 patients with a follow-up of 2 to 12 months.16 Overall improvement in the American Urological Association (AUA) Symptom Score averaged 70% (22.8 to 6.8; n  785), with improvement in individual series ranging between 32% (19.9 to 13.5; n  25) and 92% (31.0 to 2.3; n  48). Similar improvements were found in the peak flow rates, with an average of 98% (8.1 to 16.0 mL/s; n  785) for all the series combined and a range of 35.2% (6.7 to 10.0 mL/s; n  16) to 203% (8.2 to 24.9 mL/s; n  42) for individual series. The retreatment rate ranged from 0% to 15.4% at 12 months’ follow-up. Urinary tract infection is the most common adverse event after ILC. It was reported in 27% to 35% of patients during the early postoperative period. This high incidence is attrib- REVIEWS IN UROLOGY uted to the inconsistent use of antibiotics and to the prolonged duration of bladder catheters in the initial postoperative period. With the use of prophylactic antibiotics, the incidence decreased to 16.5%. In our institution, urinary infection is prevented by use of prophylactic fluoroquinolone antibiotics, which are continued for 5 days after the procedure.15 In these 14 series, irritative voiding symptoms with tissue sloughing were seen in 11% to 12% of patients, significantly less than with conventional free-beam laser prostatectomy. Significant postoperative bleeding and the need for blood transfusion are extremely rare. Transient stress urinary incontinence was reported in a single patient (0.4%) in one series of 239 patients. The potential risk for true urinary incontinence is rare. The combined rate of urethral strictures and bladder neck contractures (scarring) was less than 5% at the 1-year followup. Postoperative erectile sexual dysfunction has not been reported. The incidence of retrograde ejaculation ranged between 3% and 11.9%. Improvements in the technology, as well as increasing experience, continue to improve the results and morbidity profile of ILC. For example, the 10- to 14-day requirement for bladder catheterization seen in the early studies has decreased significantly after improvement in the surgical technique. In particular, the protection of the prostatic urothelium from thermal injury plays an integral role. With proper technique and experience, the duration of Foley catheterization decreased from an average of 13.3 days to 0.5 days.15 The most recent clinical study, a randomized, controlled, multicenter study published in Urology in March 2003, compared ILC with TURP.17 At the 2-year follow-up point, improvement in the AUA Symptom Score was 63% (24.0 to 9.0; n  37) for the ILC Laser Therapy for BPH patients. Likewise, improvement in peak flow rate was 51% (9.2 to 13.9 mL/s; n  37). The retreatment rate was 16%. Postoperative urinary tract infections occurred in 7 (20%) of the ILC patients. There was no negative impact on sexual function, and there were no reported incidences of urinary incontinence, erectile dysfunction, or retrograde ejaculation. Advantages of ILC Compared With Other Laser Procedures The Indigo® laser treatment system has unique characteristics that define it as a minimally invasive thermal therapy rather than as a conventional laser therapy, even though the name suggests the latter. The temperature in the prostate during Indigo® ILC rises at a steady rate and is in line with other thermal therapies (80°C to 100°C) rather than conventional laser therapies (300°C). The generator is compact, portable, and less costly than other laser systems. The laser fiber is small (1.5 mm outer diameter) and easily inserted into the prostate. The Indigo® laser fiber has an enhanced diffuser tip that achieves higher-power tissue density and faster therapeutic tissue coagulation. As a result, the treatment is fast (150 seconds per lesion) and completely automated. This allows the procedure to be performed efficiently and quickly, usually within half an hour. The ability of the procedure to preserve the urethra allows it to be performed with minimal patient discomfort and side effects. Unlike other BPH laser therapies, Indigo® ILC can be satisfactorily performed using pure local anesthesia in an office or outpatient clinic setting.13-15 Favorable treatment outcomes are seen in a large percentage of patients, with minimal adverse events. Such favorable results depend on proper surgical technique and operator experience. 2. References 10. 1. Costello AJ, Bowsher WG, Bolton DM, et al. Laser ablation of the prostate in patients with benign prostatic hyperplasia. Br J Urol. 1992; 69:603-608. 3. 4. 5. 6. 7. 8. 9. 11. Kabalin JN. Laser prostatectomy performed with a right-angle firing Nd:YAG laser fiber at 40 watts power setting. J Urol. 1993;150:95-99. Kuntzman RS, Malek RS, Barrett DM. Highpower potassium-titanyl-phosphate (KTP/532) laser vaporization prostatectomy. Mayo Clin Proc. 1998;73:798-801. Malek RS, Barrett DM, Kuntzman RS. Highpower potassium-titanyl-phosphate (KTP/532) laser vaporization prostatectomy: 24 hours later. Urology. 1998;51:254-256. Malek RS, Barrett DM, Kuntzman RS. High-power potassium-titanyl-phosphate laser vaporization prostatectomy. J Urol. 2000;163:1730-1733. Gilling PJ, Cass CB, Cresswell MD, et al. Holmium laser resection of the prostate: preliminary results of a new method for the treatment of benign prostatic hyperplasia. Urology. 1996; 47:48-51. Gilling PJ, Cass CB, Malcolm A, et al. Holmium laser resection of the prostate versus neodymium:yttrium-aluminum-garnet visual laser ablation of the prostate: a randomized prospective comparison of two techniques for laser prostatectomy. Urology. 1998;51:573-577. Gilling PJ, Mackey M, Cresswell M, et al. Holmium laser versus transurethral resection of the prostate: a randomized prospective trial with 1-year follow-up. J Urol. 1999;162:1640-1644. Matsuoka K, Iida S, Tomiyasu K, et al. Holmium laser resection of the prostate. J Endourol. 1998;12:279-282. Matsuoka K, Iida S, Tomiyasu K, et al. Transurethral holmium laser resection of the prostate. J Urol. 2000;163:515-518. Chilton CP, Mundy IP, Wiseman O. Results of holmium laser resection of the prostate for Main Points • There are 2 basic principles of laser therapy for benign prostatic hyperplasia, based on the final tissue effect: laser vaporization and laser coagulation. • In laser vaporization, high-density laser thermal energy raises the tissue temperature to several hundred degrees Celsius; irrespective of the specific technique used, the final common result of vaporization-based therapy is the “opening” of the prostatic urethra. • Interstitial laser coagulation (ILC) requires lower therapeutic temperatures than vaporization-based therapies; the urethral preservation and lack of tissue evaporation/resection with ILC make this treatment different from conventional transurethral free-beam laser prostatectomy. • The proper technique in performing ILC—in particular, the positioning of the laser fiber tip within the prostate—is important; the objective is to place the laser fiber deep inside the prostate at a safe distance from the urethra. Urethral preservation results in significantly fewer postoperative complications. • A review of the world literature on ILC (14 series) showed that overall improvement in the American Urological Association Symptom Score averaged 70%; similar improvements were found in the peak flow rates, with an average of 98% for all the series combined. • The Indigo® Optima Laser Treatment System is the most widely used ILC system. The Indigo® generator is compact, portable, and less costly than other laser systems. • The Indigo® laser fiber is small and easily inserted into the prostate; it has an enhanced diffuser tip that achieves higher-power tissue density and faster therapeutic tissue coagulation. The treatment is fast (1.5 minutes per session) and completely automated. VOL. 7 SUPPL. 9 2005 REVIEWS IN UROLOGY S21 Laser Therapy for BPH continued 12. 13. S22 benign prostatic hyperplasia. J Endourol. 2000; 14:533-534. Cornford PA, Biyani CS, Powell CS. Transurethral incision of the prostate using the holmium:YAG laser: a catheterless procedure. J Urol. 1998;159: 1229-1231. Issa MM, Ritenour C, Greenberger M, et al. The prostate block for outpatient prostate surgery. World J Urol. 1998;16:378-383. VOL. 7 SUPPL. 9 2005 14. 15. 16. Cohen MS, Steiner MS. Interstitial laser coagulation techniques: local anesthesia techniques. World J Urol. 2000;18(suppl 1):S18-S21. Issa MM, Townsend M, Jiminez VK, et al. A new technique of intra prostatic fiber placement to minimize thermal injury to prostatic urothelium during Indigo interstitial thermal therapy. Urology. 1998;51:105-110. Muschter R. Interstitial laser therapy of benign REVIEWS IN UROLOGY 17. prostatic hyperplasia. In: Graham SD Jr, Glenn JF, eds. Glenn’s Urological Surgery, 5th ed. Philadelphia: Lippincott-Raven; 1998:11111117. Kursh ED, Concepcion R, Chan S, et al. Interstitial laser coagulation versus transurethral prostate resection for treating benign prostatic obstruction: a randomized trial with 2-year follow-up. Urology. 2003;61:573-578.