Impact of 160 W Greenlight Laser Vaporization of the Prostate on Erectile Function: A Prospective Randomized Controlled Trial with 1-Year Follow-Up

Abstract

Objective: Our aim was to evaluate the impact of 160 W Greenlight laser vaporization of the prostate on erectile function by the International Index of Erectile Function (IIEF-5) in 1-year follow-up in patients with lower urinary tract symptoms (LUTS) caused by benign prostatic hyperplasia (BPH). Background data: Although high-power Greenlight laser has greatly improved the efficiency of vaporization of the prostate, the impact of it on erectile function remains uncertain. Materials and methods: A total of 80 BPH patients with normal erectile function or mild erectile dysfunction (IIEF-5 ≥12) were included in this study. They were randomly assigned to two equal groups: 80 or 160 W. Both groups were compared regarding all relevant preoperative, operative, and postoperative parameters. Urinary function in terms of International Prostate Symptom Score (IPSS), quality of life (QOL) score, maximum flow rate (Qmax), and residual urinary volume (RUV) were evaluated at 1, 3, 6, and 12 months postoperatively. Erectile function was evaluated by IIEF-5 at 3, 6, and 12 months postoperatively. Results: Baseline characteristics of the two groups were comparable. Mean operative time was significantly shorter for the 160 W group. Urinary function in terms of IPSS, QOL, Qmax, and RUV were all significantly improved over baseline in both groups. There were no significant differences in these urinary functional parameters between the two groups at any point of follow-up. IIEF-5 scores of both groups significantly decreased at 3 months postoperatively compared with baseline, but at 6 and 12 months postoperatively, IIEF-5 score of either group increased to baseline, and was not different from baseline. At any point of follow-up, IIEF-5 scores of the two groups were comparable. Conclusions: Greenlight laser (160 W) vaporization of the prostate will not increase the risk of impairing erectile function.

Introduction

Greenlight laser vaporization of the prostate, also named “photoselective vaporization of the prostate (PVP),” is one of the popular surgical methods for the treatment of benign prostatic hyperplasia (BPH). In recent years, high-power Greenlight laser, such as 120 W high-performance system (HPS) and 180 W XPS Greenlight laser (American Medical Systems, MN), was used in clinical settings. Compared with 80 W Greenlight laser, high-power Greenlight laser has greatly improved the efficiency of vaporization of the prostate. However, some potential risks remain unknown, such as its impact on erectile function. In this study, we report the results of a randomized clinical trial performed in our hospital to assess the impact of 160 W Greenlight laser (Realton company, Beijing, China) compared with 80 W Greenlight laser (American Medical Systems, MN) on erectile function in patients with BPH.

Materials and Methods

Participants

Between May 2011 and October 2012, a total of 80 patients with lower urinary tract symptoms (LUTS) caused by BPH were included in this study. Approval for this study was provided by the Institutional Review Board of the Chinese People's Liberation Army (PLA) Navy General Hospital.

The inclusion criteria were having normal erectile function or mild erectile dysfunction (International Index of Erectile Function [IIEF]-5 ≥12), International Prostate Symptom Score (IPSS) >16, maximum flow rate (Qmax) <10 mL/s, residual urinary volume (RUV) <100 mL, failure of previous medical treatment, and ability to give a fully informed consent. Exclusion criteria were having urethral strictures, bladder stones, bladder tumors, neurogenic bladder, prostate cancer, renal dysfunction, urethral surgery history, uncontrolled cardiovascular disease, or diabetes milletus. Patients with an indwelling urinary catheter, or who had been diagnosed with detrusor overactivity or hypocontractility based on urodynamic study were also excluded.

All patients were subjected to the standard urologic preoperative evaluation, including history taking, digital rectal examination (DRE), urine analysis, blood biochemistry analysis, prostate-specific antigen (PSA) test, urodynamic study, prostate volume estimation (by transrectal ultrasonography [TRUS]), RUV and Qmax measurement (by transabdominal ultrasound and uroflowmetry respectively), IPSS, and quality of life (QOL) score assessment. TRUS-guided prostate biopsy was performed in patients with PSA>4 ng/mL, abnormal DRE, and/or suspicious echogenicity on TRUS.

Study design

Sample size was determined after consideration of three factors: (1) In patients with IIEF-5 ≥19, IIEF-5 score decreased from 22.0±2.1 to 19.6±4.5 at 6 months after PVP, based on the study by Bruyère et al.¹ (2) Type 1 statistical error <5%. (3) Type 2 statistical error <10%. Considering the previous factors, a sample size of 40 patients in each group was estimated. This sample size provided a statistical power of 90% and allowed a dropout rate of 10%. Patients were randomly assigned to one of two groups: 80 or 160 W. Randomization was performed using computer-generated simple random tables in a 1:1 ratio.

Patients in the 80 W group received PVP with the 80 W Greenlight laser device (American Medical Systems, MN), whereas patients in the 160 W group received PVP with the 160 W Greenlight laser device (Realton company, Beijing, China). All of the surgical operations were performed by a single surgeon (Cuilong Liu) in a routine manner. In both groups, some intraoperative and early postoperative data were recorded, including operative time, energy consumption, changes in hemoglobin and serum sodium, indwelling catheterization time, postoperative hospital stay, and postoperative volume of the prostate (by TRUS at 1 month postoperatively). Urinary function results in terms of improvement of IPSS, QOL score, Qmax, and RUV were evaluated at 1, 3, 6, and 12 months postoperatively. Erectile function was evaluated by IIEF-5 at 3, 6, and 12 months postoperatively.

Statistical analysis

Statistical analysis was performed using the SPSS 18.0.0 statistical software package (SPSS Inc. Chicago, IL). Qualitative variables are shown by number and percentage. Quantitative variables with normal distribution are shown by their mean,±SD. Quantitative variables with non-normal distribution are shown by their median value (25th,75th centile). Qualitative variables were analyzed by the χ² test or the Fisher exact test. The related samples t test or independent samples t test was used for quantitative variables with normal distribution. The Mann–Whitney U test or Wilcoxon test was used for non-normal variables appropriately. A p value <0.05 was considered significant.

Results

Baseline characteristics

Table 1 provides a summary of the baseline characteristics of both groups. There was no significant difference between the groups regarding any of the studied parameters.

Table 1.

Comparison of Patient Characteristics in Two Groups

	80 W	160 W	p Value
Case	40	40
Age (yr)	62.5±5.1	63.1±4.9	0.593
PSA (ng/mL)	2.6±1.3	2.8±1.5	0.526
Volume of prostate (mL)	86.4±15.5	88.5±15.3	0.544
Qmax (mL/sec)	7.5 (5.9,8.4)	7.5 (6.0,8.5)	0.919
RUV (mL)	50.9±27.0	51.6±25.8	0.896
IPSS	23.9±4.1	23.7±3.9	0.782
QOL	4 (3,5)	4 (3,5)	0.718
IIEF-5	18.2±3.0	18.8±3.0	0.373
Anticoagulation (%)	2 (5.0%)	3 (7.5%)	1.000
Hypertension (%)	16 (40.0%)	15 (37.5%)	0.819
Coronary heart disease (%)	6 (15.0%)	7 (17.5%)	0.762
Diabetic mellitus (%)	4 (10.0%)	3 (7.5%)	1.000

PSA, prostate specific antigen; Qmax, maximum urinary flow rate; RUV, residual urinary volume; IPSS, International Prostate Symptom Score; QOL, quality of life; IIEF-5, International Index of Erectile Function.

Perioperative outcomes

Perioperative outcomes are summarized in Table 2. Although the energy consumption and postoperative volume of prostate were comparable in two groups, the mean operative time was significantly shorter for the 160 W group (p<0.01). There was no significant difference in reduction of hemoglobin and serum sodium level between the two groups. The average time of catheterization and postoperative hospital stay were comparable in the two groups. No major perioperative complications were recorded, and none of the patients required blood transfusion in either group.

Table 2.

Intraoperative and Early Postoperative Outcomes in Two Groups

	80 W	160 W	p Value
Operative time (min)	122.8±42.1	78.5±25.2	<0.01
Energy consumption (kJ)	389.2±60.7	395.1±59.3	0.661
Postoperative volume of prostate (mL)	30.8±6.9	29.1±6.7	0.267
Serum sodium reduction (mmol/ L)	2.0±3.4	1.9±3.2	0.893
Hemoglobin reduction (g/L)	0.7±1.5	0.8±1.7	0.781
Indwelling catheterization time (h)	48.3±17.2	47.5±15.2	0.826
Postoperative hospital stay (days)	4.1±1.2	4.0±1.5	0.761

Follow-up outcomes

Follow-up continued until October 2013, and all of patients completed a 1-year follow-up. Follow-up outcomes are summarized in Table 3. Urinary function in terms of IPSS, QOL, Qmax, and RUV were all significantly improved over baseline in both groups. There were no significant differences in these urinary functional parameters between the two groups at any point of follow-up. In comparison with baseline, IIEF-5 scores of both groups significantly decreased at 3 months postoperatively (p<0.001). But at 6 and 12 months postoperatively, IIEF-5 score of both groups increased to baseline and was not different from baseline. At any point of follow-up, IIEF-5 scores of the two groups were comparable.

Table 3.

Follow-up Outcomes of Urinary Function and Erectile Function in Two Groups

	Baseline	1 month	3 months	6 months	12 months
80 W (n=40)
IPSS	23.9±4.1	12.4±2.8	11.7±2.4	10.9±2.3	11.8±2.6
p ^a		<0.001	<0.001	<0.001	<0.001
QOL	4 (3,5)	3 (2,3)	2 (2,3)	2 (1,2)	2 (1.25,2)
p ^a		<0.001	<0.001	<0.001	<0.001
Qmax(mL/sec)	7.5 (5.9,8.4)	13.7 (10.7,16.2)	14.1 (11.6,16.5)	15.4 (12.8,17.6)	14.1 (11.8,16.2)
p ^a		<0.001	<0.001	<0.001	<0.001
RUV(mL)	50.9±27.0	24.2±14.9	21.2±13.0	18.2±12.1	20.1±12.1
p ^a		<0.001	<0.001	<0.001	<0.001
IIEF-5	18.2±3.0		16.6±2.7	18.4±2.6	18.3±3.0
p ^a			<0.001	0.243	0.645
160 W (n=40)
IPSS	23.7±3.9	13.0±2.3	12.4±2.1	11.5±2.2	12.4±2.0
p ^a		<0.001	<0.001	<0.001	<0.001
QOL	4 (3,5)	3 (2,3)	2 (2,2)	2 (1.25,2)	2 (2,2)
p ^a		<0.001	<0.001	<0.001	<0.001
Qmax(mL/sec)	7.5 (6.0,8.5)	13.0 (10.4,15.3)	13.6 (11.6,16.5)	14.8 (13.5,17.8)	13.8 (12.4,17.0)
p ^a		<0.001	<0.001	<0.001	<0.001
RUV(mL)	51.6±25.8	24.3±13.3	22.2±12.4	20.4±11.7	22.8±12.5
p ^a		<0.001	<0.001	<0.001	<0.001
IIEF-5	18.8±3.0		17.1±2.5	19.1±2.4	18.6±2.6
p ^a			<0.001	0.102	0.210
p ^b
IPSS	0.782	0.339	0.213	0.297	0.299
QOL	0.718	0.786	0.961	0.922	0.601
Qmax	0.919	0.497	0.784	0.939	0.985
RUV	0.896	0.981	0.733	0.406	0.334
IIEF-5	0.373		0.369	0.230	0.606

Comparison with baseline within the same group (related samples t test or Wilcoxon test).

Comparison between 80 W group and 160 W group (independent samples t test or Mann-Whitney U test).

IPSS, International Prostate Symptom Score; QOL, quality of life; Qmax, maximum urinary flow rate; RUV, residual urinary volume; IIEF-5, International Index of Erectile Function.

In addition, we had observed the incidence rate of reverse ejaculation during the follow-up period. It was ∼32.5% (13/40) in the 80 W group and 37.5% (15/40) in the 160 W group. There was no significant difference between two groups (p=0.639).

Discussion

With increasing power of the Greenlight laser, PVP became more and more efficient. But in some aspects, especially for erectile function, the safety of PVP used by high power Greenlight laser remained uncertain. According to our search results, there are only five prospective trials that have analyzed the impact of Greenlight laser vaporization of the prostate on erectile function.

In 2007, Paick et al.² first reported a significant increase in IIEF score after PVP surgery at 6 month follow-up. In 2008, Alivizatos et al.,³ Kavoussi et al.,⁴ and Hamann et al.⁵ all reported no changes in erectile function after PVP at 12 months. But in all of these studies, PVP was performed with 80 W Greenlight laser. Moreover, the baseline levels of erectile function of the subjects in these studies were very low. In other words, there were many patients with erectile dysfunction included in these studies, which would weaken the impact of PVP on normal erectile function. In fact, the study of Kavoussi et al. conducted subgroup analysis of patients with mild or no erectile dysfunction [Sexual Health Inventory for Men (SHIM) ≥17], and demonstrated that there was no statistically significant difference between preoperative and postoperative sexual function after PVP at 12 months in this subgroup, but the sample size of this subgroup was too small (only 13 patients) for statistical analysis to come to a reliable conclusion.

In 2010, Bruyère et al.¹ found that erectile function was maintained after PVP in the overall population, as IIEF-5 scores were comparable pre- and postoperatively. However, they also emphasized that in patients with normal erectile function (IIEF-5>19), postoperative scores were significantly decreased at 6, 12, and 24 months. In this study, 63 patients whose prostate volume was <40 cm³ underwent PVP with 80 W Greenlight laser, and 86 patients whose prostate volume was ≥40 cm³ underwent PVP with 120 W Greenlight laser. They did not find any difference between patients treated with 80 W and patients treated with 120 W, but this comparison was not performed in patients with normal erectile function, but rather in the overall population. Moreover, among the patients with IIEF-5>19 in this study, there were many confounding factors that might have had influence on the results, such as high American Society of Anesthesiology (ASA) scores (23% were ASA 3 or 4), previous surgical treatment for BPH (10.4%), indwelling catheter (79.4%), or ongoing anticoagulant treatment (58.9%). Given these shortcomings of this study, the conclusion that PVP has a potential harmful effect on erectile function in patients with normal erectile function seems to be unreliable.

As far as we know, our study is the first long-term prospective randomized controlled trail on the impact of high power (160 W) Greenlight laser vaporization of the prostate on erectile function among men with potential erectile function. In this study, we established strict inclusion and exclusion criteria in order to minimize the influence of confounding factors on the results. The result shows that the IIEF-5 scores of the 80 W group and the 160 W group both significantly decreased at 3 months postoperatively compared with their preoperative baseline (p<0.001). But at 6 and 12 months postoperatively, IIEF-5 score of both groups increased to baseline and was not different from baseline. Based on this tendency, there is reason to believe that the decrease in IIEF-5 score at 3 months postoperatively might be associated with some short-term reversible negative factors, such as transitory aggravation of urinary irritation symptoms, surgical trauma, and psychological burden. In addition, we found that the IIEF-5 score of each group at 6 months postoperatively was slightly higher than its baseline, although it had no statistical significance. Many previous investigations have shown that erectile dysfunction has a relationship with BPH and lower urinary tract symptoms.^6

–10 Therefore, we think that the later improvement of erectile function might be mainly associated with the gradual elimination of reversible negative factors and the improvement of lower urinary tract symptoms.

The 80 W Greenlight laser, whose wavelength is 532 nm, is created by passing a 1064 nm neodymium-doped yttrium aluminum garnet (Nd:YAG) laser beam through a potassium-titanyl-phosphate (KTP) crystal. In contrast, the even more powerful 160 W Greenlight laser is created by passing a Nd:YAG laser beam through a lithium triborate (LBO) crystal. The 532 nm wavelength is selectively absorbed by hemoglobin. The laser energy can be fully transmitted through irrigation solution into the prostatic tissue, where it is absorbed by hemoglobin. The short optical penetration confines the energy of the 80 W Greenlight laser to a superficial layer of prostatic tissue that is vaporized rapidly with only a 1–2 mm rim of coagulation.¹¹ Several animal studies have been performed with the 120 or 180 W Greenlight laser.^12
–14 These data showed that the depth of coagulation of the 120 or 180 W Greenlight laser is no deeper than 2.5 mm in most cases. As we know, the purpose of PVP is to remove bladder outlet obstruction rather than to remove the largest prostatic adenomas. There is adequate distance between the urethra and the periprostatic structures, such as neurovascular bundles (NVBs), at the end of the PVP procedure. Therefore, PVP is unlikely to result in thermal damage to NVBs. In spite of this, during each operation in our study, we intentionally decreased the operative time and laser power at the prostatic apex as much as possible. In a comparison between the 80 W group and the 160 W group, our study demonstrated that the IIEF-5 scores of the two groups were comparable at any point of follow-up. That is to say that the erectile function might not be impaired because of the increase of laser power, as long as the laser was operating properly.

Conclusions

Erectile function appears to go through a reversible decline and then recover to its baseline after PVP, whether performed with an 80 W or a 160 W Greenlight laser. Compared with 80 W Greenlight laser, 160 W Greenlight laser vaporization of the prostate will not increase the risk of impairing erectile function, whereas it can greatly increase the efficiency of vaporization. Further multicenter large sample prospective studies are needed to confirm our results.

Footnotes

Author Disclosure Statement

No competing financial interests exist.

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