Retrospective Analysis of Short-Term Outcomes After Monopolar Versus Laser Endoscopic Enucleation of the Prostate: A Single Center Experience

Abstract

Introduction:

Endoscopic enucleation of the prostate (EEP) has been recognized as a viable treatment modality for men with benign prostatic hyperplasia (BPH). The aim of our study was to compare the efficacy and functional outcomes of three different techniques of EEP, including monopolar enucleation (MEP), holmium laser enucleation of the prostate (HoLEP), and thulium laser enucleation of the prostate (ThuLEP).

Methods:

The study consisted of a retrospective comparison of pre- and postoperative parameters in men undergoing three types of EEP: MEP, HoLEP, and ThuLEP. Functional parameters were evaluated before and 6 months after surgery, which included the International Prostate Symptom Score, maximum flow rate, postvoid residual volume, prostate volume, and sodium levels of all patients.

Results:

A total of 551 men with the mean age of 67.1 years were included in the study. Of these, MEP was performed on 95 patients, HoLEP was performed on 254 patients, and ThuLEP on 202 patients. The mean mass of morcellated tissue obtained during the three techniques did not differ significantly (p > 0.05). Mean procedure times of ThuLEP and HoLEP were shorter than MEP demonstrating 72, 76, and 86 minutes, respectively (p < 0.01). The mean catheterization time following laser EEPs was shorter than MEP as shown by 1.3, 1.3, and 3.8 days, respectively (p < 0.01). Hospital stay times of HoLEP and ThuLEP were shorter than MEP demonstrated by 3.3, 3.4, and 6.9 days, respectively (p < 0.01). Patients after MEP had significant decrease in postoperative hemoglobin and sodium levels. All the groups showed statistically significant improvement in the aforementioned parameters following treatment.

Conclusions:

Both techniques of laser enucleation proved to be efficacious in the management of BPH. MEP of the prostate seems to be a highly promising addition to the list of enucleation techniques and was determined to be an effective and acceptable procedure, despite a higher complication rate.

Introduction

Endoscopic enucleation of the prostate (EEP) has been recognized as a viable treatment option for men with lower urinary tract symptoms due to benign prostatic hyperplasia (BPH), up to 80 cc.¹ The first modality of EEP was monopolar enucleation (MEP), which was first described by Hiraoka and colleagues, who pioneered the technique in 1986.² However, the method of MEP did not gain much popularity at the time, largely due to a steep learning curve and outcomes being comparable to those of transurethral resection of the prostate (TURP).^2,3

EEP can be performed by means of several sources of energy, the most well recognized of which being holmium laser enucleation of the prostate (HoLEP). This operation modality has experienced wide acceptance globally and has been confirmed as an efficacious procedure by several extensive meta-analyses.^4

–9 Development of novel technologies resulted in the emergence of additional laser energy sources, such as the thulium laser that are commonly used in surgical procedures today. In 2008, the thulium laser was first introduced as a viable resection method for the treatment of BPH in a head-to-head comparison with TURP.¹⁰ When the technology began to become more readily available, the procedure was further refined by Bach and colleagues in 2009 by using the thulium:YAG laser for vapoenucleation of the prostate.¹¹ Subsequently, the thulium laser was fully integrated into endoscopic enucleation surgeries, resulting in the procedure known as thulium laser enucleation of the prostate (ThuLEP).¹²

The ever-growing popularity of laser EEP has rekindled interest in MEP among many practicing urologists. Many authors point out with increasing frequency that EEP efficacy is less dependent on the energy source, and hinges more on the technique itself and surgeon's skills.^13,14 This makes MEP relevant as ever for it may be practiced in centers devoid of laser equipment and used in patients who have contraindications for monopolar TURP (prostate volume >80 cc).

Therefore, comparing the efficacy of MEP and EEP is of utmost importance. To our best knowledge, the postoperative outcomes of MEP and laser enucleation of the prostate have not been previously compared. The goal of this study was to compare perioperative efficacy, functional outcomes, and the safety profile of MEP, HoLEP, and ThuLEP. Although these three procedures are no longer necessarily novel in some parts of the world, the analysis presented in this study will be one of the first comparing the efficacy of ThuLEP and MEP against the most widely recognized enucleation procedure, HoLEP.

Methods

After obtaining approval from the Institutional Review Board Committee of Sechenov University, we queried our database to retrieve the medical and surgical information of all men who underwent surgical treatment for BPH by means of MEP, HoLEP, and ThuLEP between 2014 and 2016. In general, surgical intervention was offered for those with urinary retention and indwelling urethral catheters or those with poor quality of life (QoL; International Prostate Symptom Score [IPSS] >20) despite maximal medical therapy. Those with history of prior prostate surgery, urethral strictures, or bladder stones were excluded. Fifteen patients received antiplatelet therapy (aspirin), which was stopped 5 days before surgery. In all patients, serum hemoglobin and sodium were measured 1 day before the surgery and on the next day after surgery.

Patients were randomly assigned to different surgical groups. All procedures were performed by a single surgeon (D.E.) who began learning the three techniques simultaneously at the start of the study (2014).

Preoperative assessment included physical examination, prostate-specific antigen assay, and digital rectal examination. Functional measures, including the IPSS, maximum flow rate (Q_max), and postvoid residual volume (PVR) were recorded before surgery, as well as 3 and 6 months thereafter. Prostate volume was measured on transrectal ultrasonography by a radiologist before and 6 months after surgery. Stress incontinence was assessed with a simple yes/no questionnaire. The patients were required to answer whether urine leaks developed during coughing or sneezing (Grade I), during rapid movement (Grade II), or in recumbent position (Grade III).

Surgical techniques

All surgeries were performed using a No. 26F resectoscope as described by the European Association of Urology (EAU's) classification of BPH management.¹ MEP was performed with a monopolar generator, hook electrode, and straight loops (using 1.5% glycine irrigation). At the first step of the procedure, a deep incision at the 5 o'clock position from the bladder neck to adenoma apex was made with the hook electrode. At the second step, we perform enucleation of the median lobe (if it is presented) performing incision at the 7 o'clock position. Incisions were as deep as the circular fibers of the prostate capsule and were connected proximally at the verumontanum for the median lobe to be enucleated step-by-step into the bladder. Next, the hook electrode was used for circular exposure of the adenomatous lobes at the 5 o'clock position. The resectoscope was introduced counterclockwise at the 2 o'clock position. An incision was then made at the 12 o'clock position and extended to the level of the verumontanum. The incisions at the 12 and 2 o'clock positions were connected; then the left lobe was enucleated into the bladder.

The right lobe of the gland was enucleated in a similar manner: the initial incision at 7 o'clock was made clockwise, followed by an 11 o'clock cut, which extended along the capsule to join with the initial incision, thus exposing the right lobe.

Note that both lobes were not completely liberated from the prostate capsule with the hook electrode. Instead, the lobes were disconnected using the standard loop, which allowed for the avoidance of any bladder neck injury. At the final step, the resected tissue was extracted from the bladder using a morcellator. The operation was concluded with coagulation of bleeding vessels with the standard loop.

For HoLEP, we used the VersaPulse System (Lumenis, Israel) utilizing the 550 μm laser fiber. The energy was set at 70 W and decreased to 40 W when incising distally at the seminal crest area. For ThuLEP, we used the Urolase system (NTO IRE-POLUS, Russian Federation) and a 600 μm fiber. The thulium laser was set with a mean output power of 60 W and energy of 1.5 J; power was decreased to 30 W when incising distally at the seminal crest area. Tissue morcellation was completed with the VersaCut Morcellator (Lumenis, Israel). For both laser EEPs we used 0.9% normal saline irrigation.

Laser enucleation of the prostate (holmium and thulium) was performed using the three-lobe, two-lobe, or en-bloc techniques. In the three-lobe technique, bladder neck incisions at 5 and 7 o'clock were created. If the median lobe was not present, the two-lobe technique was performed with first incision at the 6 o'clock position. Incision depth was limited to the circular fibers of the prostate capsule. The incisions were connected proximally at the verumontanum for the median lobe to be enucleated into the bladder. The left lobe was enucleated first, starting at the 5 o'clock position. The endoscope was then introduced counterclockwise at the 2 o'clock position. Next, an incision was made at 12 o'clock and extended to the level of the verumontanum. The incisions at the 12 and 2 o'clock positions were connected, and the left lobe was enucleated into the bladder. The right lobe of the gland was enucleated in a similar manner: the initial incision at 7 o'clock was made clockwise, an 11 o'clock incision was then extended along the capsule to join with the previous cut, thus exposing the right lobe. The final step was morcellation of hyperplastic nodes.¹⁵

Postoperative assessment and grading complications

At the end of the procedure, irrespective of energy source, a 22F three-way Foley catheter was placed to facilitate adequate drainage. The catheter was subsequently removed on the first or second postoperative day unless prolonged catheterization was required due to persistent hematuria. All patients received perioperative antibiotics, and for those with indwelling catheters or evidence of urinary tract infection, a 10-day postoperative regimen was generally advocated. Postoperative complications were assessed using the Clavien–Dindo classification.¹⁶ To determine QoL after 6 months following surgery, an IPSS-QoL questionnaire was used with a grade scale from 0 (delighted) to 6 (terrible).

Statistical analyses

Baseline characteristics, perioperative data, and descriptive statistics from the procedures were collected. Continuous variables were compared by one-way analysis of variance test. Categorical variables were compared through Chi-square tests. Nonparametric variables were compared with Kolmogorov–Smirnov and Kruskal–Wallis tests. Post hoc analysis was performed with Mann–Whitney U test. All statistical analyses were carried out using SPSS Statistics 22.0 (SPSS, Inc., Chicago, IL). A p-value <0.05 was considered to indicate statistical significance.

Results

A total of 551 men with the mean age of 67.1 (range 54–87) years were included in the study. Of these, HoLEP was performed on 254 patients, MEP on 95 patients, and ThuLEP on 202 patients. All interventions were carried out by one surgeon (D.E.). There was no difference observed among the three groups with regard to demographics, prostate volume, preoperative Q_max, or IPSS (Table 1). Noteworthy, those treated with laser enucleation (HoLEP and ThuLEP) were more likely to be treated with antiplatelet therapy at the time of surgery (p = 0.02).

Table 1.

Preoperative Parameters for All Three Cohorts of Patients Who Underwent Treatment for Prostate Cancer

	Age (years)	Prostate volume (cc)	IPSS (score)	QoL (score)	Q_max (cc/s)	Voiding volume (cc)	PVR (cc)	PSA (ng/cc)	Preoperatve sodium (mmol/L)	Preoperatve hemoglobin (g/dL)	Antiplatlet therapy
HoLEP	66.5 (±7.7)	89.7 (±43.3)	21.9 (±1.1)	4.1 (±0.8)	7.5 (±1.7)	184.4 (±42.4)	72.4 (±28.6)	4.5 (±2.6)	139.6 (±6.8)	13.6 (±1.0)	10
MEP	68.0 (±6.7)	85.6 (±36.0)	21.5 (±1.3)	4.0 (±0.8)	7.9 (±1.8)	187.8 (±45.2)	69.5 (±25.4)	3.9 (±2.2)	138.9 (±7.2)	13.5 (±1.1)	0
ThuLEP	67.1 (±7.2)	91.0 (±32.1)	21.8 (±1.6)	4.0 (±0.8)	7.6 (±1.9)	185.0 (±44.0)	70.1 (±28.7)	4.5 (±3.1)	140.0 (±7.3)	13.5 (±0.9)	5
P	0.268	0.516	0.198	0.471	0.151	0.738	0.621	0.149	0.539	0.382	0.028

HoLEP = holmium laser enucleation of the prostate; IPSS = International Prostate Symptom Score; MEP = monopolar enucleation; PSA = prostate-specific antigen; PVR = postvoid residual volume; Q_max = maximum flow rate; QoL = quality of life; ThuLEP = thulium laser enucleation of the prostate.

Mean operative time for laser enucleation was shorter compared with MEP (Table 2). The mean mass of morcellated tissue did not differ significantly among the three groups. The mean catheterization time following laser interventions was shorter compared with monopolar resection as were the hospital stay times (p < 0.01 for each). In the MEP group, catheterization time was 2 to 3 days on average, which was due to higher frequency of retention (only during first procedures) than in laser EEPs. Patients after MEP had significant decrease in postoperative hemoglobin and sodium levels compared with laser enucleation techniques (Table 2).

Table 2.

Intra- and Postoperative Parameters in All Three Cohorts of Patients

	HoLEP (n = 254)	MEP (n = 95)	ThuLEP (n = 202)	p
Mean surgery time (minutes)	75.9 (±35.3)	85.9 (±39.1)	71.6 (±31.3)	<0.01^*
Enucleation time (minutes)	50.1 (±22.0)	59.9 (±27.4)	49.0 (±18.4)	<0.01^*
Morcellation time (minutes)	24.5 (±13.1)	26.5 (±14.8)	26.6 (±11.5)	0.28
Mean mass of extracted tissue (g)	74.2 (±35.9)	70.1 (±28.6)	75.6 (±26.6)	0.35
Catheterization time (days)	1.3 (±0.6)	3.8 (±1.7)	1.3 (±0.5)	<0.01^*
Hospital stay (days)	3.3 (±0.6)	6.9 (±1.8)	3.4 (±0.6)	<0.01^*
Postoperative hemoglobin (g/dL)	12.1 (±1.3)	11.4 (±1.5)	12.0 (±1.0)	0.382
Hemoglobin decrease (g/dL)	1.6 (±0.8)	3.2 (±1.0)	1.6 (±0.3)	<0.01^*
Postoperative sodium (mmol/L)	138.2 (±7.0)	134.9 (±6.4)	138.7 (±7.3)	<0.01^*
Sodium decrease (mmol/L)	1.4 (±1.2)	3.9 (±1.7)	1.1 (±1.1)	<0.01^*

No difference between ThuLEP and HoLEP groups (p > 0.05).

Ureteral orifices were damaged in 2 (0.8%) patients after HoLEP and 1 (0.5%) patient after ThuLEP. No ureteral orifice damage was noted in the MEP group (p = 0.41). All three patients were closely monitored after surgery to assess the upper urinary tract. One HoLEP patient with damaged ureteral orifices underwent intraoperative upper urinary tract stenting. In the second case, we decided to refrain from draining of the upper urinary tract intraoperatively. This patient showed no signs of dilation of the renal collecting system during 1 month of follow-up. In the ThuLEP patient, the surgeon also refrained from intraoperative stenting. On the second day of follow-up, the patient had dilation of the pelvicaliceal system (pelvis–up to 1.5 cm; calix–up to 0.5) with no symptoms. At 14 days after surgery, the dilation persisted, yet still no signs of affected urinary outflow were present. At 1 month of follow-up, no dilation of the collecting system was detected.

Six months after surgery, we evaluated IPSS, Q_max, QoL, and PVR. All the groups showed statistically significant improvement after surgery (Table 3). After MEP, there was one patient (1.1%) who experienced TURP syndrome. Operation was stopped and 20 mg furosemide with hypertonic sodium chloride was introduced. After surgery, the patient was admitted to ICU. In eight patients undergoing HoLEP, five patients undergoing ThuLEP, and five patients undergoing MEP, we observed prostate capsule damage associated with considerable bleeding from the venous sinus (p = 0.26) (Table 4). If intraoperative bleeding control (including electrocautery) failed, a three-way Foley catheter with an irrigation system was placed upon finishing enucleation.

Table 3.

Postoperative Parameters at a 6-Month Follow-Up After Surgery

	IPSS preoperative, score	IPSS postoperative, score	p	QoL preoperative, score	QoL postoperative, score	p	Q_max, preoperative, cc/s	Q_max, postoperative, cc/s	p	PVR preoperative, cc	PVR postoperative, cc	p
HoLEP	21.9 (±1.1)	10.3 (±2.5)	<0.01	4.1 (±0.8)	1.7 (±0.7)	<0.01	7.5 (±1.7)	16.1 (±4.0)	<0.01	72.4 (±28.6)	17.3 (±12.1)	<0.01
MEP	21.5 (±1.3)	11.3 (±3.1)	<0.01	4.0 (±0.8)	1.6 (±0.6)	<0.01	7.9 (±1.8)	16.6 (±3.0)	<0.01	69.5 (±25.4)	18.0 (±11.0)	<0.01
ThuLEP	21.8 (±1.6)	10.9 (±3.0)	<0.01	4.0 (±0.8)	1.8 (±0.6)	<0.01	7.6 (±1.9)	16.2 (±3.3)	<0.01	70.1 (±28.7)	17.3 (±11.7)	<0.01
p	0.19	0.46		0.47	0.09		0.15	0.23		0.62	0.55

Table 4.

Short-Term Postoperative Complications in Patients Immediately Following Surgery

Complication	Treatment	HoLEP (n = 254)	MEP (n = 95)	ThuLEP (n = 202)	p
Clavien–Dindo grade I complications, n (%)
Postoperative bleeding	Prolonged bladder irrigation	3 (1.2)	4 (4.2)	2 (1.0)	0.07
Clot retention	Evacuation of clots through the catheter	12 (4.7)	8 (8.4)	9 (4.4)	0.12
Ureteral orifices' damage	Upper urinary tract stenting/observation	2	0	1	0.41
Clavien–Dindo grade II complications, n (%)
Bleeding, required blood transfusion	Blood transfusion	0	1 (1.1)	0	0.32
Severe urinary tract infection	Prolonged antibiotics therapy (more than 2 weeks)	5 (1.9)	1 (1.1)	3 (1.5)	0.35
Clavien–Dindo grade III complications, n (%)
Incomplete morcellation (due to bleeding)	Repeat morcellation	8 (3.1)	5 (5.2)	5 (2.4)	0.26
Bladder tamponade	Cystoscopy with clot evacuation, coagulation of bleeding vessels	2 (0.8)	1 (1.1)	1	0.47
TURP syndrome	Additional treatment in intensive care unit	0	1 (1.1)	0	0.32

TURP = transurethral resection of the prostate.

The rate of immediate stress urinary incontinence (following catheter removal) (grade I) was 4.3% for HoLEP, 2.4% for ThuLEP, and 5.2% for MEP and decreased to 1.2%, 0.5%, and 2.1%, respectively, 3 months after surgery. Six months after surgery, this rate did not change. In all cases, it was considered mild, occurring only during coughing or sneezing.

Discussion

Our research team determined that HoLEP, ThuLEP, and MEP are all highly effective techniques to alleviate lower urinary tract symptoms, providing equivalent improvement with low perioperative morbidity. The most commonly practiced method of EEP, HoLEP, has shown high efficacy in the treatment of lower urinary tract symptoms caused by BPH.¹ Our research data support this opinion: all 551 patients had improved voiding parameters after surgical treatment, as compared with their preoperative values. Moreover, as evidenced by ultrasonography findings, the prostate volume at 6 months after HoLEP decreased by a mean of 80%.

According to the meta-analysis carried out by Cornu et al.⁵ and our own findings, HoLEP has been shown to have outcomes equivalent to those of transurethral resection and open prostatectomy with a lower complication rate. Moreover, holmium enucleation is preferable because it reduces catheterization and hospital stay times.⁷

The ThuLEP technique, despite its relatively recent advent, also proved efficacious in the treatment of BPH. Note that the wavelength of thulium laser is closer to the water absorption peak.¹⁷ This fact explains two features specific to thulium enucleation: shallow penetration depth not exceeding 2 μm, and a high energy absorption rate that results in instantaneous tissue vaporization.^17
–19 Another important feature of the laser is its operation in continuous wave mode, which allows for excellent hemostasis as well as precise and shallow incisions.¹⁹ This time decrease could also potentially be attributed to the higher level of tissue vaporization during thulium enucleation.¹⁸ All other parameters relating to ThuLEP efficacy were comparable to those of holmium enucleation. We did not observe any significant differences in either mean volume of extracted tissue or prostate volume reduction 6 months after surgery. Our observations led us to the conclusion that urinary tract drainage could be avoided in cases when the ureteral orifice was involved in the enucleation zone; however, ultrasound monitoring was necessary. The damage induced by laser energy in most cases was minor and superficial, which prompted the surgeon to refrain from intraoperatively draining the upper urinary tract.

HoLEP and ThuLEP have been approved by the current guidelines of the EAU for use in men with substantially enlarged prostates (>80 cc) as first-line therapy.¹ However, literature on the subject of EEP that pertains to resection methods besides HoLEP and bipolar enucleation of the prostate are uncommon.^5,7,13

Historically, MEP of the prostate became the first technique to deliver anatomically correct endoscopic enucleation of the gland.² One of the benefits of MEP is that this technique combines the advantages of the standard monopolar instruments with the highly efficient method of endoscopic enucleation which became widespread after the publication by Gilling and Fraundorfer in 1998.⁴ Among the other main advantages of this technique is that it overcomes the problems commonly experienced during TURP, most likely due to TURP's nonanatomical approach to the hyperplastic tissue. During a standard TURP procedure, it may be difficult to determine correct enucleation plane. This may lead to a higher risk of capsular perforation or residual, postoperative adenomatous tissue that may require retreatment. As such, it has been shown that the TURP procedure has a higher rate of retreatment than HoLEP. After TURP technique, roughly 5%–7% of patients have relapse TURP.^1,5,20 Meanwhile, laser enucleation techniques, such as ThuLEP and HoLEP, provide a lower relapse frequency of 1.0%–1.5%.^19,21,22 Although data on recurrent BPH after MEP are absent, we estimate that recurrence rate would be the same as in the laser EEP techniques.

According to our results, MEP time slightly exceeded mean HoLEP and ThuLEP surgery times, but the IPSS and QoL scores were equivalent. It is important to note that while the process of learning the three techniques was simultaneous, MEP was the most difficult. In contrast to laser enucleation techniques with a learning curve of 8–30 surgeries,^23,24 MEP required more surgeries to achieve proficiency. However, this may be caused by higher mean enucleation time in MEP (p < 0.001). This aspect requires further study as the amount of available data on MEP is small.^2,3

It should be noted that postoperative catheterization time after MEP was greater than after ThuLEP and HoLEP due to episodes of urinary retention, which was experienced during the first 10 operations. The rate of clot retention in these initial MEP patients was surprisingly high, occurring in 5 of these 10 cases. These patients required subsequent recatheterization and evacuation of clots through the catheter. In later patients, we decided to keep the catheter within the patient for an additional 1 to 2 days, which effectively led to a decrease in the clot retention rate. In addition, postoperative bleeding necessitating blood transfusion occurred as a consequence of one of the interventions. However, a decline in hemoglobin levels after monopolar transurethral resection is more common than after HoLEP, which may be an indicator of lower-quality hemostasis of electrosurgical techniques.^3,7,25 Moreover, there was no postoperative bleeding that required blood transfusion after laser enucleation, while it was noted in one case (1.1%) after MEP. Despite the fact that its rate was insignificantly higher than in two other techniques (p = 0.6), we had never before encountered such complication during laser EEP at our center. It is also important to note that we observed one case of TURP syndrome after MEP, which we believe may have been caused by a large adenoma (130 cc).

It is worth mentioning than one of the most advantageous aspects of MEP over laser enucleation techniques is that it can be effectively and safely performed with a standard resectoscope equipped with standard monopolar loops, which is basic urologic equipment, common among most medical centers. Thus, MEP of the prostate may be more cost effective than laser techniques, a topic of which we plan on exploring in future studies.

Despite the postoperative complications, the efficacy of all three techniques was comparable. However, there were no significant differences in radicality of surgery, which is indicated by comparable postoperative prostate volume parameters (Table 3). This, in our opinion, makes MEP a suitable and efficacious technique for the management of prostatic hyperplasia >80 cc that may rival other methods of EEP. Moreover, MEP may be performed in almost any setting. While we used a specially designed electrode, this surgery may be carried out with a resection loop and outer sheath of the resectoscope. As mentioned by T.R. Herrmann, the true importance of the procedure is the enucleation technique itself, not the type of energy used for its execution.¹⁴ New methods of EEP are becoming more prevalent and widely accepted for the treatment of prostatic hyperplasia, and a considerable number of varying techniques makes them readily accessible to any hospital.

The limitations that were experienced within our study were its retrospective nature and a differing number of patients operated on using different techniques.

Conclusions

Both ThuLEP and HoLEP proved to be efficacious in the management of BPH allowing for shorter operating times than MEP. Moreover, we did not observe any differences in either catheterization or hospitalization times in the two laser enucleation methods. MEP is a highly promising enucleation technique and was determined to be an effective and acceptable procedure, despite a higher complication rate.

Footnotes

Author Disclosure Statement

All authors state that they have no commercial interests in this article. Also, all authors state that they have no disclosure that might potentially bias their work.

Abbreviations Used

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