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4-2 Cryosurgery for Prostate Cancer

Franco Lugnani,Lizhi Niu,Liang Zhou,Kecheng Xu

ABSTRACT

  1. As primary treatment,cryosurgery is suited for patients with low-risk tumor features (ie, serum prostate-specific antigen [PSA] level <10 ng/ml, diagnostic biopsy Gleason score <6, clinical stage T1c or T2a) . Cryoablation has also been used for local disease control in patients with known metastatic disease on systemic therapy who require palliative maneuvers for local symptoms
  2. As salvage treatment, cryosurgery has been established as a viable alternative for patients in whom radiotherapy has failed. Candidates for such salvage treatment should be patients with high-risk features, such as a preradiation PSA level of more than 20 ng/mL, Gleason score of 8-10, or a rapidly rising PSA level after radiation

INTRODUCTION
Prostate cancer is found mainly in older men. About 90% of new cases of prostate cancer are caught early, and almost 100% of men with these early cancers survive 5 years or more after being diagnosed[1].
Different types of treatment are available for patients with prostate cancer, including watchful waiting, operation, radiation and hormone therapy[2,3].

Cryosurgery is a treatment that uses an instrument to freeze and destroy prostate cancer cells. During the past years, the therapy has been paid a great attention, become an important alternative modality for localized and recurrent prostate cancer[4-6].
INDICATION
As primary treatment,cryosurgery is suited for patients with low-risk tumor features (ie, serum prostate-specific antigen [PSA] level <10 ng/mL, diagnostic biopsy Gleason score <6, clinical stage T1c or T2a) . Cryoablation has also been used for local disease control in patients with known metastatic disease on systemic therapy who require palliative maneuvers for local symptoms[7].
As salvage treatment, cryosurgery has been established as a viable alternative for patients in whom radiotherapy has failed. Candidates for such salvage treatment should be patients with high-risk features, such as a preradiation PSA level of more than 20 ng/ml, Gleason score of 8-10, or a rapidly rising PSA level after radiation[8].
Relative contraindications include the following:

  1. Prior transurethral resection of the prostate with a large tissue defect.
  2. Significant symptoms of urinary obstruction prior to treatment.
  3. Large prostate size: Even with multiple probes, complete ablation of glands larger than 50 cm3 is difficult, and multiple probe insertions and prolonged freezing times may be required. In these cases, the prostate may be cytoreduced with neoadjuvant hormonal ablation before cryoablation.
  4. History of abdominoperineal resection for rectal cancer, rectal stenosis, or other major rectal pathology.

TECHNIQUE
Use of Cryocare System, Endocare, Inc., Irvine, CA
Usually, 6 cryoprobes are used which, except for large (>35 cm3) or small glands, allow sufficient but not excessive freezing of the gland. There are 4 guidelines for cryoprobe placement, as follows: (1) cryoprobes should not be placed >1.8 cm apart, (2) cryoprobes should not be placed >1.0 cm from the margin of the prostate, (3) the distance between the urethra and any cryoprobe should not be >0.8 cm, and (4) the posterior cryoprobes should be placed such that their separation is less than twice the distance to the posterior capsule of the prostate (Figure 4-2-1)[7].


Figure 4-2-1. Placement of cryoprobes into prostate.TRUS probe, thermosensor and urethral warmer are showed

Because of sonographic shadowing beyond the proximal ice ball edges, the cryoprobes are operated from anterior to posterior. Cryoprobes are not inserted directly. Rather, a simple dilator system (FastTrac, Endocare, Inc.) is used to insert a sheath into which a probe is placed once all sheaths have been inserted into the gland.
Thermosensor placement takes place after all the sheaths have been placed but before the warming device is inserted into the urethra and before the cryoprobes are inserted into the sheaths. There are 5 thermosensors that are placed, 3 of which ensure that adequately cold temperatures have been reached within the prostate and 2 of which ensure that collateral freezing does not occur in the sensitive anatomy adjacent to the prostate. To ensure that sufficiently cold temperatures have been reached, thermosensor is placed in each neurovascular bundle and is placed at the apex of the gland. Prophylactic thermosensors are placed in the external sphincter and just anterior to the rectal wall at Denonvilliers fascia.
Goals during the procedure are to achieve temperatures as follows: (1) at least as cold as -40°C in the neurovascular bundles, (2) not colder than -15°C at the external sphincter, (3) not colder than -40°C at Denonvilliers fascia when the thermosensor is placed at the posterior prostatic capsule, and (4) not colder than 0°C at Denonvilliers fascia when the thermosensor is placed at the anterior rectal wall.
Once all cryoprobes are placed, the freezing process is started with the anterior probes, with 50% of argon gas flow. This continues until the anterior ice balls begin to merge. After 2 to 5 minutes of anterior ice formation, the posterolateral cryoprobes are activated at 50% to 70%. Operation of these probes shuts off the blood supply to the prostate. Once adequate thermosensor temperatures are reached at the neurovascular bundles, probes 5 and 6 are activated at 25% to 50% argon gas flow. At this stage of the freeze cycle, the ice ball at the posterior of the prostate needs to be intently monitored to ensure adequate freezing of the gland and protection against freezing of the rectal wall. This is accomplished with the combined use of sonographic visualization and careful monitoring of the thermosensor located in Denonvilliers fascia. Although the incidence of rectourethral fistula formation is extremely rare in modern cryoablation practice, such watchful vigilance serves as insurance against the occurrence of rectal injury.
There are 2 criteria that are relied on to determine the completeness of the freeze cycle, which usually lasts about 10 minutes: (1) the targeted lethal temperature (typically -40°C) reading in the thermosensors positioned in the neurovascular bundles and at the apex of the gland, and (2) extension of sonographic freezing to outside the gland in all visible dimensions without injury to the rectal mucosa.It must be noted that both these criteria must be met; either on its own is insufficient. Temperature monitoring is necessary as ultrasound is unable to image temperature and can, in fact, overestimate the size of the ice ball because of refraction. Sonographic confirmation that the ice ball has enclosed the entire posterior margin of the prostate and has not intruded into the rectal mucosa is imperative.
Once the freeze is complete, probes are switched to the thaw mode, which circulates helium gas through the probes and results in an increase in temperature at the cryoprobe tip (active thaw). Once cryoprobe temperatures are above freezing, the flow of helium gas is stopped, and the remaining ice ball is allowed to thaw by the warmth of the body (passive thaw). When the prostate is completely thawed, the second freeze-thaw cycle is initiated in the same manner as the first.
After the second freeze-thaw cycle, the cryoprobes and thermocouples are thawed and removed, insertion sites are sutured, and the urethral warmer is removed before transport to the postanesthesia care unit.
Use of cryosurgical system, Galil Medical, Yokneam, Israel
Seventeen-gauge cryoprobes are directly inserted transperineally through a brachytherapy template under TRUS guidance. One to five probes form a controllable group. Up to six groups may be used at the same time. Each group is used to cover a different anterior-posterior level(Figure 4-2-2)[9].
A multifrequency biplanar TRUS probe is attached into the holding device adapting cradle. The prostate is imaged and its dimensions measured. Probes are inserted into the desired loci identified by the coordinates on the aiming grid projected on the prostate TRUS image. Up to 30 simultaneously active probes in six distinct groups may be used. Cryoprobes are inserted in 3-4 horizontal layers 1 cm apart. Each layer groups 2 to 5 probes according to the prostate width.
The lethal -20°C isotherm is located at a radius of 7 mm and 10 mm, respectively. Since the iceballs progress longitudinally 5 mm past the probe tip, the probes are advanced into the prostate base and positioned 5mmcaudal to the bladder neck. The most posterior layer is ideally located 5 to 7 mm anterior to the prostate capsule. Given the propensity of prostate cancer to expand through the capsule in locations pierced by the neurovascular branches, lateral probes is placed to permit extraprostatic freezing and facilitate killing by early shut down of the arterial supply to the gland.The prostatic urethra is identified by TRUS in both the longitudinal and the transverse views, and the cryoprobes are placed 8 to 9 mm away from the urethra.
To maintain TRUS visibility, the freezing is started at the anterior probe layer and continued posteriorly. Uncovered areas may be visualized and a correcting maneuver may be used. Two freezing cycles are performed. Between the cycles, the prostate may be allowed to thaw passively (15 to 20 minutes) or actively ( 7 to 8 minutes) using helium.


A

B

Figure 4-2-2. A.SeedNet 17-gauge argon/helium-driven probe with a sharp tip capable of developing (A) a 27-mm-long and 18-mm-wide teardrop-shaped iceball that expands 5 mm past the tip after 5 minutes of continuous freezing and 32 mm long and 26 mm wide after 10 minutes, respectively. (B) Placing probes 1 cm distant from each other through a brachytherapy template (C) enables sufficient overlap between probes to create a confluent icy mass (D).B.Sagittal representation of patient position and cryoprobe placement. Patient positioning, TRUS probe-holding device (H), and template are shown in the inset at the upper right.
From Zisman Aet al.Urology 2001;58:988-993

CLINICAL DATA
Primary treatment
Cryosurgery, as a primary treatment of prostate cancer, has a different results[10-14]. The efficacy is mainly estimated with local residue tumor and PSA levels. There were a total of 3047 cases with cryosurgery in 17 reports, 14 of which were followed-up for median 6 months with range of 3 months to 5.4 years. The local residue tumor was seen in 8% -25% with mean of 17.4%, the biochemical disease-free survival (bDFS) 14%-96% with mean of 52.4%(Table 4-2-1). It seems that along with gather experience, the efficacy is increased.
Table 4-2-1. The results of cryosurgery for prostate cancer


Reporters

Cases

Residue tumor(%)

Follow-up
(Mos)

bDFS
criteria

bDFS(%)

Onik[15], 1993

23

17

3


. . .


. . .

Miller[16], 1994

62

21

3


. . .


. . .

Bahn[17], 1995

130

8

. . .


. . .


. . .

Coogan[18], 1995

87

17

12

<0.2 ng/mL

33

Wieder[19], 1995

61

13

3

<0.5 ng/mL

57

Bales[20], 1995

23

14

1 2

<0.3 ng/mL

14

Shinohara[21], 1996

102

23

3

<0.1 ng/mL

48

Wake[22], 1996

63

25

3

<0.1 ng/mL

25

Cohen[23], 1996

383

18

2 4

<0.4 ng/mL

55

Pisters[24], 1997

150

18


. . .

<0.2 ng/mL

46

Lee[25], 1999

81

3


. . .


. . .


. . .

Gould[26], 1999

27


. . .

6

<0.2 ng/mL

96

Long[27], 2001

975

18

24

<0.5 ng/mL

60 (Low-risk), 45 (Mid-risk), 36 (High-risk)

Bahn[28], 2002

590

13

65

<0.5 ng/mL

61 (Low-risk), 68 (Mid-risk), 61 (High-risk)

Han[29], 2003

106

. . .

1 2

<0.4 ng/mL

75 (78 Low-risk, 71 High-risk)

Lam[30], 2005

27

. . .

6

<0.4 ng/mL

90

Katz[31] 2005

157

. . .

37

<0.4 ng/mL

73.3

bDFSbiochemical disease-free survival

Local control
Among patients undergoing rebiopsy 3-24 months after treatment with a standard 5-probe cryosurgery system, 7.7%-25% have been found to have residual malignant glands, and 42%-71% have been found to have focal areas of viable benign epithelium. A number of disease- and treatment-related factors have been shown to predict rates of local control. In one series, for example, the likelihood of positive biopsy findings was 9% for subjects with clinical stage T1 or T2 disease compared with 21% for those with T3 disease. Persistent or recurrent cancer is more likely among tumors located in the prostatic apex or seminal vesicles compared with those located in the mid gland or base[28,32,33].
A 2001 pooled analysis stratified patients into the following risk groups[27]: (1) low-risk patients had a PSA level less than or equal to 10 ng/ml, Gleason score less than or equal to 6, and clinical stage T1 or T2a disease; (2) intermediate-risk patients had a PSA level more than 10 ng/ml, Gleason score equal to or more than 7, or clinical stage T2b disease or higher; and (3) high-risk patients had 2 or 3 of these adverse risk factors. The distribution of patients among the risk groups was 25%, 34%, and 41%, respectively. The positive biopsy rate in the series was 18% overall: 12% among low- and intermediate-risk patients and 24% among high-risk patients.
The use of 2 freeze-thaw cycles rather than 1 reduced the positive biopsy rate from 64% to 11% in a series of primary cryosurgery patients and from 29% to 9% among a group treated with salvage cryosurgery for radiation failure. Other technical advances have also produced improvements[21,24]. One series reported a reduction of the positive biopsy rate from 83% to 10% as a result of introducing the use of thermosensors during treatment; another series reported a positive biopsy rate of only 2.5% by using 6-8 cryosurgery probes rather than the conventional 5 probes[25,36].
Biochemical failure
Initially, PSA levels following cryosurgery rise sharply and then fall, reaching a nadir within 3 months after treatment in most patients. Because this treatment modality does not ablate every gland in the prostate at the microscopic level, a persistently detectable PSA level following cryosurgery may not indicate persistent disease. The target nadir has not been established with as great a degree of certainty as that following surgery, but a clear correlation exists between the nadir achieved initially and the eventual disease progression. Biochemical failure, defined as a rise in PSA level of 0.2 ng/ml after a nadir of less than 0.5 ng/ml, was reported to be lowest in subjects whose PSA nadirs were less than 0.1 ng/ml[35].
In a pooled analysis with a median follow-up of 24 months, actuarial 5-year biochemical disease-free survival (bDFS) rates were 60%, 45%, and 36% for low-, intermediate-, and high-risk patients based on a PSA threshold of 0.5 ng/ml to define failure; rates were 76%, 71%, and 45% using a threshold of 1 ng/ml (Long, 2001). A report of cryosurgery experiences in a community setting indicated that 84% of the patients reached a PSA nadir of less than 0.4 ng/ml, although the follow-up period was quite short[7]. Prepelica[37] recently reported a series of 65 men with high-risk prostate cancer, defined as PSA > 10 ng/ml and/or Gleason score > 8. They found an 83.3% bDFS rate based on the American Society for Therapeutic Radiology and Oncology (ASTRO) definition at median 35-month follow-up. Fifty percent of patients achieved a nadir PSA <4 ng/ml, and 35% achieved a nadir of <1 ng/ml. The morbidity rate in this study was low, with 2 patients reporting incontinence, 2 patients reporting rectal pain, and 2 patients reporting urinary retention. Of note, roughly two thirds of the patients in this cohort had received neoadjuvant hormonal therapy, the survival impact of which is still unclear in association with cryosurgery.
The largest series of patients to date, with the longest follow-up, included 590 subjects followed for a mean of 5.4 years[28]. Using an absolute PSA threshold of 0.5 ng/ml to define failure (as in many surgical series), the bDFS rates were 61%, 68%, and 61% for low-, intermediate-, and high-risk subjects. Adapting the ASTRO definition of failure (ie, 3 successive rises in PSA level), the bDFS rates were 92%, 89%, and 89%. Thirteen percent of subjects had positive biopsy findings; of these, 32 underwent repeat cryoablation, with 7-year bDFS rates comparable to those who had primary cryoablation only: 68% using the 0.5 ng/ml threshold and 91% using the ASTRO definition. Relatively few late failures occurred beyond 24-36 months.
Salvage therapy
Patients who experience disease progression after radiation therapy have few options for potentially curative therapy. Cryosurgery has been offered to such patients if they have no evidence of metastatic disease and their progression is thought to be restricted to persistent or recurrent local cancer. Recent series have demonstrated promising results for this treatment approach. Using 2 freeze-thaw cycles, a negative biopsy rate of 93% and a biochemical failure-free survival rate of 66% was achieved in a series of 150 subjects, although these results came at the price of higher complication rates. Subjects with preoperative PSA levels of more than 10 ng/ml or biopsy Gleason scores of more than 8 were most likely to experience disease recurrence[24].
A biochemical failure-free survival rate of 66% at 12 months was reported in a series of 43 salvage patients, with lower complication rates; additionally, a PSA nadir of more than 0.1 ng/ml following treatment predicted eventual recurrence. With the use of an argon-based cryosurgery system to treat 38 patients with biochemical recurrence after radiation, PSA nadirs less than 0.1 ng/ml were reported in 81.5% and bDFS rates of 86% and 74% were reported at 1- and 2-year follow-up, respectively[38].
In a large series, also using an argon-based system, 118 subjects with recurrent disease after radiation therapy underwent cryoablation, including 5 who had received permanent interstitial implants. Negative biopsy findings were reported in 94% of these patients; the 7 who had persistent disease received second ablation procedures. Ninety-seven percent had PSA nadirs less than 0.5 ng/ml; at a median of 18.6 months of follow-up, 34% remained below this level (68% had PSA levels <4 ng/ml). Ten patients had developed metastatic disease. Preprocedure PSA levels of more than 10 ng/ml, Gleason scores of more than 8, and stage T3-T4 disease predicted biochemical failure[39].
Seven-year outcomes for 59 patients treated with cryosurgery for failure after radiation were recently reported. The bDFS rate was 59% using a PSA threshold of 0.5 ng/ml and 69% using a threshold of 1 ng/ml. Notably, no patient had local recurrence upon repeat biopsy; all failures were presumably due to distant progression[40].
Adverse effects
Impotence
Cryosurgery impairs the penile arterial blood supply and damages the cavernosal nerves responsible for erectile function.A pooled analysis of 975 patients treated at 5 institutions from 1993-1998 revealed an impotence rate of 93%. However, a different report indicated that 3 years after cryoablation, 5 (13%) of 38 subjects had regained potency and 13 (34%) were potent with the help of erectile aids[28,41,42].
Incontinence
Rates of incontinence vary from 4% to 27% for patients given cryosurgery as primary treatment.Among patients undergoing cryosurgery for salvage treatment after failure of radiation therapy, the prevalence of incontinence is higher, ranging from 7.9% to 95.5%[38,43].
Tissue sloughing
If the urethra freezes during treatment, the necrotic prostate tissue may slough into the urethra, producing irritative and obstructive voiding symptoms, pyuria, and, possibly, urinary retention. The use of urethral warming devices significantly reduces the risk of this complication[24,36].
Pelvic and rectal pain
One to 11% of patients receiving primary cryosurgery and 21%-77% of those receiving salvage therapies for radiation failure have pelvic and/or rectal pain. The pain is best managed with anti-inflammatory medications[24,39].
Penile numbness
In early studies, approximately 10% of patients treated with cryosurgery developed penile numbness attributable to injury to the dorsal nerve of the penis. This complication was usually temporary, resolving spontaneously in approximately 2-3 months[21].
Rectourethral fistula
Complete freezing of tissues posterior to the prostate, with urinary extravasation and possible subsequent infection, can lead to fistula formation, which is reported in 0% to 3% of primary cryosurgery patients. In a large, recent series of salvage cases, however, only 4 cases were reported among 118 patients[41].
Urethral stricture
This is a rare complication when urethral warming is used and can usually be successfully managed with transurethral incision or balloon dilation.
DISCUSSION
Selection of cryosurgery mode
The original LN2-based freezing equipment has now been replaced by argon gas systems. These systems allow faster freezing rates, which improves the reliability of cancer destruction. The more precise control of the freezing process by gas systems also adds to the safety of the procedure by allowing the freezing process to be stopped in a more timely fashion[27].
Increasing the number of probes from 5 to 8 has allowed a more uniform freezing temperature to be achieved throughout the gland, which also improves results. There was an advantage to using 6-8 argon gas probes over 5 liquid nitrogen probes.
However, it is showed that increasing the number of probes beyond 8 could have a potentially negative effect. A "cryoseed system" that utilizes 17-gauge needle probes to create a 1-cm diameter iceball was not able to totally ablate the prostate gland based on reported PSA results. These poor results are probably the result of the short freezing length of these probes and the difficulty in accurately overlapping the freezing zones along the length of the gland.
Prostate parenchyma-sparing cryosurgery
It is suggested that prostate parenchyma-sparing cryosurgery may improve outcomes in terms of continence and potency. In a pilot program at the University of California at San Francisco, 8 patients with localized prostate cancer likewise have been treated with unilateral cryosurgery. All are disease-free, either based on PSA criteria or based on negative biopsy results. No patient developed a urethral fistula or significant tissue sloughing. Significantly, although only 2 of the patients were potent before treatment, both reported no change in their erections after the limited cryosurgical treatment[43,44].
Saline injectioniInto Denonvilliers' fascia
Probably the most important advance in the technique of prostate cryosurgery leading to the reproducibility of results involves the injection of saline into Denonvilliers' fascia at the time of freezing to temporarily increase the space between the rectum and prostate. This maneuver virtually eliminates the risk of rectal freezing and the complication of urethro-rectal fistula without increasing morbidity[45].
Temperature monitoring in critical areas and improved cryosurgical protocols
For reliable destruction of cancer by freezing, temperatures must reach certain critical limits. At least two freeze-thaw cycles with temperatures reaching -35°C are needed to reliably destroy prostate cancer cells. These parameters as well as the improvement that can occur in clinical results when temperature is monitored by thermocouples placed in critical areas in the prostate and two full freeze-thaw cycles are carried out[45].
Improvements of guiding techniques
Since the freezing capabilities of cryoprobes are predictable, planning software is already being developed to direct proper cryoprobe placement based on gland size and shape. Planning software will shortly be coupled to guidance software and hardware, which will simplify what now is a totally freehand approach to cryoprobe placement[45,46].
While ultrasound is inexpensive and readily available, it still is highly operator dependent and difficult to use by novices. Other cross-sectional imaging techniques such as MR imaging (MRI) have the potential to simplify and standardize cryosurgical procedures. As opposed to ultrasound, where ice causes shadowing and shows only the leading edge of the iceball, both MRI and computed tomography (CT) show the full extent of the freezing. Using thermodynamic equations, these images can then be used to noninvasively calculate temperatures within the ice-ball and automatically control the cryoprobes to create a specific freezing shape and profile[46].
CONCLUSION
Because of continuous technical development for more than half a century, followed by better clinical results with minimal side effects, cryosurgery of the prostate for localized prostate cancer has evolved as a true alternative therapeutic option in selected cases. The introduction of gas-based third-generation cryotechnology has significantly decreased side effects with high efficacy for treatment of high-risk carcinomas and failures of other therapeutic modalities. Cryosurgery of the prostate is indicated if there are absolute or relative contraindications for radical surgery. In localized prostate cancer, cryosurgery is the therapy of choice for most cases.

 

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