Lasers in Urology. An Evidence-Based Approach to Choosing the Right Tool

Transcription

1 Lasers in Urology An Evidence-Based Approach to Choosing the Right Tool Today medical lasers and specifically designed optical fibers offer benefits in a variety of surgical applications. Selecting the right tool for the job requires an understanding of the advantages and disadvantages of each laser technology. Potassium-Titanyl-Phosphate (KTP) and Holmium:Yttrium-Aluminum- Garnet (Ho:YAG) are the two primary lasers used in modern urology, addressing two of the most common urologic conditions, BPH and Stones. Clinical evidence reveals KTP as the laser wavelength of choice for the treatment of BPH, while Holmium is the laser of choice for the treatment of Stones. With more than 75 training sites in the United States and more than 500 urologists performing GreenLight procedures, GreenLight PVP is the first procedure to seriously challenge the Gold Standard TURP.

2 About the Physics Figure 1 identifies the absorption characteristics of different laser wavelengths. Understanding these differences is key to choosing the right laser for the right indication. Optical Penetration Depth Optical depth of penetration should be assessed in tissue and irrigation fluid to determine both the coagulation zone and the efficiency of energy delivery. High absorption in hemoglobin limits penetration of the KTP laser beam to a depth of only 0.8mm (optical penetration depth) [Jac92]. Figure 1: Absorption pattern of water and oxyhemoglobin Vaporization occurs from within the tissue where vapor bubbles form and burst the collagen matrix [Te04a, Mal04b]. Heat remaining in the tissue induces a coagulation zone of only a 1-2 mm thickness sufficient to achieve hemostasis and small enough to limit edema formation [Kun97]. PVP treatment of patients on anti-coagulants is feasible due to the hemostatic properties of the KTP laser [Hai03]. Interaction of the Ho:YAG laser with tissue is very superficial due to the extremely small depth of penetration of only 0.4 mm [Gil96]. The tissue volume heated by the laser is very small, which limits vaporization speed, coagulation depth and hemostasis [Te04a]. To our knowledge, treatment of patients on anti-coagulants with HoLAP has not been documented in published literature.. Wavelengths and Optical Penetration Depths Laser Wavelength (nm) Water Tissue (mm) Ho:YAG 2,100 Optical penetration depth 0.4 mm 0.4 KTP m 0.8 One Technique GreenLight PV delivers a "one technique" approach for all gland sizes and patient profiles. Clinical studies at top academic institutions around the world have demonstrated the safety and efficacy of GreenLight PVP for patients on anti-coagulants as well as for the treatment of large glands [San04, Hai03]. A short learning curve contributes to a high degree of safety for patients. The Holmium laser, although having a similar learning curve for the ablation procedure (HoLAP), carries a steep learning curve and a completely different surgical technique (HoLEP) for glands greater than 40 grams. There is no published evidence, to our knowledge, to suggest that patients on anti-coagulants can safely be treated with Ho:YAG. Published literature cites that the Ho:YAG laser enucleation procedure takes longer than standard transurethral resection and that a learning curve of 50 procedures is needed to be proficient [Sek03]. Patient safety can be compromised during this steep learning curve as evidenced by published literature [Kuo03, Hur02].

3 Mechanisms of Action KTP Non-contact vaporization delivered by a continuous 532nm KTP green laser beam. Delivers uninterrupted heating and rapid vaporization of soft, vascular tissue, making it the tool of choice for the treatment of BPH. The KTP wavelength is highly and selectively absorbed by hemoglobin but experiences virtually no absorption in water (Fig. 1), making KTP the ideal wavelength for soft tissue vaporization under aqueous irrigation and, in particular, for removal of obstructive prostatic tissue. The high absorption in hemoglobin limits penetration of the KTP laser beam to a depth of only 0.8mm (optical penetration depth) [Jac92]. The high power laser beam gets trapped in a very shallow tissue layer that heats up quickly and vaporizes immediately. Vaporization occurs from within the tissue where vapor forms and bursts the collagen matrix [Mal04b]. Fine tissue particles and small vapor bubbles get released from the tissue surface identifying efficient tissue removal. Operation of the KTP laser in a continuous wave mode (continuous stream of light) allows efficient removal of tissue layer-by-layer down to the prostatic capsule. Heat remaining inside the tissue after laser emission has stopped induces a coagulation zone of only a 1-2mm thickness, sufficient to achieve hemostasis and small enough to limit edema formation and avoid gross sloughing of necrotic tissue [Kun97]. Ho:YAG Non-contact ablation delivered by a pulsed 2100nm Ho:YAG laser beam. Interacts mainly with water (Fig. 1). When fired in an aqueous irrigation fluid, each pulse generates a vapor bubble in the irrigant at the end of the laser fiber. Mechanical impact of this vapor bubble causes hard structures to break up, making Ho:YAG an ideal tool for lithotripsy. Early use of HoLAP revealed gland size limitations, due to slow vaporization, leading to the development of the HoLEP technique. Ho:YAG laser is not the ideal tool for vaporization of soft tissue [Gil96,Mal04b,Te04a] because the Ho:YAG laser s poor vaporization efficiency stems from the high absorption of its invisible infrared beam in water (Fig. 1). As a result, the laser fiber must be kept in constant near contact with the tissue to achieve a vaporization effect. Otherwise, the laser energy is largely consumed by formation of the vapor bubble within the irrigant. This makes the ablation procedure, HoLAP, inefficient and laborious to perform. Keeping close tissue contact becomes increasingly difficult as a procedure progresses because of the roughened tissue surface created by initial vaporization. Laser exposure dehydrates superficial tissue layers thus eradicating the target for Ho:YAG laser energy, further reducing vaporization. When energy is delivered in pulses, tissue cools down between pulses making it difficult to reach the vaporization threshold. Images from: "Laser treatment of obstructive BPH: Problems and Progress" Malek RS, Nahen K. Contemp Urol. 2004;16(4):37-43.

4 At-a-Glance Comparison of PVP vs. HoLEP Technique GreenLight PVP Technique for all gland sizes HoLEP Technique for glands 40 grams and larger Step 1: Starting at the Median Lobe, vaporize using a "painting" motion to the level of the transverse fibers of the capsule. Remove tissue from the bladder neck to the verumontanum. i Continue with technique while rotating to lateral lobe. iv. Remove tissue from bladder neck to the verumontanum. v. v Continue with technique rotating 180 degrees for anterior lobes. At the end of procedure, inspect bladder and fossa to ensure hemostasis. Step 1: 5 O Clock Incision and Decision on Median Lobe Enucleation. 5 o clock incision from bladder neck to verumontanum. Similar incision at 7 o clock. i Prepare for enucleation of middle lobe. Step 2: Incision Near Verumontanum Make to define the depth where a plane of enucleation can be identified between adenoma of lateral lobe and surgical capsule. Step 3: Blunt Enucleation To mobilize the lobe off the surgical capsule and away from sphincter. Step 4: Dissection To Bladder Neck Extension of dissection forward allows separation of the lateral lobe from the bladder neck. Step 5: 12 O clock Incision To allow for dissection of both lobes from 12 o clock - 3 o clock between the left lobe and the surgical capsule or 12 o clock - 9 o clock between the right lobe and the surgical capsule. Step 6: Release of Mucosa From Sphincter Identify the band of mucosa holding the lobe inside the sphincter at 1-2 o clock or o clock. Retract the fiber into sheath with energy reduced to 80 Watts from 100 Watts. i Short cuts made to release this band. Step 7: Joining planes from above and below to enucleate the lateral lobe into the bladder. Step 8: Start dissecting the remaining lobe by incision in front of the verumontanum and identifying the plane. Blunt dissection similar to the other side but including the median lobe up to the bladder neck. i Repeat the incision of the band at o clock to enucleate the lobe into the bladder. Step 9: Hemostasis using setting of 1.5 J and 30 Hz (45 Watts) to reduce heat trauma, particularly at the sphincter. Step 10: Morcellation i iv. v. Resectoscope removed and 27 French standard nephroscope sheath and indirect lens used so the morcellator can be inserted. Employment time consistently varies. Morcellation up to 7 grams per minute. Avoid bladder injury * Ensure bladder is full at all times * Use suction to bring tissue closer to prostatic fossa At the end of procedure, inspect bladder and fossa to ensure hemostasis.

5 At-a-Glance Review of KTP vs. Ho:YAG Wavelength Tissue Effect Absorption Properties Technique Treatment time Learning Curve Clinical Proof Catheter Time Retrograde Ejaculation Serious Complications Re-Operation Clinical Education and Support 532 nm - Visible green light GreenLight PVP Excellent for rapid tissue vaporization [Mal04a]. Excellent hemostasis with sweeping motion - 1-2mm of coagulation [Kun97]. Minimal-to-no post-op bleeding [Te04b]. Typically no continuous bladder irrigation in recovery. Most patients are released without a catheter. If a catheter is required, it is usually removed within 24 hours. Almost no absorption in water [Mal04a]. Highly absorbed in oxyhemoglobin - blood in tissue heats up until tissue matrix ruptures resulting in rapid removal of obstructive tissue with excellent hemostasis [Mal04a]. One technique for all gland sizes [Mal04a]. Near contact vaporization technique gives more surgical freedom. Mean lasing time of 39 minutes for mean gland size of 55g, reflecting the high efficiency of the KTP laser [Te04b]. Relatively short. Skills acquired with other cystoscopic procedures largely apply [Mal04]. Clinical proof from peer-reviewed articles documenting excellent clinical outcomes across a wide range of investigators and institutions [Bar04, Hai03, Kun96, Kun97, Mal98, Mal00, Mal04, San04, Te04b]. Durable results to 5 years [Mal03:AUA]. Catheter removal typically within 24 hours except for patients with decompensated bladders or other severe problems (mean 14 hours [Te04b]). 25% [Mal03:AUA] None reported in peer-reviewed published literature. 0% re-operations reported in published data (5-year follow-up) [Mal03:AUA]. Physician training required by manufacturer and available at more than 75 training sites across the U.S. ensures more consistent clinical outcomes [Laserscope Physician Training Policy, p/n ] nm - Invisible infrared light Ho:YAG Excellent for lithotripsy and incision of soft tissue [Mal04a]. Moderate hemostasis with need for catheter post-operatively [Mot99] and some bladder irrigation in recovery room [Gil96]. Highly absorbed in water resulting in loss of energy when tissue contact is not maintained [Mal04a]. Poorly absorbed in oxyhemoglobin - tissue ablation occurs superficially providing precise incision but slow vaporization of obstructive tissue [Gil96]. Two techniques based on gland size. Over 40 grams requires HoLEP which is technically more difficult [Sek03], time consuming compared to TURP [Mat00] and brings the risk of bladder damage from the expensive morcellator [Kuo03]. Learning curve of 50 procedures [Sek03]. Contact vaporization technique - difficult to maintain after initial vaporization, therefore limited to 40 gram glands or smaller [reference internet]. Treating larger glands using HoLAP is documented as inefficient and very time consuming [Gil96]. Long procedure times (TURP: 58 min. vs. HoLEP: 83min [Mat00]). HoLEP has not found wide-spread adoption because of a long learning curve of 50 procedures [Sek03]. Very limited number of peer-reviewed articles available for HoLAP [Gil96, Mot99, Tan03]. Catheter removal varies depending on hemostasis (mean 1.7 days [Mot99]). 96% [Gil99] 1.9% blood transfusions [Kuo03], 9% bladder injuries in early and late cases of study [Hur02], 2% capsule perforations [Kuo03], 8% sexual impotence [Gil99]. 15% re-operation rate (7-year follow-up) [Tan03]. Economic Profile Corporate Support GreenLight and StoneLight 15 watt can be purchased for the same price as a 100 watt Holmium and allow for more flexibility in scheduling and performing two profitable procedures in the same time slot. Faster procedure time due to continuous mode and greater vaporization efficiency with green wavelength. PVP operation time for 55g gland is 39 min.[te04b]. Increased revenue due to ability to operate two lasers simultaneously. Large service and clinical teams to support customers. Strong financial position and 20-year track record ensures stability of laser investment. A single 100 watt holmium limits the OR to just one procedure in a time slot, limiting the profitability and scheduling flexibility needed to accommodate several users every day. Procedure time is longer due to poor/slow vaporization and pulsed delivery system. HoLEP operation time for 54g is 95 min. [Kun04]. Lost BPH revenue when using laser for Stones. Lost Stones revenue when using laser for BPH.

6 fo References [Bar04] Barber J, Muir G. High-power KTP laser prostatectomy: the new challenge to transurethral resection of the prostate, Curr Opin Urol 2004;14: [Gil96] Gilling PJ, Cass CB, Cresswell MD, Malcolm AR, Fraundorfer MR. The use of the holmium laser in the treatment of benign prostatic hyperplasia. J Endourol. 1996;10: [Mal00] Malek RS, Kuntzman RS, Barrett DM. High power potassium-titanyl-phosphate laser vaporization prostatectomy. J Urol. 2000;163: [Mal03:AUA] Malek RS, Kuntzman RS. Photoselective vaporization of the prostate: 5-year experience with high power KTP laser. J Urol. (Suppl) 2003;169:390. [Gil99] Gilling PJ, Mackey M, Cresswell M, Kennett K, Kabalin JN, Fraundorfer MR. Holmium laser versus transurethral resection of the prostate: a randomized prospective trial with 1-year follow-up. J Urol. 1999;162: [Hai03] Hai MA, Malek RS. Photoselective Vaporization of the prostate: Initial experience with a new 80 W KTP laser for the treatment of benign prostatic hyperplasia. J Endourol. 2003;17: [Hur02] Hurle R, Vavassori I, Piccinelli A, Manzetti A, Valenti S, Vismara A. Holmium laser enucleation of the prostate combined with mechanical morcellation in 155 patients with benign prostatic hyperplasia. Urology. 2002;60(3): [Jac92] Jacques SL. Laser-tissue interaction. Photochemical, photothermal, and photomechanical. Surg. Clin N. Am. 1992;72:531. [Kun96] Kuntzman RS, Malek RS, Barrett DM, Bostwick DG. Potassium-titanyl-phosphate laser vaporization of the prostate: a comparative functional and pathologic study in canines. Urology. 1996;48: [Kun97] Kuntzman RS, Malek RS, Barrett DM, Bostwick DG. High-power (60-watt) potassiumtitanyl-phosphate laser vaporization prostatectomy in living canines and in human and canine cadavers. Urology. 1997;49: [Kun04] Kuntz RM, Ahyai, S, Lehrich K, Fayad A. Transurethral Holmium Laser Enucleation of the Prostate vs. Transurethral Electrocautery Resection of the Prostate: A Randomized Prospective Trial in 200 Patients. J Urol. 2004;172: [Kuo03] Kuo RL, Kim SC, Lingeman JE. Holmium laser enucleation of prostate (HoLEP): the Methodist Hospital experience with greater than 75 gram enucleations. J Urol. 2003;170: [Mal98] Malek RS, Barrett DM, Kuntzman RS. High-power potassium-titanyl-phosphate (KTP/532) laser vaporization prostatectomy: 24 hours later. Urology 1998;51: [Mal04a] Malek RS, Nahen K. Laser treatment of obstructive BPH: Problems and progress, Contemp. Urol. 2004; May [Mal04b] Malek RS, Nahen K, Photoselective Vaporization of the Prostate (PVP): KTP laser therapy of obstructive benign prostatic hyperplasia, AUA Update lesson 20, volume 23, 2004, pp [Mat00] Matsuoka K, Lida S, Tomiyasu K, Shimada A, Noda S. Transurethral holmium laser resection of the prostate. J. Urol. 2000;163: [Mot99] Mottet N, Anidjar M, Bourdon O, Louis JF, Teillac P, Costa P, Le Duc A. Randomized comparison of transurethral electroresection and Holmium:YAG laser vaporization for symptomatic benign prostatic hyperplasia. J. Endourol 1999;13: [San04] Sandhu JS, Vanderbrink BA, Egan C, Kaplan SA, Te AE. High-power KTP photoselective prostatectomy for the treatment of benign prostatic hyperplasia in men with large prostates. J Urol. 2004;171:400. [Sek03] Seki N, Mochida O, Kinukawa N, Sagiyama K, Naito S. Holmium laser enucleation for prostatic adenoma: analysis of learning curve over the course of 70 consecutive cases. J Urol 2003;170:1847 [Tan03] Tan AHH, Gilling PJ, Kennet KM, Fletcher H, Fraundorfer MR. Long-term results of highpower holmium laser vaporization (ablation) of the prostate, BJU Int 2003;91: [Te04a] Te AE, The development of laser prostatectomy, BJU Int. 2004;93, [Te04b] Te AE, Malloy TR, Stein BS, et al. Photoselective laser vaporization of the prostate (PVP) for the treatment of benign prostatic hyperplasia (BPH): 12-month Results from the First United States Multi-center Prospective Trial. J Urol. 2004, 172, Part 4; Corporate Headquarters 3070 Orchard Drive San Jose, CA Tel: Tel: Fax: Laserscope France S.A. Parc Technologique 18 rue du Bois Chaland Lisses France Tel: +33/ Fax: +33/ Laserscope UK Ltd Raglan House, Llantarnam Park Cwmbran Gwent NP44 3AX United Kingdom Phone: +44 (0) Fax:+44 (0) Statements in this brochure are based on typical clinical study outcomes and published literature. Laserscope is a registered trademark and GreenLight PV Laser System and GreenLight PVP Procedure are trademarks of Laserscope. Part number Rev A.