Cryoablation of the Prostate: Technical Recommendations
Cryoablation of the Prostate: Technical Recommendations
The European Association of Urology guidelines on prostate cancer state that cryotherapy is a true therapeutic alternative for patients with clinically localized prostate cancer. The aim of this paper is to establish a uniform practice for performing prostate cryoablation. A collaboration has been set up among five European centres with experience in almost 1000 prostate cancer patients on the use of cryotherapy. The present recommendations were developed through sharing of experience and thorough discussions within the group. This first paper from the group establishes the technical recommendations for use of prostate cryotherapy.
Cryotherapy has been performed in Europe for over 50 years. The European Association of Urology guidelines on prostate cancer state that cryotherapy is a true therapeutic alternative for patients with clinically localized prostate cancer. The American Association of Urology recently made an announcement of a best practice statement confirming cryotherapy as a valid treatment option for both primary and recurrent localized prostate cancer. In 2005 in the UK, the National Institute of Clinical Excellence approved the use of cryotherapy for patients with prostate cancer, both as a primary treatment and as salvage treatment after radiotherapy or hormone therapy. National Institute of Clinical Excellence clinical guidelines on prostate cancer released in February 2008 reversed this decision suggesting that the treatment should be used in the setting of clinical trials. Ongoing debate has resulted in a further revision to allow UK physicians to collect data on patients treated locally for funding requirements.
Cryotherapy causes cell death through two principle mechanisms. First, as the temperature falls, extracellular ice crystallizes causing movement of water from the intracellular to the extracellular environment after an osmotic gradient. As the temperature continues to fall, intracellular ice crystals form, causing direct damage to the intracellular organelle system and the cell membrane. The second mechanism is platelet aggregation and microthrombus formation in small blood vessels, which leads to ischaemic change in the tissue area supplied by the affected blood vessels. These changes lead to coagulative necrosis and cause a well demarcated lesion as can be seen in Figure 1. In addition, severe temperature changes and ischaemic change induce apoptosis in cells at the periphery of the cryolesion. The effectiveness of the cellular destruction depends on rapid freezing, the lowest temperature reached and slow thawing. This is generally achieved through two freeze–thaw cycles to a target temperature of −40°C.
(Enlarge Image)
Figure 1.
Cryotherapy lesion in myocardial tissue lesion is well demarcated with complete fibrosis of the tissue. Images kindly supplied by Dr J Baust.
Cryoablation of prostate cancer first took place in 1968 using probes cooled by liquid nitrogen in a closed system. The early technique was associated with considerable complications, such as rectorurethral fistulas, urethral sloughing and urinary incontinence. With the introduction of transrectal ultrasound (TRUS) guidance and the urethral warming catheter, improved results were achieved. The subsequent development of third generation cryotherapy using ultra-thin 17-gauge needles with echogenic tips has allowed highly controlled and accurate delivery of the treatment. The current system uses high pressure argon and helium gas for freezing and warming, respectively. The temperature change is governed by the Joule–Thompson effect, whereby high pressure gases, when forced though a very small opening into a low pressure area (within the tip of the CryoNeedle), undergo specific temperature changes. This allows the freezing and subsequent thawing of the prostate using the same needle. During the treatment, the temperature in different areas of the prostate is monitored in real time by means of interstitial thermosensors. The 17-gauge needles are placed under TRUS guidance through the skin of the perineum using a brachytherapy-like template without the need for tract dilatation and with minimal trauma to the patient. As the gas is delivered through the specialized needles, it cools the prostate tissue rapidly to the target temperature of –40°C. The ice ball is clearly visible on TRUS as it forms and is monitored continuously throughout the procedure. The use of urethral warmer reduces the incidence of urethral sloughing.
A collaboration has been enacted among five European centres with experience in almost 1000 prostate cancer patients treated with cryotherapy. The procedure described here relates to the SeedNet equipment (Galil Inc.). The aims of the group are to establish a uniform practice for performing prostate cryoablation and to develop a prospective European database on long-term outcomes with this therapy. This first paper from the group reports on the second meeting of the group establishing the technical recommendations for prostate cryotherapy; subsequent publications will detail outcomes, including efficacy and safety.
Abstract and Introduction
Abstract
The European Association of Urology guidelines on prostate cancer state that cryotherapy is a true therapeutic alternative for patients with clinically localized prostate cancer. The aim of this paper is to establish a uniform practice for performing prostate cryoablation. A collaboration has been set up among five European centres with experience in almost 1000 prostate cancer patients on the use of cryotherapy. The present recommendations were developed through sharing of experience and thorough discussions within the group. This first paper from the group establishes the technical recommendations for use of prostate cryotherapy.
Introduction
Cryotherapy has been performed in Europe for over 50 years. The European Association of Urology guidelines on prostate cancer state that cryotherapy is a true therapeutic alternative for patients with clinically localized prostate cancer. The American Association of Urology recently made an announcement of a best practice statement confirming cryotherapy as a valid treatment option for both primary and recurrent localized prostate cancer. In 2005 in the UK, the National Institute of Clinical Excellence approved the use of cryotherapy for patients with prostate cancer, both as a primary treatment and as salvage treatment after radiotherapy or hormone therapy. National Institute of Clinical Excellence clinical guidelines on prostate cancer released in February 2008 reversed this decision suggesting that the treatment should be used in the setting of clinical trials. Ongoing debate has resulted in a further revision to allow UK physicians to collect data on patients treated locally for funding requirements.
Cryotherapy causes cell death through two principle mechanisms. First, as the temperature falls, extracellular ice crystallizes causing movement of water from the intracellular to the extracellular environment after an osmotic gradient. As the temperature continues to fall, intracellular ice crystals form, causing direct damage to the intracellular organelle system and the cell membrane. The second mechanism is platelet aggregation and microthrombus formation in small blood vessels, which leads to ischaemic change in the tissue area supplied by the affected blood vessels. These changes lead to coagulative necrosis and cause a well demarcated lesion as can be seen in Figure 1. In addition, severe temperature changes and ischaemic change induce apoptosis in cells at the periphery of the cryolesion. The effectiveness of the cellular destruction depends on rapid freezing, the lowest temperature reached and slow thawing. This is generally achieved through two freeze–thaw cycles to a target temperature of −40°C.
(Enlarge Image)
Figure 1.
Cryotherapy lesion in myocardial tissue lesion is well demarcated with complete fibrosis of the tissue. Images kindly supplied by Dr J Baust.
Cryoablation of prostate cancer first took place in 1968 using probes cooled by liquid nitrogen in a closed system. The early technique was associated with considerable complications, such as rectorurethral fistulas, urethral sloughing and urinary incontinence. With the introduction of transrectal ultrasound (TRUS) guidance and the urethral warming catheter, improved results were achieved. The subsequent development of third generation cryotherapy using ultra-thin 17-gauge needles with echogenic tips has allowed highly controlled and accurate delivery of the treatment. The current system uses high pressure argon and helium gas for freezing and warming, respectively. The temperature change is governed by the Joule–Thompson effect, whereby high pressure gases, when forced though a very small opening into a low pressure area (within the tip of the CryoNeedle), undergo specific temperature changes. This allows the freezing and subsequent thawing of the prostate using the same needle. During the treatment, the temperature in different areas of the prostate is monitored in real time by means of interstitial thermosensors. The 17-gauge needles are placed under TRUS guidance through the skin of the perineum using a brachytherapy-like template without the need for tract dilatation and with minimal trauma to the patient. As the gas is delivered through the specialized needles, it cools the prostate tissue rapidly to the target temperature of –40°C. The ice ball is clearly visible on TRUS as it forms and is monitored continuously throughout the procedure. The use of urethral warmer reduces the incidence of urethral sloughing.
A collaboration has been enacted among five European centres with experience in almost 1000 prostate cancer patients treated with cryotherapy. The procedure described here relates to the SeedNet equipment (Galil Inc.). The aims of the group are to establish a uniform practice for performing prostate cryoablation and to develop a prospective European database on long-term outcomes with this therapy. This first paper from the group reports on the second meeting of the group establishing the technical recommendations for prostate cryotherapy; subsequent publications will detail outcomes, including efficacy and safety.
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