In vitro and in vivo assessment of urethral warming catheters for the transperineal cryoablation of prostatic carcinoma

Enhanced killing of HepG2 during cryosurgery with Fe3O4-nanoparticle improved intracellular ice formation and cell dehydration

Cryosurgery is a minimally invasive treatment that utilize extreme low temperatures to destroy abnormal tissues. The clinical monitoring methods for cryosurgery are almost based on the visualization of the iceball. However, for a normal cryosurgery process, the effective killing region is always smaller than the iceball. As a result, the end of the cryosurgery process can only be judged by the surgeons according to their experience. The subjective judgement is one of the main reasons for poor estimation of tumor ablation, and it sparks high probability of recurrence and metastasis associate with cryosurgery. Being different from the previous optimization studies, we develop a novel approach with the aid of nanoparticles to enlarge the effective killing region of entire iceball, and thus it greatly decrease the difficulty of precise judgement of the cryosurgery only by applying the common clinical imaging methods. To verify this approach, both the experiments on a tissue-scale phantom with embedded living HepG2 cells in agarose and on a cell-scale cryo-microscopic freeze-thaw stage are performed. The results indicate that the introduction of the self-synthesized Fe3O4 nanoparticles significantly improved cell killing in the cryosurgery and the range of killing is extended to the entire iceball. The potential mechanism is further revealed by the cryo-microscopic experiments, which verifies the presence of Fe3O4 nanoparticles can significantly enhance the probability of intracellular ice formation and the cell dehydration during freezing hence it promote precise killing of the cells. These findings may further promote the widespread clinical application of modern cryosurgery.

Thermal Protection during Percutaneous Thermal Ablation of Renal Cell Carcinoma

Thermal injury to collateral structures is a known complication of thermal ablation of tumors. The authors present the use of CO(2) dissection and inserted balloons to protect the bowel during percutaneous radiofrequency (RF) ablation and cryotherapy of primary and locally recurrent renal cell carcinoma. These techniques offer the potential to increase the number of tumors that can be treated with RF ablation or cryotherapy from a percutaneous approach.

Effect of intentional cryo-injury to the renal collecting system

PURPOSE

We determined the short-term and long-term sequelae of intentional cryoablation of the renal pelvicaliceal system and evaluated whether continuous irrigation of the renal pelvicaliceal system with warm saline protects it against cryo-injury.

MATERIALS AND METHODS

In 12 swine open bilateral renal cryoablation using an argon gas based system was performed to create a cryolesion in the lower pole that was intentionally extended into the collecting system. A single cryoprobe was used to create a 3 cm ice ball in group 1 (6 animals) and 2, 3 mm cryoprobes were used to create a 4.5 cm ice ball in group 2 (6). In all 12 right kidneys pelvicaliceal warming (range 38C to 42C) was performed using continuous retrograde saline irrigation through an indwelling 5Fr ureteral catheter. In all 12 left kidneys cryoablation was performed without pelvicaliceal warming. Real-time confirmation of caliceal involvement by the cryolesion was obtained by retrograde ureteropyelogram. Immediately after cryo-injury 6 left and 6 right kidneys were harvested for histology and the animals with a solitary kidney were followed for 1 to 3 months.

RESULTS

Nadir cryoprobe tip temperature was -136C with a mean cryolesion time of 10.5 minutes. Cryolesion size was comparable in the right vs left kidneys in groups 1 and 2 (2.9 vs 3.0 and 4.7 vs 4.6 cm, respectively). Similarly cryoablation time was comparable between the right and left kidneys in groups 1 and 2 (11.3 vs 10.8 and 11.9 vs 12.2 minutes, respectively). Two animals died of aspiration pneumonia (1) and wound dehiscence (1). In all 10 surviving animals no instance of urinary extravasation was noted. At 1-month followup regrowth of normal urothelium occurred with some scarring of the lamina propria or underlying smooth muscle. Adjacent renal parenchyma was replaced by fibrous scar. At 3 months the cryo-injured collecting system was completely healed with a fibrous scar. There were no appreciable histological differences between the kidneys with or without warm pelvicaliceal irrigation.

CONCLUSIONS

Our data suggest that absent physical puncture injury of the collecting system with the cryoprobe tip the cryodamaged renal collecting system heals by secondary intention in a watertight manner. These data have clinical relevance for facilitating cryoablation of a small, localized, central renal tumor in proximity to the pelvicaliceal system.

Theoretical modelling, experimental studies and clinical simulations of urethral cooling catheters for use during prostate thermal therapy

Urethral cooling catheters are used to prevent thermal damage to the urethra during thermal therapy of the prostate. Quantification of a catheter's heat transfer characteristics is necessary for prediction of the catheter's influence on the temperature and thermal dose distribution in periurethral tissue. Two cooling catheters with different designs were examined: the Dornier Urowave catheter and a prototype device from BSD Medical Corp. A convection coefficient, h. was used to characterize the cooling ability of each catheter. The value of the convection coefficient (h = 330 W m(-2) C(-1) for the Dornier catheter. h = 160 W m(-2) C(-1) for the BSD device) was obtained by comparing temperatures measured in a tissue-equivalent phantom material to temperatures predicted by a finite element method simulation of the phantom experiments. The coefficient was found to be insensitive to the rate of coolant flow inside the catheter between 40 and 120 ml min(-1). The convection coefficient method for modelling urethral catheters was incorporated into simulations of microwave heating of the prostate. Results from these simulations indicate that the Dornier device is significantly more effective than the BSD catheter at cooling the tissue surrounding the urethra.

Proximity of prostate cancer to the urethra: implications for minimally invasive ablative therapies

OBJECTIVES

The delivery of thermotherapy, cryotherapy, and interstitial radiation with minimal morbidity is dependent on the preservation of the prostatic urethra. Our aim was to determine the distribution of the distance between the urethra and the nearest prostate cancer.

METHODS

We determined the location of cancer in 350 prostate cancers treated by radical prostatectomy between 1991 and 1993. Each pathologic specimen was totally embedded, serially sectioned, and whole mounted. For each prostate, the radial distance from the urethra to the nearest cancer was determined (urethral-cancer distance). The urethra-cancer distance was correlated with the clinical, pathologic, and laboratory factors. Univariate and multivariate associations with progression-free survival were determined.

RESULTS

The mean follow-up was 6.1 years. Ninety-three patients had biochemical, local, or systemic cancer recurrence. The mean +/- SD distance from the urethra to the nearest cancer was 3 +/- 3 mm (range 0 to 18). In 58 patients (17%), the cancer touched the urethra. A decreasing urethra-cancer distance was associated with increasing rates of cancer recurrence (P = 0.009). The urethra-cancer distance correlated with each of the following preoperative factors: preoperative prostate-specific antigen (r = -0. 22, P <0.001), Gleason score in biopsy specimen (r = -0.13, P = 0.02), and percentage of Gleason score 4 or 5 in the biopsy specimen (r = -0.17, P = 0.008).

CONCLUSIONS

The distance between the urethra and the nearest cancer was associated with prostate cancer outcome. Many patients have cancer close to the urethra. This finding may have implications for nonsurgical ablative therapies for prostate cancer.

Cryosurgery for prostate cancer: new technology and indications

Patients diagnosed with prostate cancer who elect to pursue active treatment of their disease must choose among the many available treatment alternatives. Several treatment options now exist for similar-stage disease (clinical T1-3N0M0), including radical prostatectomy, external beam radiation, prostate brachytherapy (PB), and cryosurgical ablation of the prostate (CSAP). This article reviews the current role of CSAP in the treatment of clinically localized prostate cancer. CSAP has a role in the primary treatment of men with high-risk, clinically localized prostate cancer (defined as PSA >10, Gleason score >or=7, or clinical stage >or= cT2B). CSAP (occasionally followed by external beam radiotherapy) appears to offer improved rates of cancer control over other types of single or combination therapies for this high-risk prostate cancer, and it is associated with an acceptable side-effect profile. CSAP should also be the treatment of choice for men with recurrent local disease who have undergone external beam radiotherapy or PB.

Cryotherapy for neuroendocrine liver metastases

While the prognosis for patients with untreated liver metastases from neuroendocrine primaries is rather good, they often suffer disabling symptoms due to syndromes of hormonal excess. Thirteen patients with metastatic neuroendocrine tumours were treated by hepatic cryotherapy; seven patients were symptomatic and five of these had elevated levels of hormonal tumour markers. Twelve patients are alive and mostly asymptomatic with a median follow up of 13.5 months; one patient died after 45 months of bronchopneumonia without evidence of tumour recurrence. All patients with elevated preoperative tumour markers have had a significant fall in markers postoperatively. Two patients were returned to the operating theatre for coagulopathy-associated bleeding: one patient each developed acute renal failure and pulmonary embolism, but there was no mortality. This study shows that hepatic cryotherapy offers a useful treatment option for this group of patients, alleviates symptoms and may have an impact on survival.

Bile duct warmer in hepatic cryosurgery--a pig liver model

Freezing of the common bile duct resulted in injury, stenosis, or perforation of the bile duct in a dog model. Biliary cutaneous fistulas and bile leaks are reported as complications of hepatic cryosurgery in man. In an ex vivo pig liver model we compared freezing close to the bile duct with and without warming the bile duct with warmed saline solution via an inserted catheter ("bile duct warmer"). The recorded temperatures at the outer wall of the bile duct were -50 degrees C after 10 min of freezing without and 5. 8 degrees C with the use of the warmer (P < 0.001, two-way ANOVA). The bile duct warmer system may be a simple and inexpensive device in reducing perioperative morbidity after hepatic cryosurgery of hepatic liver lesions close to a bile duct.