Potassium-Titanyl-Phosphate Laser Photoselective Vaporization for Benign Prostatic Hyperplasia: 5-Year Follow-Up from a District General Hospital

Abstract

Background and Purpose:

The 80-W potassium-titanyl-phosphate (KTP) laser photoselective vaporization of the prostate (PVP) is a minimally invasive surgical option for patients with symptomatic benign prostatic hyperplasia, although evidence of long-term efficacy is limited. We present the long-term outcomes from a heterogeneous patient population.

Patients and Methods:

We prospectively collected data for all patients who underwent 80-W KTP laser PVP treatment between 2004 and 2005. Evaluation occurred pr-operatively, and then at 3, 6, 12, and 60 months postoperatively. This included International Prostate Symptom Score (IPSS), peak urinary flow rate (Qmax), postvoid residual (PVR) volume, serum prostate-specific antigen measurement, and transrectal ultrasonography-estimated prostate volume.

Results:

A total of 115 patients were eligible for analysis, with a mean age of 77 years and mean prostate volume of 55.8 cc. Of these, 74% were operated on for lower urinary tract symptoms, 23% for acute urinary retention, and 3% for chronic retention; 30% of patients were American Society of Anesthesiologists score≥3, and 93% were treated as 23-hour stays. No patients needed blood transfusion, and there were no cases of transurethral resection syndrome. An initial trial-without catheter failed in 11 (9.6%), although 8 of these successfully voided after a further week. At 5-year follow-up, mean Qmax improved from 8.0±5.0 mL to 13.9±7.7 mL and mean IPSS improved from 22±5 to 9±7. There were no cases of urethral strictures, but there was a 3.3% rate of bladder neck stenosis and an overall re-treatment rate of 21% over 5 years.

Conclusion:

We confirm the long-term durability of the 80-W KTP laser PVP with minimal perioperative morbidity. It is therefore a safe option for high-risk patients with medical comorbidities, although its high reoperation rate may limit its use to this specific patient population.

Introduction

B enign prostatic hyperplasia (BPH) is a significant disease of the aging man with evidence of histologic BPH found in almost 75% of men aged 70 to 79.¹ Its effect on quality of life (QoL) is well known, and its financial burden is huge, because 25% to 30% will eventually need treatment.² The range of minimally invasive surgical options for men with lower urinary tract symptoms (LUTS) caused by bladder outflow obstruction secondary to BPH has expanded massively over the past 2 decades. Conventional electrocautery-based transurethral resection of the prostate (TURP), however, remains the gold standard for prostate glands up to 80 g, with open prostatectomy recommended for larger glands (National Institute for Health and Clinical Experience Clinical Guideline 97).

TURP has been shown to have good long-term success rates but has the potential to cause significant morbidity. Contemporary series have reported transfusion rates of 2.9% and transurethral resection (TUR) syndrome rates of 1.4%,³ although the use of bipolar technology has improved the safety profile of TURP and virtually eliminated the risk of TUR syndrome.⁴ Because patients are frequently elderly with numerous comorbidities, and in view of the small but significant complication rates that are associated with TURP, more minimally invasive surgical options have evolved.

The potassium-titanyl-phosphate (KTP) laser was introduced in 2002, and its use has grown exponentially since. The most widely studied KTP laser to date has a maximum power of 80 W, although more recently, the high-performance system using 120 W and the XPS system using 180 W have been developed. Early studies of the 80-W KTP laser were promising, with short-term results comparable to those of conventional TURP, but with a lower rate of perioperative complications.⁵ Longer-term follow-up data have emerged more recently and have confirmed the durable results of the 80-W KTP laser at 5 years, with lower morbidity compared with TURP,^6
–8 Furthermore, a recent randomized controlled trial comparing the 80-W KTP laser with TURP at 1 year follow-up has shown equivalent improvements in subjective and objective parameters, but with significant advantages of the KTP laser in terms of reduced perioperative morbidity.⁹ Consequently, the status of TURP as the gold-standard surgical treatment for these patients is being challenged.

This study provides further long-term results of the 80-W KTP photoselective vaporization of the prostate (PVP) and, to our knowledge, is the first to present long-term data of a heterogeneous population from a single United Kingdom institution.

Patients and Methods

Patient selection

Data were prospectively collected from all patients who underwent KTP laser PVP treatment between November 2004 and October 2005. Preoperative evaluation included history, examination, International Prostate Symptom Score (IPSS) and QoL score, peak urinary flow rate (Qmax), and postvoid residual (PVR) volume. Prostate volume estimated by transrectal ultrasonography (TRUS) was also collected preoperatively. Laboratory studies included a complete blood cell count, serum biochemistry, and prostate-specific antigen (PSA) measurement.

Inclusion criteria

All patients with symptomatic BPH who consented to surgical treatment with the KTP laser were included, as well as patients who presented with acute or chronic urinary retention. Both anticoagulant and antiplatelet medications were discontinued preoperatively.

Exclusion criteria

Those with urethral strictures, neurologic disorders (multiple sclerosis, Parkinson disease, previous spinal surgery, previous stroke), prostatic malignancy, or a history of prostatic surgery were excluded from the study.

Operative technique

All PVP were performed with the 80-W GreenLight system (American Medical Systems, Minnetonka, MN) using the standard technique described by Malek and associates.¹⁰ The procedures were performed by three different surgeons, with a combined experience of 38 procedures. All surgeons had completed the KTP laser master class, underwent a preceptorship period, and were mentored appropriately. Perioperative antibiotic prophylaxis was administered, and general or spinal anesthesia was used. Near-contact KTP laser vaporization was performed with a 600-μm side-firing fiber with a quartz capsule over the 70-degree lateral deflecting fiber end. The laser fiber was introduced through the working channel of a 22.5F continuous flow laser cystoscope, and saline was used as an irrigant. Laser time was recorded for each procedure.

Postoperative evaluation

After surgery, patients were discharged and given an appointment for a trial without catheter (TWOC) in the next available “TWOC clinic,” usually within 1 to 5 days. Patients were instructed to return for reevaluation immediately if they had any concerns; otherwise, they were seen in a dedicated nurse-led KTP laser follow-up clinic at 3, 6, and 12 months. Thereafter, they were contacted to attend the dedicated follow-up clinic at the fifth postoperative year, while those who were unable to attend were asked to complete an evaluation and IPSS questionnaire via telephone. Evaluation consisted of history, IPSS and QoL score, Qmax, PVR, and PSA measurement.

Data were analyzed using Microsoft Excel 2007 and integrated statistical functions. The two-tailed Student t test was used for statistical validation, with P values<0.01 considered to be statistically significant.

Results

A total of 131 men underwent a laser PVP procedure during the period analyzed. By the 5-year follow-up period, 16 patients had died from unrelated causes and were therefore excluded from the study, leaving 115 who were eligible for analysis. Twenty-five patients were lost to follow-up, and therefore a total of 90 patients were contactable at 5 years. Of these, 56 were able to attend the outpatient clinic for flow-rate and PVR measurement, while another 10 who were unable to attend completed the IPSS questionnaire via telephone.

Baseline patient characteristics and perioperative data are shown in Table 1. Patients had a mean age of 77 with a mean prostate volume of 55.8 cc. Seventy-four percent were operated on for LUTS, 23% for acute urinary retention, and 3% for chronic retention. Laser time ranged from 8 to 93 minutes (mean 42±15 min), during which 51 to 250 kJ (mean 113±47 kJ) of laser energy was delivered. The American Society of Anesthesiologists (ASA) grade of patients ranged from 1 to 3, and 30% of patients were ASA≥3. All but six patients were treated as 23-hour stays. Those who stayed longer had either postanesthesia sequelae or social factors preventing early discharge. In the immediate postoperative period, none of the patients needed blood transfusion. Urinary retention developed in 11 patients, however, postcatheter removal, and thus they needed recatheterization. Eight of these voided successfully after a further week, whereas 3 (of the 90 contactable for 5-year follow-up) needed long-term catheterization or clean intermittent self-catheterization (CISC) for high-residual volumes.

Table 1.

Baseline Characteristics

	Mean±SD
Patient age	77.6±7.6 n=115 (100%)
IPSS	22±5 n=84 (73%)
Peak flow (mL/sec)	8.0±5.0 n=88 (77%)
Postvoid residual volume (mL)	321±394 n=88 (77%)
Prostate volume (cc)	55.8±29.3 n=83 (72%)
PSA (ng/mL)	4.2±4.8 n=80 (70%)

n=number of patients for whom data were available preoperatively.

IPSS=International Prostate Symptom Score; PSA=prostate-specific antigen.

Outcomes

After surgery, the mean serum PSA value decreased from baseline by 38%, although 25 patients had a PSA rise after surgery. Of these, 22 patients underwent a prostate biopsy, with one positive diagnosis of adenocarcinoma and one case of prostatitis. The remaining three did not have a biopsy because of recent negative biopsy results. All patients underwent PSA monitoring at least yearly over the follow-up period, with two further cases of adenocarcinoma found. After excluding patients with adenocarcinoma of the prostate and those who needed TURP for recurrent tissue, the mean PSA value at 5 years was 3.4 (standard deviation [SD] 2.8) ng/mL.

Qmax showed a significant improvement at 5 years postoperatively. There was a 229% improvement in mean flow rate after 1 year, and at 5 years, the improvement in mean flow rate compared to that preoperatively was maintained at 74.2%.

Symptomatic outcomes revealed a 77% improvement in the IPSS score at 6 months postoperatively. By 5 years, the improvement remained at 58.4% compared with preoperatively (Table 2).

Table 2.

Maximum Urinary Flow Rate, International Prostate Symptom Score, and Prostate-Specific Antigen Outcomes

	Baseline	3/12	6/12	12/12	5 years	Mean % improvement (baseline to 5 years)
Total number (%)	115 (100)	54 (47)	35 (30)	23 (20)	56 (62)	–
Mean PVR±SD (mL)	321±394 n=88	61±67 n=54	72±89 n=35	66±71 n=23	76±60^a n=56	76.5±84.9
Mean Qmax±SD (mL/sec)	8.0±5.0 n=88	20.4±8.5 n=54	20.5±10.3 n=35	26.4±12.9 n=23	13.9±7.7^a n=56	74.2±53.6
Mean IPSS score±SD	22±5 n=84	10±5 n=54	5±2 n=35	–	9±7^a n=66	58.4±29.6
Mean PSA±SD (ng/mL)	4.2±4.8 n=80	2.6±2.2 n=54	2.6±1.8 n=35	3.5±3.5 n=23	3.4±2.8 n=41	18.7±17.3

P<0.01.

n=total number of patients for whom data were available.

PVR=postvoid residual; SD=standard deviation; Qmax=maximum urinary flow rate; IPSS=International Prostate Symptom Score; PSA=prostate-specific antigen.

Complications

Adverse events included transient dysuria in three patients, urinary tract infections in five patients, incontinence of urine in one patient, and erectile dysfunction in one patient. There was one case of ureteral injury that necessitated a percutaneous nephrostomy and antegrade stent insertion with no further long-term problems.

No patients had hematuria necessitating transfusion. Twenty-eight patients received anticoagulation medication (warfarin), but this had been discontinued 3 days before the procedure.

Of the 90 contactable patients, 19 (21%) needed further surgery over the 5-year follow-up period, with 3 (3.3%) needing long-term catheterization or CISC. Of those who needed further procedures, 16 (17.7%) had recurrent adenoma (14 underwent bipolar TURP and 2 had redo laser PVP). Three (3.3%) had a bladder neck incision, and there were no cases of urethral strictures. Interestingly, bladder stones developed in five patients postoperatively necessitating cystolitholopaxy during their TURP.

Discussion

The KTP laser is a 532-nm wavelength laser, created by passing the 1064-nm neodymium: yttrium-aluminium-garnet (Nd:YAG) laser energy through a KTP crystal. The resulting “green-light” laser has a tissue penetration depth of only 1 to 2 mm with a high absorption affinity for oxyhemoglobin and a low absorption affinity for the aqueous irrigant fluid. These unique properties allow effective prostatic tissue vaporization with only a thin rim of coagulation and minimal blood loss. The “quasicontinuous” pulse frequency also reduces charring, and coagulative necrosis of prostatic tissue is reduced if the energy is delivered from a distance of less than 5 mm.

To determine the benefit of this technology, it should be compared with the current gold standard, monopolar TURP. A recent meta-analysis showed good long-term outcomes for monopolar TURP, with a 162% improvement in Qmax and 70% reduction in IPSS over 5 years.¹¹ Contemporary data have also shown long-term reoperation rates of 2% (for recurrent adenoma) and 5.8% (for bladder neck stenosis).¹²

Studies over the past several years have shown that the 80-W KTP laser has comparable short-term clinical outcomes to those of monopolar TURP,⁹ but with reduced perioperative complications and shorter catheterization times and length of hospital stay. The procedure has been successfully used in large glands,¹³ high-risk patients,¹⁴ and even those receiving oral anticoagulants¹⁵ (although in our institution, we still discontinue anticoagulants preoperatively), without significant complication.

Early studies with small numbers of patients and short-term follow-up showed significant improvements in symptom score, flow rate, and PVR volume.⁵ After this, a larger multicenter study by Te and colleagues¹⁶ that involved 139 men showed mean improvements in the American Urological Association Symptom Index (AUA SI), QoL, PVR, and Qmax of 83%, 79%, 71%, and 165%, respectively. Importantly, these results were durable at midterm (3-year) follow-up. Re-treatment rate in this series was 4.3%.

It is clear that the long-term benefit of any surgical procedure should be well studied before any recommendations regarding its widespread use. Because this technology has been continually evolving over the past decade, however, from the early 40-W and 60-W systems to the latest 80-W, 120-W and now 180-W lasers, long-term outcome data have been slow to arrive.

In one single-center study of 500 patients, including 45% who were receiving oral anticoagulants, there were significant improvements in IPSS, QoL, Qmax, and PVR that were sustained at 5-year follow up.⁶ In this study, 5.2% of procedures had to be converted to TURP for various reasons and the postoperative transfusion rate was 0.4%. Bladder neck and urethral strictures occurred in 3.6% and 4.4%, respectively, after 5 years, and the overall re-treatment rate was 14.8% (6.8% for recurrent adenoma). This higher stricture rate was attributed to the larger-sized laser cystoscope (26F) used initially, which was subsequently changed to the smaller 22.5F scope. Only 27 of the initial 500 patients were available at 5-year follow-up, however.

Another single-center retrospective study of 246 patients confirmed the durability of the 80-W KTP laser PVP at 5-year follow-up, with improvements in AUA SI, Qmax, and PVR of 78.7%, 171.8%, and 77.1%, respectively.⁷ The overall re-treatment rate was 8.9% after 5 years, with a 1.2% development of bladder neck contractures. In the earliest study with 5-year follow-up, Malek and coworkers⁸ demonstrated significant improvements in mean Qmax of 170% at 5 years, although this study used the 60-W laser. The rate of bladder neck contractures was also low at 2%.

Our data provide further long-term outcomes of the 80-W KTP laser PVP at 5-year follow-up from three different surgeons at a single institution. We found an initial improvement in mean Qmax at 3 months (155%), which was maintained at 1-year follow-up. By 5 years, the improvement in Qmax had reduced but was still a 74.2% improvement compared with baseline. The improvement in mean IPSS and PVR at 5 years was 58.4% and 76.5%, respectively. Importantly, we had no cases of urethral strictures over the 5-year period, which may be related to the smaller-diameter laser cystoscope used (22.5F). Furthermore, significant hematuria necessitating a blood transfusion did not develop in any patient perioperatively, and 93% of patients were discharged within 23 hours.

This low perioperative transfusion rate compares favorably with that of monopolar TURP. A recent randomized study into the treatment of large prostate glands (>70 mL) showed an 8.1% transfusion rate for monopolar TURP (compared with 0% with 80-W KTP laser PVP),¹⁷ and Al-Ansari found similarly nonexistent transfusion rates with the 120-W laser.¹⁸ In comparison with open prostatectomy, the rate of bleeding necessitating transfusion is also lower for KTP laser PVP.¹⁹

Transient dysuria was noted in only three patients in our study, which is lower than other published rates. This could be because all patients were specifically made aware of this symptom, and its temporary nature, during the consent process and so may not have necessarily reported it postoperatively. Furthermore, patients were not seen in the clinic until 3 months postprocedure, and it is therefore possible that they may have forgotten about the dysuria, even if they had experienced it.

We report a very low rate of other perioperative complications (eg, urinary tract infections), comparable to those of the other long-term studies mentioned above.

We have identified some important long-term complications of the 80-W KTP laser, however. We observed an overall reoperation rate of 21% over the 5-year period (17.7% for recurrent adenoma), which is greater than that published in the literature. In the only published long-term studies of the 80-W KTP laser, Ruszat and associates⁶ and Hai⁷ reported overall reoperation rates at 5 years of 14.8% (6.8% for recurrent adenoma) and 8.9% (7.7% from recurrent adenoma), respectively. The first of these studies, however, suffered from a high attrition rate with data for only 27 of the original 500 available at 5 years.

In their prospective study of KTP PVP for large prostates, Horasanli and coworkers¹⁷ reported a reoperation rate for recurrent tissue of 17.9% after only 6 months (similar to our results), compared with 0% for TURP, as well as a 5.1% reoperation rate for urethral strictures. Furthermore, in an update of their long-term data, Rieken and colleagues²⁰ found a very high overall reoperation rate of 50% (34.2% for recurrent adenoma) after a mean follow-up of 56.8 months. The mean prostate volume in this study was similar to that in ours, at 57.4 mL. Therefore, although we report a higher overall reoperation rate than the currently published long-term reports, this may be related to the fact that these studies are from high-volume surgeons experienced in KTP laser PVP, whereas our data are derived from three different surgeons near the beginning of their experience with this laser. Thus, our data are likely to be more representative of the true “real-world” situation, rather than that seen in high-volume centers. With the advent of higher-powered lasers, these rates may improve further.

On further analysis, we discovered that four of those who underwent bipolar TURP reoperations had less than 2 g of tissue resected, mainly at the prostatic apex. This is likely because we were more conservative in our vaporization of the apical tissue near the beginning of our experience with the laser for fear of causing incontinence. The mean (SD) resection weight of the other reoperations was 29.1 (±4.2) g.

Interestingly, we found that bladder stones developed postoperatively in five patients. This finding has only been reported rarely in the literature.²¹ A large amount of coagulation necrosis, which occurs if near-contact vaporization is not performed, may lead to the process of dystrophic calcification—calcification occurring in necrotic tissue, commonly as a reaction to tissue damage. It has been demonstrated that the KTP laser induces a wider zone of coagulation necrosis compared with TURP,²² and it has been suggested that necrosis creates an environment lacking in calcification inhibitors.²³ Furthermore, long-term exposure of this necrotic tissue to infected, alkaline urine may exacerbate the risk of stone formation.

The advantage of the newer high-power KTP lasers is the maintenance of vaporization efficiency at distances of up to 3 to 5 mm from the target tissue, thereby minimizing the amount of coagulation necrosis that occurs. We would therefore expect a lower rate of stone formation with the use of these lasers, although whether this is truly the case remains to be seen.

Together, these results represent an advantage over traditional TURP in terms of perioperative safety. The higher long-term re-treatment rates are concerning, however. We believe that these data are a more accurate reflection of the real-life long-term outcomes from a district general hospital in a heterogeneous patient population, rather than previous results that have been published from high-volume centers. The low perioperative morbidity may justify the use of this laser for high-risk patients, although they should be counseled regarding the long-term reoperation rate.

Enucleating techniques, such as holmium laser enucleation of the prostate (HoLEP), represent another alternative to traditional monopolar TURP and are the endoscopic equivalent of an open prostatectomy. A meta-analysis of randomized controlled trials has confirmed the low perioperative complication rates of HoLEP (comparable to those of KTP laser PVP), and long-term durability has been proven at more than 5 years.²⁴ These long-term studies have also shown a long-term re-treatment rate comparable to that of TURP, of 1.4% to 4.3%,^25,26 and lower than the rates seen for KTP PVP.

The uptake of this technology, however, has been limited by its perceived steep learning curve compared with KTP laser PVP. A recent study reported that an endourologist inexperienced with HoLEP could obtain outcomes similar to experienced surgeons after 50 cases.²⁷ With respect to KTP laser PVP, it has been shown in one study that there is no change in symptomatic outcomes, adverse events, or blood loss with increasing experience,²⁸ although it has been suggested that 30 to 50 cases are needed to achieve sufficient competence.²⁹

More recently, a number of short-term prospective trials have emerged comparing KTP laser PVP with the current gold standard, monopolar TURP. These trials have confirmed the superiority of laser PVP over TURP in terms of blood loss, time to catheter removal, and length of hospital stay. A prospective nonrandomized study with 2-year follow-up revealed significantly lower rates of intraoperative bleeding (3% vs 11%), blood transfusions (0% vs 5.5%), capsule perforations (0.4% vs 6.3%), and early postoperative clot retention (0.4% vs 3.9%).³⁰ In this study, there was no significant difference in IPSS and PVR, although the improvement in Qmax was greater with TURP. Furthermore, the re-treatment rate was higher with laser PVP (6.7% vs 3.9%), although this was not statistically significant.

A more recent study with short (1 year) follow-up reported on 120 patients randomized to 80-W KTP laser PVP or TURP. At 12 months, improvements in IPSS and Qmax were similar, with significantly improved length of hospital stay, catheterization time, and adverse events for the laser PVP group. Costs were also 22% less ($3221 vs $4277 for TURP), primarily because of reduced length of hospital stay.⁹ Unfortunately, there are no direct head-to head comparisons of KTP laser PVP with HoLEP.

We acknowledge the limitations of this study. It is a nonrandomized, single-center study, and although data were collected prospectively, we did not have accurate data for certain important variables (such as mean catheterization times and postoperative TRUS-determined prostate volumes). Furthermore, a significant number of patients were lost to follow-up over the 5-year study period, thus affecting the reliability of the results obtained. Ideally, a randomized trial comparing KTP laser PVP with TURP or holmium laser enucleation would have more clearly assessed the differences in long-term outcomes. Furthermore, the data presented are from the time of our initial experience with the KTP laser. Over the past several years, our experience has improved, and anecdotally we have found our reoperation rates have fallen.

We have described the long-term outcomes from three different surgeons, which increases the generalizability of the results and highlights the consistency of outcomes of the KTP laser in many hands. We provide further long-term data of the 80-W KTP laser, which will prove useful considering the lack of long-term literature that is currently available.

The development of other minimally invasive options, such as holmium laser enucleation, thullium laser enucleation, and bipolar TURP, as well as higher-powered KTP lasers (eg, 180 W), may offer similar outcomes to TURP with reduced reoperation rates, although future prospective trials will determine whether this is truly the case. This study, however, adds weight to the argument that laser PVP technology has sustainable long-term outcomes with minimal postoperative morbidity.

Conclusion

Laser PVP technology has expanded massively over the past decade and continues to evolve. More and more prospective randomized studies are being published confirming the comparable initial results of the KTP laser PVP to those of TURP over the short term. We have provided further evidence that the outcomes are sustainable over a 5-year follow-up period with minimal complication rates, short hospital stays, and minimal blood loss. Further prospective, randomized, long-term studies comparing KTP laser PVP with TURP are needed, however, to accurately determine its durability. In any case, the low reported rate of perioperative complications may justify its use in high-risk patients, despite the high long-term reoperation rate.

Footnotes

Acknowledgments

We are thankful to the urology specialist nurses—Wendy Muir, Carol Davidson, and Ann Chambers—for their assistance in collecting the data.

Disclosure Statement

No competing financial interests exist.

Abbreviations Used

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