Comparison of GreenLight Laser Photoselective Vaporization and Thulium Laser Enucleation for Nonmuscle Invasive Bladder Cancer

Abstract

Objective: To evaluate the safety and efficacy of GreenLight laser vaporization and thulium laser enucleation for nonmuscle invasive bladder cancer (NMIBC). Patients and methods: A total of 150 patients of NMIBC who underwent either GreenLight laser vaporization (Group A, n = 78) or thulium laser enucleation (Group B, n = 72) were analyzed, respectively. The preoperative, intraoperative, and postoperative clinical data were recorded and compared in the two groups. Results: All patients were successfully treated with GreenLight laser vaporization or thulium laser enucleation. No significant difference was observed in operation time, catheterization time, and postoperative hospital stay time between them. No complications such as obturator nerve reflex, bladder perforation, overhydration, or intraoperative or postoperative bleeding occurred in all patients. The patients were followed up for 12 months; during the period the recurrence rate was 10.26% (8/78) and 9.72% (7/72), respectively, between Groups A and B. Conclusions: Both GreenLight laser vaporization and thulium laser enucleation are effective and safe treatments for patients with NMIBC. Long-term clinical trials are necessary to increase the current scientific evidence base.

Introduction

Bladder cancer is one of the most common malignant diseases in urinary system.¹ The American Cancer Society estimates that 79,030 new bladder cancer cases and 16,870 bladder cancer-related deaths occurred in 2017.² About 75% of bladder cancer patients have nonmuscle invasive bladder cancer (NMIBC), which is confined to TaT1 or carcinoma in situ.³ Although transurethral resection of bladder cancer (TURBT) is the gold standard treatment commonly used for NMIBC patients, this surgical procedure has risks. Potential risks include obturator nerve reflex during surgery, particularly for lesions located on bladder sidewall, which can lead to bladder perforation and absorption of hypotonic fluid, resulting in electrolyte imbalance or transurethral resection syndrome.⁴ In addition, TURBT may increase the risk of bleeding and cardiac arrhythmia in patients taking long-term oral anticoagulant therapy due to cardiovascular diseases.⁵ Thus, in this case, alternative surgical strategies, such as laser ablation, may have therapeutic advantages. In the current study, we evaluated the merits of GreenLight laser vaporization for NMIBC compared with thulium laser enucleation in terms of preoperative, intraoperative, and postoperative clinical data.

Patients and Methods

Patients

From April 2013 to December 2016, 150 NMIBC patients were enrolled in the present study; all patients were randomly selected. Patients with primary tumors and tumor diameters of <4 cm were included in the criteria. Each patient's pathology was confirmed to be NMIBC with no carcinoma in situ. All patients were provided with written informed consent before surgery, and they chose their own surgical procedures by themselves. Exclusion criteria include bladder cancer with distant metastases, locally advanced bladder cancer, muscle invasion bladder cancer, and/or concomitant benign prostatic hyperplasia. The present study was conducted under approval of the Institutional Review Board of the Second Affiliated Hospital of Soochow University (Suzhou, China).

Preoperative diagnosis can be made by medical history, physical examination, ultrasound, and pelvic computed tomography. Further, urine cytology, cystoscopy, and biopsy were routinely performed to diagnose and pathologically characterize the bladder cancer before operation. All patients were retrospectively collected and classified into two groups: GreenLight laser vaporization (Group A, n = 78) and thulium laser enucleation (Group B, n = 72).

All patients were in the lithotomic position under general or continuous epidural anesthesia. The operation was performed by a 25.6F continuous flow resectoscope, and normal saline was used for continuous irrigation. The bladder was examined thoroughly, the ureteral openings on both sides were observed, and then the size, location, shape, and number of tumors were recorded carefully. Baseline characteristics of all patients are listed in Table 1; no significant differences were observed between the two groups (p > 0.05).

Table 1.

Baseline Characteristics of Patient Clinical Features of the Two Groups

	GreenLight laser vaporization (Group A)	Thulium laser enucleation (Group B)	p
Gender (n = )	78	72
Male	58	57	>0.05
Female	20	15	>0.05
Mean age (years)	66 ± 9.3	68 ± 10.8	0.30
Mean tumor multiplicity (n = )	1.30 ± 0.65	1.26 ± 0.63	0.77
Mean tumor size (cm)	1.92 ± 0.92	1.82 ± 0.84	0.48
Tumor location
Lateral wall	65	62	>0.05
Other site	13	10	>0.05
Histopathology
Ta	46	43	>0.05
T1	32	29	>0.05
Grade
Grade 1	64	60	>0.05
Grade 2	14	12	>0.05

GreenLight laser vaporization

The equipment and surgical procedure used for Group A were previously described by Yang et al.⁶ First, the GreenLight laser fiber was inserted into the working channel. Second, the laser vaporization power was set to 80–120 W, and the laser coagulation was set to 30–40 W. Then, the resection was executed 1.0 cm away from the visible tumor edge and down to the deep muscular layer of the normal bladder wall. After exposure of the deeper detrusor muscle, careful vaporization of the underlying muscle and surrounding mucosa was performed. Then, floating tissues were retrieved using an Ellik Evacuator, and a catheter was indwelled.

Thulium laser enucleation

The equipment and surgical procedure used for Group B were previously described by Liu et al.⁷ First, the thulium laser fiber was inserted into the working channel. Approximately 30–50 W of power was chosen for most of the procedure. Then, the bladder mucosa was cut and vaporized 1.0 cm away from the base of the tumor up to the muscle layer. With the aid of the laser fiber, the tumor and the muscle tissue of the band were lifted and removed from the root. If the tumor was difficult to flush out, the tumor body was cut by the laser, and an extractor was used to wash out specimens for pathological diagnosis. Then, vaporization of the underlying muscle and surrounding mucosa was carefully completed. After verifying that there was no perforation or hemorrhage, a catheter was indwelled.

Results

Baseline characteristics of patients are listed in Table 1. Clinical features were compared by gender, age, tumor multiplicity (the number of tumors), tumor size, tumor location, histopathology, and tumor grade in Groups A and B. No significant differences were found between the two groups (p > 0.05). Intraoperative and postoperative data are listed in Table 2. All operations were successfully performed. The mean operative time was 25.96 ± 3.88 min in Group A and 24.97 ± 3.85 min in Group B. The mean catheterization time was 48.08 ± 8.38 and 48.32 ± 8.86 h in Groups A and B, respectively. No significant intraoperative or postoperative complications occurred in either of the groups (Clavien–Dindo classification, Grade I). No patient required blood transfusion or experienced obturator nerve reflex, vesical perforation, or urine extravasation.

Table 2.

Intraoperative and Postoperative Characteristics of the Two Groups

	GreenLight laser vaporization (Group A)	Thulium laser enucleation (Group B)	p
Mean operation time (min)	25.96 ± 3.88	24.97 ± 3.85	0.12
Mean catheterization time (h)	48.08 ± 8.38	48.32 ± 8.86	0.86
Obturator nerve reflection	0	0	—
Complications (Clavien–Dindo)
Grade I	78	72	—
Grade II	0	0	—
Grade III	0	0	—
Grade IV	0	0	—
Grade V	0	0	—
Recurrences (n = )	8	7	>0.05

Postoperative intravesical instillation was performed for each patient. Patients began weekly administration of 50 mg of epirubicin after surgery for 8 weeks, and then this therapy was managed every month for the next 4 months. Ultrasonography and cystoscopy were performed every 3 months after operation in all patients. At 12-month follow-up, 8 of 78 patients (10.26%) in Group A and 7 of 72 patients (9.72%) in Group B had recurrence.

Discussion

Although TURBT remains the gold standard of treatment for NMIBC, there is a growing interest in using lasers for NMIBC. Laser therapy for bladder cancer was first reported in 1970 and approved for clinical use in 1984.⁸ Since then, many kinds of lasers have been used for urological surgery, such as holmium, GreenLight, and thulium lasers.^1,9

The GreenLight laser [also referred to as a potassium-titanyl-phosphate (KTP) laser] emits a wavelength of 532 nm by converting the wavelength of light emitted from a Nd:YAG laser (1064 nm) with KTP cystine.⁵ This wavelength of light is highly absorbed by hemoglobin and minimally absorbed by water, which limits the optical penetration depth of the laser to 0.8 mm. After laser excitation the heat remaining in the tissue induces a coagulation zone of only 1–2 mm thickness, thereby effectively preventing serious bleeding and/or bladder perforation in Group A patients.⁶ Because this laser beam has a forward deflection of 70° and a divergence angle of 15°, vaporization of tumors located in special sites, such as the lateral bladder wall or near the ureter orifice, can be performed successfully.^6,10

In contrast, the thulium laser has a center wavelength between 1.75 and 2.22 μm, which precisely matches the 1.94 μm water absorption peak in tissue.¹¹ Since this continuous wavelength has the advantages of high resection rate and predominate hemostasis, it was widely used for TURBT.¹² Further, the thulium laser can completely excise the tumor en bloc with the basement membrane to provide sufficient tissue which is favorable to assess tumor recurrence and prognosis in further therapy.^13,14

Our results showed that both GreenLight laser vaporization and thulium laser enucleation could effectively resect NMIBC tumors. Due to their short penetration depths and hemostatic properties, both lasers allow for precise, controlled, and safe excision of tumors with an almost bloodless operation field. Further, manual administration of physiological saline as an irrigating agent without electrical effect avoided obturator nerve reflex and bladder perforation. Hence, there were few intraoperative and/or postoperative complications, and recurrence was low. Therefore, the results of our study indicate that both GreenLight laser vaporization and thulium laser enucleation are effective and safe treatments for patients with NMIBC. Long-term clinical trials with more patients are necessary to confirm these results.

Footnotes

Acknowledgments

This study was supported, in part, by the Natural Science Foundation of Jiangsu Province (Grant No. BK20160339), the Science and Technology Projects Foundation of Suzhou City (Grant No. SYS201547), and Natural Science Foundation of Suzhou University (Grant No. SDY2015A17) of China.

Author Disclosure Statement

No competing financial interests exist.

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