Lasers and Stents for the enlarged prostate

Lasers and stents


Lasers

•Light Amplification by the Stimulated Emmision of Radiation
•Flash-lamp with high intensity light bombards resonator cavity with photons
•Electrons excited, decay with emission of photon
•Cascade effect
•Photons leave resonator cavity as coherent laser beam

Principles

•Coherence, collimation and monochromaticity




•Differ with respect to wavelengths, power and mode of emission (pulsed or continuous)


Mechanism of Action
•Heat treatment
o 45-50ºC Desiccation
o 50-100°C Coagulation
o >100°C Carbonisation and Vapourisation
•Effect dependent on power of laser and length of time applied
•NB. Can be used if anti-coagulated or coagulation disorder


Laser types

•Nd:YAG (neodymium, yttrium, aluminium, garnet)
o 1064 nm wavelength
o absorption length in tissue of 0.5 to 1.75 cm, giving it excellent haemostatic properties
o VLAP uses the NF-YAG laser in a non contact mode using a side firing laser
o Contact laser ablation (CLAP) uses NDYAG via a sapphire tipped fibre. Direct contact between laser fibre and tissue causes tissue vaporisation at the point of contact
o CLAP and VLAP show similar improvements at 2 years in flow rates and SS, but at 4 yrs CLAP has a 23% reop rate. CLAP harder to learn, and has been abandoned

•KTP:YAG
o Beam from Nd-YAG passed through a potassium titanyl phosphate crystal (KTP) which doubled the frequency and halves the wavelength (532 nm)
o Good incisional and vaporization properties, with tissue penetration depth of 3mm
o Causes vaporization of tissue, and can result in an immediate TURP like channel

•Ho:YAG
o Wavelength of 2140 nm
o Penetration depth of only 0.4mm, with excellent incisional and haemostatic properties
o Laser ablation of prostate involves vaporization of prostate tissue using a side firing fibre
o Laser resection of the prostate divides the lobes into fragements small enough to irrigate from the bladder
o Laser enucleation of the prostate, whole lobes cut away, and then morcellated for removal

•Diode
o Wavelength of 830 nm
o Used for interestitial laser coagulation
o Coagulation necrosis occurs via a fibre inserted directly into interstitium of prostate
o Usually needs spinal or GA


Methods

Side-firing
TRUS guided Laser induced Prostatectomy (TULIP)
Visual laser ablation of the Prostate (VLAP)
Interstitial Laser Coagulation (ILC)
Ho laser resection of the prostate (HoLRP)


TULIP

‘Blind’
Side-firing Nd:YAG
Useless
Abandonded

Visual laser ablation of the Prostate (VLAP)

Mixture of coagulative necrosis and vapourisation
Nd:YAG laser(1064nm) at 40-90W for 60s
Quadrant / Sextant spot application technique via cystoscope
Tissue sloughs away
Results
85% have ³ 50% improvement in SS or Qmax
Significant reduction in BOO (80-95%)
No irrigation required
Best if gland < 50-60g
Not suitable if UTI / bacterial prostatitis
Complications
Prolonged catheterisation (3-4 weeks) & dysuria
Serious complications in 12%
Impotence 0%
Incontinence 0%
Urethral stricture 2%
Bladder neck contracture 4%
Ret ejaculation 22%
Retreatment rate 2%/year (Costello) – 8%/year (Puppo)


Interstitial Laser Coagulation (ILC)

Coagulation necrosis used to reduce prostate volume
Secondary atrophy & regression of prostate rather than sloughing
Nd:YAG or diode laser
Fibres placed into prostate tissue cystoscopically
1-2 fibres per 5-10ml prostate volume
Results and complications
Similar improvement in LUTS & BOO to TURP at 1 year follow-up (Muschter)
8% ILC subsequently required TURP
Mean catheterisation – 18 days
Complications
Ret ejaculation 12%
Stricture 5%
Impotence 0%
Incontinence 0%
Retreatment 3%/year for first year rising to 10%/year subsequently

Ho laser resection of the prostate (HoLRP)

Pulsed solid-state laser, l = 2140nm
Ho:YAG l is strongly absorbed by water
Zone of coagulative necrosis, 3-4mm, is adequate for haemostasis
Peak power causes intense vapourisation and precise cutting
550mm end-firing quartz fibre via continous flow resectoscope with normal saline irrigant
80W Ho:YAG laser
Results
Gilling et al (J Urol 1999; 162: 1640) Prospective RCT, TURP v’s HoLRP with 1 year follow-up
Similar improvements in SS, Qmax and PdetQmax
Complications
Dysuria 10%
Impotence 0%
Ret ejaculation 75-80%
4 yr follow up: J Urol 2004. Similar outcome to TURP with less morbidity

Stents

10-15% BPH patients unfit for surgery
AUA guidelines: only for use in unfit pts
A number of small studies using prostatic stents in unfit men with retention
Various materials used
Metallic alloys, bioresorbable, polyurethane, thermosensitive
Urolume
Self-expanding superalloy wire
Placed cystoscopically or US guided
Over a few weeks to a few months they become covered with normal transitional epithelium

Urolume North American Clinical Trial
13% required stent removal
Side effects
Urgency (67%), dysuria (50%), perineal pain (50%), persistent retention (10%), incontinence (<1%), haematuria, encrustation, occlusion,
TITAN Stent
Seamless titanium tubing
Expanded with non-compliant balloon
Placed cystoscopically with iv sedation & prostate block
Results inferior to Urolume