A number of laser therapies and surgical techniques have been proposed for the treatment of BPH. Some years ago, Nd:YAG lasers (1,064 nm) were used to deliver a coagulative necrosis in the obstructive prostatic tissue using side-firing laser fibers. Later the same laser was shown to be able to provide ablation of the prostate by placing special fibers interstitially (directly into the tissue) transurethrally. These fibers emitted laser light in a diffuse way along a known length of fiber delivering a coagulative necrosis. Diode lasers (980 nm) were then used in similar techniques.
All BPH treatments involving the delivery of coagulative necrosis suffered from the same drawbacks; long catheterization periods sometimes lasting weeks, significant dyuria following the procedure and delayed realization of clinical benefit. These techniques also involved the somewhat blind delivery of energy into the prostate which is obviously sub-optimal.
Holmium lasers were introduced but the procedure time was long and the removal of resected pieces sometime required the use of a mechanical morcellator. Just an interest in lasers for the treatment of BPH was giving way to microwave and RF ablation therapies, the introduction of a high-powered KTP green light laser revived the enthusiasm for lasers in the treatment of BPH.
The KTP green-light laser provided the important benefit of generally efficient tissue vaporization. The removal of most of the obstructive tissue radically shortened the catheterization period, provided near immediate results that were comparable with TURP but without the high complication rate.
Once laser manufacturers recognized that the market wanted lasers that could quickly and efficiently vaporize prostatic tissue while controlling bleeding, they looked for ways to improve upon the previously offered holmium and KTP lasers.
The result has been the thulium laser. These lasers have wavelengths in the 2,010 to 2,013 nm range. This wavelength is 2.5 times more highly absorbed by water (which accounts for approximately 70% of the content of tissue) compared with the holmium laser and therefore it is highly ablative caused rapid and efficient vaporization while also providing excellent hemostasis. Where holmium energy is delivered in high-powered pulses that create a ragged effect in the tissue and provides sub-optimal hemostasis (40% higher blood loss than thulium laser) , the thulium laser energy is delivered in a continuous-wave providing a smooth, consistent tissue effect.
KTP green-light lasers rely upon hemoglobin as the key chromophore (light absorbing constituent). In well vascularized tissue this works well. In poorly vascularized tissue, the green-light laser does not provide efficient vaporization and instead penetrates deeply into tissue causing a coagulative necrosis. Since the green-light from a KTP laser travels readily through water, the surgeon must take special care to insure that no light is delivered into the bladder. If laser light is inadvertently delivered to the trigone or ureteral ducts significant complications may occur.
So in the long and evolving history of lasers for use in treating BPH, the current leader is the thulium laser such as the Cyber TM™.