Cryosurgical Ablation of the Prostate
Principles of the technique and the Grant/Riemenschneider experience, October 2001 - March 2003
More information on Cryosurgery and prostate cancer available here
Definition of Cryotherapy - Invitro freezing and destruction of tissue that can be applied and controlled precisely to produce a predictable zone of tissue death that will destroy the "target lesion" (bad cells) as well as an appropriate margin of surrounding tissue (J Surg Oncology, 1966; 256-264).
The third generation cryo-probe is a needle that has fantastic engineering built into it. The caliber of the cryo probe is the same as needles that are used to draw blood from a patient's arm when obtaining lab work. This cryo probe has the ability to produce very cold temperatures and results in the formation of "lethal ice". This probe also has the capacity to transmit heat through the probe to stop the growth of the ice ball.
The mechanism by which these cold temperatures kill the target cells occurs in three ways. First, the extracellular ice formation occurs at -7 degrees centigrade. Second, ice crystals form between the cells and in so doing, dehydrates the space which draws water from the cells causing the cells to dehydrate. Three, the dehydration destroys or severely injures the biological mechanism of the cell that keeps it alive.
The history of cryosurgery tells us that the early cryo probes were very large and the cooling agent was liquid nitrogen. This agent is very effective resulting in very cold temperatures and hard freezes. These probes had no warming element and therefore, the freeze was very difficult to control. The second-generation cryo probes were smaller and used Argon gas as the cryogen, was more controllable than liquid nitrogen and includes a heating element that is based on the expansion of Helium gas being pumped through the probe at the right time.
The third generation cryo probe uses Argon for freezing and Helium for heating. It is much smaller than the second generation probes, it is a 17-gage needle. This needle is so small it can be placed with pinpoint accuracy at the time of freeze and will result in the cell death cycle which occurs at the target tissue.
Another way to understand why the small probes produce a more uniform isotherm jus think of the difference between filling a fishbowl with marbles versus bb's. The bb's are closer together, the freeze is more uniform and results in predictable constant low temperature (the isotherm) that then results in a very predictable kill of the target tissue.
These features allow the cryosurgeon to sculpt the ice ball so that it fits the precise anatomy of the target tissue.
The freezing mechanism is based on what is known as the Joule Thompson effect. When high pressure Argon is allowed to flow through the cryo probe, as it expands at the tip, it generates a very cold temperature. When a relay is changed and high pressure helium gas goes through the cryo probe when it expands at the tip, heat is generated.
The cryosurgical ablation of prostate cancer has been applied for treatment of this disease since the late 1980's. On October 28, 2001, Dr. Riemenschneider, in conjunction with Grant hospital, began the Central Ohio experience with the third generation cryosurgical system. 41 cases for treatment of prostate cancer have been completed. We report here on 38 of those cases.
Grant Hospital
The Grant/Riemenschneider experience of the first 38 patients included 74% of patients were treated primarily with cryotherapy, meaning it was the only treatment strategy used. 26% of this group had cryotherapy used to treat prostate cancer which had failed in other treatment. In all instances in this series, it was failure of radiation therapy.
Initial presentation of the PSA of the 38 patients and it can be noted that the PSA was well above 1 in many cases, 10 or greater in the pre-cryo treatment phase.
Three month follow up after surgery.
After cryosurgical treatment, it can be seen that the majority of PSA determinations in the same group of patients was now very low and in most instances less than 0.1.
Biopsies are performed at 6, 12 and 18 months. Twenty-one patients were biopsied at 6 months and none of the biopsies were positive.
Demonstrates the sculpting of the ice ball using both the ultrasound probe in the rectum and the thermo sensors designed to protect the tissues adjacent to the prostate from lethal freezing.
This also demonstrates the cryo probes in place in the prostate as the freeze occurs.
Prostate after placement of cryo probe
Ultrasound of the prostate after placement of the cryo probes
Ultrasound demonstrating the lethally frozen prostate near the end of the procedure
Statistics from American cancer society
The Grant/Riemenschneider cryosurgical data is young. However, comparing our statistics with 10-year data from Allegheny general hospital, a more mature data set, our data parallels the early phases of the Allegheny study
Demonstrates the goals of cryoablation
Our cryo program data has been analyzed between the dates of October 2001 and March 2003 and demonstrate the following findings:
The Grant/Riemenschneider cryo program data analyzed between October of 2001 and March of 2003 demonstrate the following findings.
1) 38 patients have been treated to date
2) There were no positive biopsies in 21/38 patients at the first biopsy interval of 6 months - 100% of biopsies were negative
3) At the 12-month biopsy interval, 1/7 patients demonstrated a positive biopsy. 86% of the patients had a negative biopsy rate at 12 months.
4) Most PSA's at 6, 12 and 18 months have been less than 0.5 and many have been < 0.1ng/ml.
5) There is no incontinence in this group to date.
6) Half of the patients have regained potency either spontaneously or with Viagra or penile injections
7) Third generation 17-guage cryo probe delivers cryo therapy that is very effective in eliminating prostate cancer that is confined.