Development of Medical Lasers for Treatment on Benign Prostatic Hyperplasia.

Benign prostatic hyperplasia (BPH) is one of the most common causes of lower urinary tract symptoms in aged males. Many patients with BPH may go on to require surgical intervention. At present, transurethral resection of the prostate (TURP) is the gold standard for BPH treatment owing to its minimal damage, low cost, and long-term efficacy. However, many complications associated with TURP represent major drawbacks of this procedure. These complications include hemorrhage, perforation of the prostatic capsule, urinary incontinence, retrograde ejaculation, urethral stricture, bladder neck spasm, transurethral resection syndrome (TURS), and more. The incidence of long-term complications is 32.14%.[1] TURS is one of the most serious complications with an incidence of 2%.[2] TURS can lead to death if not treated promptly. Due to the high incidence of complications, surgical treatment with TURP has been limited.

With the development of the medical techniques, medical lasers are emerging as new treatments for BPH. Medical lasers include holmium laser, green laser, 1470 nm diode laser, 980 nm diode laser, 2 μm continuous wave (CW) laser, and others. One advantage of medical lasers for BPH treatment is no existence of TURS. In addition, it is a convenient operation, with minimal bleeding and a short hospital stay. The surgical treatment of laser vaporesection for BPH treatment is gradually accepted by clinicians due to its apparent advantages.[3] This study is aimed to introduce the development of medical lasers used to treat BPH.

MEDICAL LASERS

Holmium:YAG laser

The wavelength of holmium:YAG laser is 2140 nm and its penetration depth in tissue is only 0.4 mm. The area of heat damage ranges from 0.5 to 1.0 cm when the holmium:YAG laser works. The holmium:YAG laser is an ideal tool for cutting tissue due to the characteristics listed above.[4]

Holmium laser enucleation of the prostate (HoLEP) is the classic clinical surgical treatment for BPH by using holmium:YAG laser. It was first reported in 1998.[5] During the operation of HoLEP, the prostate is removed completely and pushed into the bladder. The prostate tissue is removed from the bladder using a prostatic tissue morcellator. HoLEP has such advantages as quick recovery, little bleeding, short hospital stay, and more. TURS does not occur because the irrigating fluid is normal saline during the operation. Regarding the treatment of prostates greater than 100 grams, a randomized controlled trial comparing HoLEP to open prostatectomy (OP) showed a shorter time in hospital stay after HoLEP (70 vs. 250 h, P < 0.01) and a lower rate of blood transfusion (0% vs. 13.3%, P < 0.01).[6] When the prostate over 60 grams was treated, a randomized controlled trial showed less blood loss during HoLEP than that during TURP (0.47 ± 0.46 vs. 0.63 ± 0.6 g/dl, P < 0.05).[7] A study analyzed the 12-month outcome of low-powered HoLEP (LP-HoLEP) for patients with symptomatic benign prostatic obstruction (BPO) showed that maximum flow rate (Qmax) (12 vs. 29.3 ml/s), postvoid residual (PVR) urine volume (155.00 vs. 11.15 ml), International Prostate Symptom Score (IPSS) (22 vs. 6), and quality of life (QoL) score (5 vs. 1) had improved significantly (all P < 0.001) at the 12-month follow-up period.[8] The operation of HoLEP showed excellent results for BPH patients with anticoagulant therapy or with bleeding disorders.[9] Some scholars reported that HoLEP had such several shortcomings as longer learning curve and a longer operation time.[10] However, this technology has been improved, and the time of the learning curve has been reduced.[11]

Thulium vapoenucleation of the prostate (ThuVEP) is another method for BPH treatment using the holmium:YAG laser. A study retrospectively assessed the 5-year outcomes of ThuVEP in patients with BPO. The result proved that ThuVEP was a durable procedure with regard to improvement on micturition and reducing of PSA, as well as the reintervention improvement on rate after ThuVEP during long-term follow-up.[12] ThuVEP is a safe and effective procedure for the treatment of symptomatic BPO as HoLEP. Both procedures produce equivalent and satisfactory immediate micturition improvement with low perioperative morbidity.[1314]

Green laser

The wavelength of green laser is 532 nm, which has a tissue penetration depth of 0.8 mm. One of the advantages of green laser is its effective result in controlling bleeding. The maximum power of the green laser is 180 W, which was first introduced in 2011.[1516]

The green laser for BPH treatment is named photoselective green laser vaporization of the prostate (PVP). The operation of PVP has advantages of little bleeding, quick recovery, short hospital stay, no TURS, and a short learning curve time.[17] The hemostasis of green lasers is excellent, which allows PVP appling to patients of BPH with anticoagulant therapy.[18] PVP also applies to large-volume prostate patients. A study was performed to evaluate the results of GreenLight XPS photovaporization (PVP/XPS) with intraoperative transrectal ultrasonographic monitoring for the treatment of large BPH, with volume >80 ml. The results showed that there was a significant improvement in IPSS (4.0 vs. 19.5), QoL score (1 vs. 5), Qmax (19.1 vs. 8.2 ml/s), and PVR (26 vs. 100 ml) (all P < 0.001). Furthermore, the treatment of large BPH with PVP/XPS is safe and effective.[19] A study comparing PVP to OP on large volume prostate (>80 ml) showed a shorter hospital stays after PVP than after OP (48.00 vs. 0.44 h, P < 0.05) and a lower rate of blood transfusion (0 vs. 13%, P < 0.05).[20] Another study comparing PVP to TURP showed a shorter catheterization time (1.25 vs. 4.67 d, P < 0.01) while PVP showed a higher rate of symptomatic relief after 1 year of follow-up (45.6% vs.18.2%, P < 0.01).[21] The study of calves model had established the long-term durability of PVP for the treatment of BPH. The rate of reoperation was 4.8% in a follow-up of 57 months.[22] Another study showed PVP to be an effective, safe, and durable treatment for men in acute urinary retention (AUR) with a catheter-free rate of 96%. The improvement of symptoms was similar to those who did not present in AUR.[23]

Two μm continuous wave laser

Two μm CW laser is also known as thulium laser, which has a wavelength of 2013 nm and a penetration depth in tissue of 0.3 mm. Two μm CW laser has an excellent cutting capacity similar to holmium:YAG laser and also has better hemostasis similar to the green laser. Operations using 2 μm CW laser has such advantages as minimal bleeding, short operation time, quick recovery, short hospital stay, few complications, and more.[24]

The method of using 2 μm CW laser for treating BPH includes 2 μm (thulium) laser resection of the prostate-tangerine technique (TmLRP-TT), and 2 μm (thulium) laser enucleation of the prostate (ThuLEP).[2526] A prospective analysis of 51 patients with previously negative transrectal prostate biopsies, who underwent surgical treatment using TmLRP-TT showed that the mean IPSS, QoL score, Qmax, and PVR, changed notably in a 6-month follow-up period (22.5 ± 6.9 vs. 6.1 ± 3.2, 4.8 ± 1.3 vs. 1.1 ± 0.9, 7.3 ± 4.5 vs. 18.9 ± 7.1 ml/s, and 148.7 ± 168.7 vs. 28.4 ± 17.9 ml; all P < 0.001).[27] ThuLEP offers complete removal of the transition zone regardless of the size of the prostate and produces good clinical results when comparing ThuLEP with OP or TURP.[28]

A new method for BPH treatment, named the “five-part method” of 2 μm CW laser vaporesection, was reported.[29] This method is named “five-part method” because the entire prostate is separated into five parts. During the operation, the urethral sphincter is easily distinguishable, which results in a reduced rate of incontinence. The method is easy to master for beginners with advantages of safety, simplicity, short operation time, short hospital stay, and little bleeding. “Five-landmark grooves” of 2 μm CW laser vaporesection was reported in 2014.[30] This method separated the prostate into three parts using five-landmark grooves and achieved good results.

Diode laser

Diode laser has an excellent cutting capacity and produces good hemostasis similar to the 2 μm CW laser, which has been used for BPH treatment in recent years. The wavelength of commonly used diode lasers are 980 and 1470 nm. The operation used diode laser has such advantages as little bleeding, quick recovery, short hospital stay, few complications, and more.[3132] The straight light and lateral light of the 1470 nm diode laser make the operation process more easier compared with those of Holmium:YAG laser and 2 μm CW laser.

The method of using a diode laser for treating BPH includes diode laser enucleation of the prostate (DiLEP) and diode laser vaporization of the prostate. A report showed all the 17 patients who underwent the operation using DiLEP were discharged from the hospital 24 h after the operation. The improvement in the IPSS (22.3 ± 4.1 vs. 7.1 ± 1.06, P < 0.05) and in the Qmax (7.14 ± 2.6 vs. 21.4 ± 3.6 ml/s, P < 0.05) was sustainable after three months of follow-up.[33] Another study compared the outcomes of diode laser vaporization of the prostate to that of TURP showed diode laser vaporization offered a safer and more feasible option in the management of patients with symptomatic BPH.[34]

A new method for BPH treatment, called the “honeycomb” evaporation technique uses a straight light beam (a 1470 nm laser), was reported in 2015. The report showed that the mean IPSS, QoL score, Qmax, and PVR, changed notably in a 3-month followup period (26.0 ± 1.9 vs. 9.6 ± 1.6, 6.0 ± 0.6 vs. 2.7 ± 0.5, 6.9 ± 1.7 vs. 16.8 ± 4.4 ml/s, 163.7 ± 19.9 vs. 20.1 ± 9.6 ml; all P < 0.05).[35]

SUMMARY OF MEDICAL LASERS

Medical lasers have the advantages of little injury, strong hemostatic effect, quick cutting speed, and ease of use. Operations that use medical lasers have the advantages of producing little bleeding, quick recovery, short hospital stay, no TURS, and fewer complications. Complications of medical lasers include secondary hemorrhage, urethral stricture, urinary incontinence, and decrease of sexual function. Kim et al.[36] reported that HoLEP did not influence overall sexual function including erectile function.

During operations on BPH, different kinds of medical lasers have their own disadvantages. The holmium:YAG laser has a perfect cutting effect; however, its hemostatic effect is poor. The green laser has perfect hemostatic effect; however, the speed of vaporization is slow, and pathological specimen cannot be obtained during the operation. The 2 μm CW laser and diode laser both have perfect cutting effect and hemostatic effect; however, it is difficult for the two kinds of lasers to cut the large middle lobe of the prostate protruding into the bladder. The other disadvantage of medical lasers is that the equipment is expensive, meaning that fewer hospitals can afford them.

Which is the best medical laser? The Holmium:YAG laser has the best cutting capacity and the green laser has the best vaporized hemostatic function. The 2 μm CW laser and diode laser have both functions, but the 1470 nm diode laser is better than the 2 μm CW laser. The methods of using medical lasers for the treatment of BPH include HoLEP, PVP, TmLRP-TT, DiLEP, and more. Which is the best method? A clinical research addressing this issue showed that every method has its own advantages.[37] Doctors should choose the most appropriate method that they can do their best.

CONCLUSION

Medical lasers have not been used widely due to their high price and because TURP is still considered the standard of BPH treatment. With the increasing health expenditure, medical lasers will be increasingly used in the clinic because of their advantages. In the future, operations using medical lasers for BPH treatment may replace TURP and become the new gold standard.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.