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ARTICLES |
INTRODUCTION
This article reviews the range of laser techniques available for the treatment
of prostatic disease, in particular benign prostatic enlargement (BPE) and prostate
cancer. Each modality will be briefly introduced, the mechanism of action and
recent experience reviewed and an assessment made of the current and future
role of each.
Benign enlargement of the prostate (BEP)
A quarter of the male population above 40 and 43% of men between 60-69 years,
have lower urinary tract symptoms (LUTS) in the presence of a reduced urinary
flow rate and an enlarged prostate. 1 Approximately 10-15% of the UK male population
will be considered for prostatic surgery at some point in their lives2. Men
of 40 years of age in the United States in 1990 appeared to have a 30-40% chance
of undergoing prostatectomy if they survived to 80 3 though age-adjusted rates
of TURP reached a peak in 1987 and have dropped substantially since as a result
of alternative treatments and the onset of “managed care”4.
TURP is regarded as the gold standard in the treatment of bladder outlet obstruction
(BOO) secondary to BEP. Immediate relief of symptoms is usual, morbidity acceptable
and mortality low5. However, TURP may be associated with long term cardiovascular
side effects6 and complications such as impotence7,8and retrograde ejaculation.
Consequently there has been growing interest in alternative methods of treatment.
This began with microwave therapy and advanced with the development of laser
methods. There has now been a return to thermoelectric methods (electro vaporisation)
utilising much higher energy levels than used for TURP.
Prostate cancer
Prostate cancer is the commonest cause of death from malignancy in men in the
western world. The main impact of the disease is on older men, 95% of all cases
and more than 97% of prostate cancer deaths occurring in men aged 60 and above.
Radical prostatectomy or radiotherapy are the de facto primary options for younger
men with apparently localised disease in much of the world. Safer or less invasive
alternatives or adjuvant therapies will always excite interest. Microwave heating
was initially introduced as a treatment for prostate cancer9 then attention
turned to BEP10. Cryotherapy, having been explored for BEP in the 1970’s11,
has enjoyed a recent revival of interest as an option for prostate cancer12.
Focussed ultrasound13 and “Pyrotherapy”14 have potential roles for
both benign and malignant prostatic disease. Laser methods initially involved
a secondary Neodymium-Yttrium Aluminium Garnet (Nd-YAG) laser coagulation of
the prostatic cavity remaining after a “radical” or at least extensive
endoscopic resection of the inner prostate15,16, then attention moved to interstitial
methods, using the ultrasound techniques developed for radioactive seed implantation17,18
and now photodynamic methods are being actively investigated for both prostate
cancer19-23 and for benign prostatic disease24.
Thermal therapies in general
When tissue is heated there may be minor tissue effects at tissue temperatures
between 40 and 44 °C (designated as "Hyperthermia") particularly
within malignant tissues25 . But as tissue is heated more (by whatever means)
irreversible cellular damage occurs above 45°C. The reciprocal relationship
between tissue temperature and duration of heating suggests that if the temperature
of target tissue is raised by a few degrees above 45 oC then a cytotoxic effect
will be achieved with a much shorter exposure time26. Coagulation necrosis occurs
with small and then larger vessel thrombosis leading to later sloughing and/or
reabsorbtion of necrotic tissue at temperatures at or above 60°C and vaporisation
with acute disruption of tissue due to steam formation occurs at 100°C.
Higher temperatures are associated with tissue burning, carbonisation and some
immediate tissue removal and tissue disruption due to volatile gas formation.
Non thermal laser methods
Photodynamic Therapy (PDT)
PDT involves the use of pure light wavelengths to activate previously administered
photosensitising agents to cause cell injury by a non-thermal mechanism. Ideally
the photo-sensitising drug is taken up or retained to a greater degree by the
target tissue than by other tissues. The precise mechanism by which the tumour
cells are killed is unclear but probably involves the liberation of oxygen radicals
and toxic effects on small blood vessels. 27 In practice there may be a thermal
component in some circumstances and there is the possibility of combining PDT
and thermal therapies in future. Currently PDT has been more explored as a therapy
for prostate cancer rather than for BEP.
Any source of light of the appropriate wavelength and power output may be used
for PDT. Endoscopic illumination or interstitial application of the light are
both possible. Experiments have been stimulated by the “transparency”
of the prostate to certain wavelengths.20 Red light (630 nm) penetrates prostate
deeply. PDT has several potential advantages over endoscopic or interstitial
laser thermal coagulation.: tissues necrosed by PDT heal with more regeneration
and less scarring than after thermal damage so there may be less long term impairment
of function .28 It is therefore possible to selectively damage tumour areas
whilst preserving adjacent normal tissue exposed to the same sensitizer and
light dose, though this requires careful manipulation of parameters . However,
systemic exposure to the older, 1st generation photosensitzing agents such as
haematoporphyrin derivative can lead to problems, particularly cutaneous photosensitization.
Earlier work using Dunning R 3327 rat prostate cancer cells implanted in Copenhagen
rats showed reduced tumour growth in those animals exposed to a photosensitizer
and subsequently to red light given interstitially by either single or multiple
fibres implanted within the tumour 29though it is possible that a combination
of thermal and PDT effects were responsible. A similar effect was shown in vitro
where photosensitized Dunning R 3327 cells were killed by exposure to red light
at a level that precluded any thermal effects on the cells.30
In the first clinical experience of PDT in the treatment of human prostate cancer
Windahl et al.21performed an extended TURP in two patients and then gave a photosensitizer.
48-72 hours later they illuminated the prostatic cavity with 628 nm light through
a fibre with a spherical tip. Neither suffered adverse local effects or any
of the urgency usually reported following PDT of the bladder. Subsequent biopsies
were free of tumour. PSA levels fell from 10 and 6mgm/L to 2.5 and 0.2 mgm/L
respectively. One man died of lung cancer and at post mortem was found to have
no remaining prostatic cancer. As with endoscopic PDT for bladder cancer and
other hollow organ cancers of the body, the most appropriate combination of
sensitizer dose and light dose is still being explored.
Increasingly canine prostate experiments have suggested a role for newer photosensitisers
such as the chlorins 22 and disulfonated aluminum phthalocyanine (AlS2Pc) and
5-aminolevulinic acid (ALA) -induced protoporphyrin IX. ALA appears to produce
small volume effects but AlS2Pc caused more extensive glandular damage while
preserving the supporting stromal tissues23.
Possible roles for PDT in prostate cancer may be:
1. For the adjuvant “mopping up” of possibly abnormal tissue just
beyond the extent of high temperature or cryotherapy lesions to aid completeness
of treatment.
2. To allow treatment of multifocal tumour, probably by means of a multi-fibre
interstitial method.
3. For local PDT of an abnormal focal area of prostate, probably by a percutaneous
interstitial 1-4 fibre method.
4. By an endoscopic approach, either using a modified fibre or a balloon designed
to give adequate and even illumination of the prostatic cavity. This method
may be suitable for the man in whom the diagnosis of prostate cancer is made
following a TURP.
Laser Thermal Methods
Uptake of laser methods has been rapid but it is important to remember that
there are still few properly powered randomised controlled trials (RCTs) from
which informed judgements can be made in this evolving subject. Table
1 shows a range of published laser RCTs. Early data on short- term mortality,
morbidity, complication rates and outcome is available but we await further
details of cost- effectiveness, long- term outcome and patient preference.
Laser Characteristics and Tissue Effects:
When laser light strikes tissue energy is deposited and tissue is heated. The
amount and rate of energy delivery and the degree to which a particular laser
wavelength is reflected, absorbed, scattered or transmitted through the target
tissue will determine the nature of the thermal process. The power density (PD,
the laser power divided by the surface area of the irradiated spot if the laser
beam was firing perpendicularly at a flat surface and described as W/cm2) determines
the rate of energy and therefore heat deposition onto the target tissue surface
(for endoscopic, free beam methods). The Neodymium- Yttrium Aluminium Garnet
(Nd:YAG) laser or small, compact Diode lasers with wavelengths causing similar
tissue effects (805-980 nanometres) are used for coagulating BPH. Potassium
Titanyl Phosphate (KTP) or Holmium lasers (2140nm) produce more avidly absorbed
laser wavelengths and have more obviously superficial vaporising and disruptive
effects (and so can cut tissue). The same device (or wavelengths) can be used
either closer to the tissue to create a high PD with a tendency to a disrupting
or “vaporising” effect or held further away to achieve a primarily
coagulating effect as desired.
Laser light has been applied to the prostate by a series of techniques (Table
2). These methods all show effective prostatic tissue destruction in the
largely glandular canine model. However the human gland is far more resistant
to heating (by any method). Differing epithelial:stromal ratios could explain
differences in response31. Prostatic needle biopsies and transrectal ultrasound
(TRUS) images from human laser “failures” had lower epithelial:stromal
ratios (1:5) than “successes” (1:3.3) and a more homogeneous Transition
zone on TRUS32 raising the possibility of selecting patients for any heat based
treatment by TRUS or biopsy.
1) Transurethral endoscopic beam from a simple “bare” fibre:
This is the most basic method of laser surgery to the prostate. The Nd:YAG laser
was first widely used in this way during open surgery and then applied to endoscopic
surgery. Initially the intention was to achieve coagulation of the target tissue
(usually the prostatic lateral lobes33). When more powerful Nd:YAG laser generators
or more obviously vaporising wavelengths became available (e.g. Argon, KTP34
and most recently Holmium:YAG35) the techniques of localised vaporisation or
cutting of the prostate or bladder neck tissue developed. The simple transurethral
endoscopic “bare” fibre is by far the cheapest laser option since
no specialised equipment is used but may result in more urethral injury due
to the extra manipulation needed to reach all the adenoma. 36
Mattioli37 reported an ingenious mirror adaptation of the albarran lever that
deflects the beam from a bare fibre to achieve coagulation of the prostate.
He reported efficacy and that this was a reuseable and cost effective device.
No further follow up reports are available.
The Holmium:YAG laser fired through a fine fibre close to the tissue surface
can cut tissue by vaporisation and can achieve coagulation when held at a distance
(or by using a beam deflecting device) thus reducing the power density at the
point of beam impact . Development has been rapid: initially the Holmium was
used simply as a vaporising addition to Nd:YAG laser coagulation38 but this
method was rapidly replaced by purely Holmium vaporisation of the prostate39
or cutting of the bladder neck40 . Now a technique of incising and mobilising
the prostatic lobes in a manner similar to resection41 ( intuitively familiar
to most urologists) is commanding most attention.
A bare fibre optimised to carry the holmium wavelenght is protected by a covering
ureteric catheter and is passed down a urological endoscope to the prostate.
The fibre tip and beam is used to “resect” chunks of the prostatic
adenoma from the prostatic capsule. Removing the relatively large pieces of
prostatic tissue remains a problem and the protagonists of this development
recognise the need to utilise some form of tissue “morcellator” to
allow efficient removal of the tissue debris. However, even with these limitations,
the early results are very comparable to TURP41 with early catheter removal
and minimal postoperative dysuria.
It would be interesting to know the endoscopic and certainly the ultrasonic
appearances of these glands after Holmium resection and it is still not clear
where all the tissue goes since a relatively small proportion is resected and
it is assumed that a similar amount is “vapourised”.
2) Contact laser method: Transurethral endoscopic fibre with a specialised
“contact tip”.
The direct application of laser heated probes ( usually synthetic sapphire contact
tips, CTs ) is intended to remove enough tissue immediately to allow unobstructed
postoperative voiding. The quality of data on CT methods has been strengthened
by the Oxford laser prostate trial 42,43 , a double blind RCT of contact tip
methods versus TURP which is a good example of a study designed with appropriate
statistical powers.
There were no statistically significant differences between the 2 arms in terms
of the 7 question American Urological Association symptom score (AUA7SS) response
or flow rates at 3 or at 12 months follow up. Other parameters (blood loss,
hospital stay and length of catheterisation) favoured the CT laser arm. but
significantly more men achieved a large change in AUA7SS (8 pts or more, perceived
by the patient as a marked improvement) following TURP.
Catheters were removed 1 night after laser and 2 nights after TURP. Seventeen
(28%) men in the CT laser arm failed to void after removal of the catheter compared
to 8 (12%) in the TURP arm which suggests that CT methods may allow earlier
voiding than coagulative techniques but a significant proportion will still
have delay ed voiding . The reoperation rate was 6.6% in the TURP group vs 18.4%
for CT laser. An economic evaluation of the Oxford CT laser prostate trial suggests
TURP will remain more cost effective than CT laser methods until the cost of
laser consumables is reduced. This well designed study will presumably provide
outcome data over the longer term and it may be 5 yrs before we really know
the overall failure or retreatment rates which will define the cost effectiveness
of this and all other new techniques.
3) The interstitial application of laser energy using a “bare” or
modified fibre.
Inserting a small, relatively atraumatic fibre into the prostatic tissue either
transurethrally, transrectally or percutaneously under US guidance and heating
it up directly (interstitial laser coagulation or ILC) can cause high temperatures
and localised coagulative necrosis whilst preserving the prostatic urethral
lumen which it is hoped, but not yet proven, may reduce postoperative dysuria
following treatment. Since there is no generally agreed system for quantifying
post laser symptoms it is difficult to compare one method with another in any
meaningful way.
Laser energy can be introduced into prostatic tissue either by:
1. A simple bare fibre which is cheap, but may break.
2. A bare fibre within a cannula through which saline flows to protect the cannula
and the fibre. Ultrasound (US) visible changes during prostatic heating allows
control of the heating process and follow up of response. In our study of 36
men pre-operative AUA-7 scores of 22 (18 -29) fell to 7.6 (0 - 25 ) and peak
flow rates increased from 9.5 (4-14 ) to 14.5 mls/sec (7-32) at 6 months. Patients
were taught intermittent clean self catheterisation (ICSC) for an average of
3.7 days (0- 7). Clearly, however, not all men benefitted with 4 clearly failing
to respond and another 4 responding only moderately. Of those with a good response
the average SS change was 17 (8-28), with an average Qmax change of 6.6 mls/second
(2-17).44
3. A more complex fibre with a distal “diffusor tip” attached. Over
350 men have been treated by the Munich group since July 1991, by a series of
protocols making comparison difficult. Muschter and Hofstetter described the
results of several diffusor tip fibres in 239 men treated by the transperineal
(n=75) or the transurethral interstitial approach. Twelve month follow up data
was available on 127 men. AUA symptom scores (SS) fell from 25 to 6, peak flow
rates rose from 8 to 18 mls/sec at 12 months. Irritative symptoms were noted
in 12.6%, 4% developed urethral strictures, 7% retrograde ejaculation and no
previously potent man developed impotence45.
Preliminary (promotional) data reported for the Indigo diffusor tip fibre and
830 nm diode laser (Indigo, Palo Alto, California, USA) was in line with ILC
results outside the German experience. Multicentre RCTs comparing the Indigo
diffusor tip fibre and 830 nm diode laser to TURP are underway. One small study
has been reported of 25 men treated with this laser and fiber system46. Results
included mean SS improvement from 20.6 to 9.4 at 1 month and 6.9 at 3 months.
Peak flow rate (Q max) increased from 9.1 to 14.1 and then to 20.3 mls/sec.
The system senses temperatures at the fiber tip and adjusts power output with
the intention of maintaining a temperature of 100 0C (2120F) throughout the
treatment cycle. Temperatures reached and power levels required varied according
to the site of puncture with apically placed lesions requiring less energy to
achieve and maintain target temperature. Presumably the heat losing mechanisms
are less effective at the prostatic apex. Since this report the laser source
and system has been “enhanced” so we await new data from studies of
the new system before we can really define the effectiveness of the “Indigo”
method of ILC.
4) Transurethral endoscopic fibre with various beam deflecting devices. Initially
the most popular methods of laser BPH treatment utilised a miniature reflector
or prism at the end of the “side-firing” fibre to perform either coagulation
(“visual laser ablation” VLAP) or vaporisation (TUVP) of the prostate.
Many operators also coagulated or cut the bladder neck mechanism in order to
reduce catheter duration but probably also increasing the incidence of retrograde
ejaculation.
Method of laser coagulation (modified visual laser ablation of the prostate
or VLAP)
Narayan47 describes a method modified from descriptions of visual laser
ablation by Costello48 and Kabalin49. The modified technique consisted of laser
energy application at 60 watts for 60 seconds to 11 to 19 spots depending on
the size of the prostate. The spots included the 5 and 7 o'clock positions at
the bladder neck, the 6 o'clock position for the median lobe, and the 5, 7,
11 and 1 o'clock positions for each 1 cm. length of prostate. For a 3 cm. length
of prostate this resulted in 11 spot applications (3 at the bladder neck, and
4 each at the mid and apical prostate areas), while 4 additional spots were
used for each additional 1 cm. length. Each spot was wide and covered a 1 cm.
area. To ensure coagulation and avoid evaporation, the spot size was enlarged
by holding the fiber 2 to 4 mm. away from the tissue. The technique resulted
in coagulation of the entire prostatic urethra as visualized by absence of pink
mucosa.
Kabalin reported a small prospective RCT where improvements in flow rates and
symptom scores in 13 men that equalled a TURP arm and were durable over 18 months
followup 50. Larger prospective, multicentre RCTs comparing Nd:YAG VLAP to standard
TURP became available and gave more reliable indications of early efficacy even
though they were industry sponsored. Table 1 shows SS and Qmax results. A U.S.
based study51 enrolled 115 men into 2 trial arms (VLAP by Urolase at 40W, 60
sec, and TURP). The authors concluded VLAP was less effective than TURP but
was associated with less “serious” complications (10.7% versus 35.6%)
and claimed “non-serious” complications were equal - but only when
the higher rate of post VLAP retention and recatheterisation (30.4% vs 8.5%)
was excluded.
In a British Urolase study 52 5 centres enrolled 151 men into the 2 trial arms
. A similar "spot coagulating"; technique was used but using a higher power
(60W power for 60 s). VLAP was associated with significantly less haemorrhage
and transfusion and a shorter inpatient stay than TURP (2.7 days vs 4.3) but
a longer catheter time (4.8 days vs 2.7). Post operative dysuria was higher
at 4 weeks for VLAP (41% versus 15%) and persisted in 15% of men to 3 months
compared to only 1% in the TURP group. All remained potent who were so before
treatment but there was a surprisingly high incidence of retrograde ejaculation
in the VLAP group (33%, compared to 63% for TURP).
At endoscopy at 6 months approximately 40% had residual tissue present , probably
due to prudent operators leaving an adequate safety margin at the prostatic
apex to avoid stricturing or sphincteric damage. Clearly this untreated tissue
may impact on long term outcomes.
These studies revealed encouraging early results and the expected problems of
the coagulation method when performed in a variety of centres that probably
represented the “real world”. Obviously much longer follow up is needed
to show whether these results are durable and the method cost effective. Unfortunately
longer term outcomes from these studies have not been reported though presumably
the data might still be available. An opportunity to provide the longer term
data that we need for the coagulating method may havebeen lost.
The world moves on and even before the results of coagulation methods were clear
few urologists were doing the procedure in its simple coagulating form. There
was a rapid trend towards using higher energy doses, higher power, higher PD
and “vaporising” methods53 in an effort to achieve an immediate tissue
defect within the prostatic fossa. In practice the endoscopically obvious “vaporisation”
is accompanied by a degree of underlying coagulation as well.
Method of laser vaporisation (TUVP) 47
Before laser evaporation of the prostate standard cystourethroscopy is
performed. The limits of laser ablation at the bladder neck and the verumontanum
are marked in 4 quadrants at the 8, 4, 11 and 1 o'clock positions. The marks
are made 0.5 cm. below the bladder neck and 0.5 cm. proximal to the most prominent
portion of the verumontanum.
In all patients initially the laser is applied at the 5 and 7 o'clock positions
on the bladder neck at 60 watts until circular fibers of bladder neck are visible.
The median lobe enlargement is treated next by laser therapy at a 45-degree
angle to the lobe from the right to left sides and vice versa. The ablation
is completed by laser application at the 6 o'clock position deep enough to visualize
the bladder neck. The laser is used until evaporation of all median lobe tissue
is achieved as suggested by the appearance of bladder neck muscle fibers and
a smooth, flat bladder neck between the 5 and 7 o'clock positions.
Prostate evaporation is then performed. Four furrows are made from the bladder
neck to the verumontanum using the previously delineated landmarks. The furrows
at the 8 and 4 o'clock positions are made initially by dragging the fiber on
tissue. Tissue evaporation is achieved by holding the laser fiber in contact
with the area to be treated and by dragging it at a rate of 1 cm. for every
20 to 30 seconds of laser energy delivery. At the beginning of each furrow dragging
is commenced once bubbling is noted signifying evaporation of tissue. Dragging
the fiber at a rate of 1 cm./20 to 30 seconds at 60 watts results in a furrow
5 to 7 mm. deep with a 3 to 4 mm. rim of coagulated tissue immediately next
to it. After completion of the 4 furrows, a second or third pass is made at
the 5 and 7 o'clock positions to determine the depth of the prostate so as to
judge the extent of evaporation necessary to obtain satisfactory results. By
visualizing the prostatic capsule at some point along the length of the furrow
in the lateral lobe (which has the maximal depth), the adequacy of evaporation
necessary can be confirmed.
To complete the procedure and establish an open channel, tissues between the
furrows (that is between the 11 and 7 o'clock, and the 1 and 5 o'clock positions)
are evaporated in a similar manner. The fiber is dragged faster in charred areas
(10 seconds per cm.) and slower in coagulated areas (35 to 45 seconds per cm.)
because of differences in heat absorption by charred (rapid) versus blanched
(slow) tissues. The fiber is also moved at a faster rate (10 seconds per cm.)
towards the apex of the prostate where there is less depth to the prostatic
lobes.
The procedure is complete when, by visual inspection, a large channel (similar
to that after standard transurethral electroresection of the prostate) is created
and digital rectal palpation indicates that there is no excessive residual prostate
tissue. Any excessive tissue palpated between the cystoscope and rectal finger
is evaporated by repeat laser application. The laser is applied to tissue on
the floor of the prostate (between the 5 and 7 o'clock positions) only at the
median lobe and on either side of the verumontanum. The rest of the tissue is
not obstructive and, therefore, laser delivery is avoided, which also probably
avoids any inadvertent rectal injury. Hemostasis is achieved by either use of
the laser at a lower power setting (20 to 40 watts) and/or moving the fiber
away from tissue contact by 2 to 3 mm. A 20F Foley catheter is left indwelling
at the end of the procedure in all patients.
Narayan et al. found, in an RCT randomising 64 men between a very high energy
vaporising method and a more traditional coagulating technique that though both
were effective (Table 1) there was a statistically significantly better flow
rate improvement following vaporisation. Coagulated patients were 4 times more
likely to develop prolonged postoperative urinary retention (defined as >7
days) and had higher reoperation rates (16% vs 0%)47.
Further data on transurethral laser evaporation of the prostate from the same
group includes the results in 168 men with up to 12 months of followup. In fact,
of the 168 men reaching 6 months only 129 (76.8%) had reached 12 months of follow
up at the time of reporting. Mean age was 68.2 (48-92) and prostatic volume
60.1 (16-132)mls. 37 had a catheter in situ and they usually had major comorbidity.
Pre treatment AUASS of 20.6 fell 13.4 (or 65%) to 7.2 (4.1 for the retention
group). Pre treatment Qmax of 8.2mls/sec. increased 10mls/sec (or 122%) to 18.2mls/sec.
(16.4 for the retention group). 78% had 50% or more improvement in Qmax, 78%
had 50% or more improvement in SS. 71% had had 50% or more improvement in both
Qmax and SS. Mean energy given was high at 131,281J, or 2,281.7J/cc. of measured
prostatic tissue. They used 1.28 fibers per case and men stayed 3.2 days in
hospital with a mean catheter duration of 3.4 days. 5 (3%) failed and underwent
TURP. 5(3%) voided after a period of delay so were catheterised for 6.8days
(5-21d). This group reported irritative symptoms in the 1st month in 32 men
(22.6%) for a mean of 22.7days. 1 man developed a stricture during the period
of follow up. They concluded that laser evaporation of the prostate was safe
and effective but recognised the remaining problems with irritability, suggesting
"These symptoms are crippling" and were the main reason patients chose
TUEVP or TUNA as an alternative to laser treatment. Multiple fibres were used
which added to cost and they reported that laser vaporisation took longer than
TURP for a comparable gland ("25-50% longer").
Gilling et al 38, using the Holmium laser in side firing mode, described successful
early removal of catheters and very good overall results with this “vaporising”
wavelength which can be used either alone or in conjunction with the Nd-YAG
laser.
This method was rapidly replaced by purely Holmium vaporisation of the prostate39
with further good results. Despite thes e results this New Zealand group subsequently
abandoned coagulative or vaporising methods and further developed Holmium techniques
for directly incising and mobilising the prostatic lobes in a manner similar
to resection with results exceeding their TURP outcomes41 (see above).
Discussion
Variability in methods and results is to be expected since we still do
not know the answers to many basic questions. We do not even know how much tissue
we have to destroy to guarantee a good, long term result though it is probably
less than we thought and laser techniques have been shown by pressure flow studies
to overcome obstruction despite relatively modest tissue removal compared to
a TURP 54-56.
Endoscopic laser prostatectomy by these different methods appears safe. It is
usually quicker if one avoids big prostates(>50-60gms). Rapid “barbecueing"
or charring of the adenoma surface should be avoided as it leads to high surface
temperatures and effects but less deep penetration of light.
Whether size of the prostate is an important consideration is unclear. Jung
et al57 reported that VLAP and TURP led to similar symptomatic responses but
that VLAP only lowered the “obstructive grade” (measured by pressure
flow studies) in those men with prostate size below 50mls whereas TURP was effective
for all prostate sizes. Narayan et al. reported that size did not impact on
the success of the vaporising method (TUVP) in their experience58.
Similarly, men presenting with acute urinary retention seem to do as well as
purely symptomatic men following VLAP59 or TUVP60.
A period of obstruction and “irritability” is common, especially after
coagulating laser methods (but can follow any heat therapy). Magnetic resonance(MR)
studies immediately following VLAP have shown a mean increase in the volume
of the prostate of 34%61,62 which probably contributes largely to the obstruction.
It is still not clear to what degree various factors are to blame (such as residual
obstruction, infection, the presence of a suprapubic or urethral catheter).
ICSC and temporary stents, either absorbable63 or plastic, have been used as
alternatives to catheterisation for post laser obstruction. Petas et al. 64
compared the use of a biodegradeable poly-dl-lactic acid (SR-PLA) spiral stent
and suprapubic catheter (n=22) to a suprapubic catheter (SPC, n=23) alone following
VLAP. Generally voiding was reestablished earlier in those using the stent and
SPC so the SPC could be removed earlier. Voiding started on the 1st or 2nd day
after VLAP in 18 of 22 with a stent (plus SPC) and in 8 of 23 with the SPC alone.
Outcomes (Qmax, SS) were similar at 6 months but the urinary tract infection
rate increased with the duration of SP catheterisation. However, stent degradation
was prolonged and led to stone formation in 2 men. Clearly, if improved stents
prove effective and acceptable to patients then the simpler coagulative method
might once again become the leading technique.
Early reports tend to come from enthusiasts and are usually encouraging. Whether
this remains true when performed in more routine and widespread urological practice
is not yet known. These techniques are more popular in some countries than others
and were minimally taken up in general urological practice in the U.K. for instance.
Laser methods are reported to be almost equivalent to TURP in terms of symptom
response42,51,52. One is led to expect an increase in flow rates of approximately
50% (compared to 100% following a TURP) in an unselected UK population52. Results
expressed as means and averages can be misleading and current studies would
be more helpful if results were also expressed in terms of generally agreed
categories i.e. what proportion obtain an "excellent", "good", "moderate" or
"poor" result - if we could agree such categories: such a standardisation is
underway but not yet complete 65. McCullough has suggested studies should report
the proportion of subjects achieving 50% or greater improvement in Qmax and
/ or symptoms66.
Kabalin found VLAP a cheaper treatment option67 though Dixon and Lepor, in the
first prospective, double blind, laser RCT comparing the safety, efficacy and
cost 68, found VLAP no cheaper than TURP in their institution. The Oxford laser
RCT found TURP to be more cost effective than contact tip laser methods, mainly
due to the cost of consumables69. But if fibers are carefully used more than
once70 and if competition among fiber producers intensified then this cost could
fall substantially.
Conclusions
Despite some excellent reports laser prostatectomy methods in general use
do not yet seem as predictably effective in increasing flow rates as TURP though
the symptomatic improvement is nearly as good. But the procedures cause little
bleeding, are less taxing for the patient, and can be day case procedures -
which are considerable advantages. The side firing coagulation method is best
known and simplest to use but gives delayed results. New stents might improve
outcomes. Data on vaporising methods are now available and are more impressive,
leading McCullough to comment that "The vaporization technique has many
advantages. Efficacy appears equivalent or nearly equivalent to that of standard
transurethral resection of the prostate. An instant channel is created, no bleeding
occurs, no absorption of fluid is noted, it can be used on ill patients, including
those anticoagulated with heparin, coumadin, nonsteroidal anti-inflammatory
drugs and aspirin, no tissue is obtained, no pathology report expense is generated
and no postoperative irrigation is required. It deserves wider use"66.
Bare fiber Holmium methods of prostatic resection appear to approach the “gold
standard” or “yardstick” of TURP but more and longer term data
from more centres is needed (and this applies to most of the methods described).
The case for contact tip methods has been greatly improved but more long term
studies are needed and the cost issue may be crucial. Interstitial methods may
well have a role in older, sicker men with larger prostates. ILC remains interesting
but unfulfilled due to the lack of good prospective, randomised studies and
partly because the technique is still in evolution - which is true of all methods
of laser prostatectomy. We need to determine the longevity of the initial response
to laser treatment and the incidence of retreatment over many years. Only when
we have this data will we be able to define the role of “laser prostatectomy”.
The fundamental challenge to laser techniques is from the “new” TURP,
rejuvenated by new vaporising roller or loop technology and improved generator
design. The challenge of the laser methods has led to a re-appraisal of what
we need to do to relieve symptoms and obstruction in the most cost effective
and “patient friendly” manner with the result that significant advances
in electrosurgical techniques have ocurred. The explosion of treatment options
should not be regarded as a threat but as a development that reinforces the
primary role of the urologist as the only health care professional equipped
to guide the symptomatic or obstructed man to the best treatment option for
him to undergo.
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