Experimental basis for hepatic cryotherapy

Hepatic tumor ablation: application in a community hospital setting

Primary liver tumors are a common clinical problem in the United States and worldwide. Resection has historically been used to treat liver lesions. Commonly used liver-directed therapies include transarterial chemoembolization, selective internal radiation therapy, and ablative therapy. Only ablative therapy can cause direct destruction of the targeted tissue. The commercially available modalities in the United States are all based on thermoablative technology. This article examines the various ablative technologies and their application, as well as how these procedures can be performed safely and with optimal outcomes, in a community cancer center.

Endoscopic cryosurgery of the thyroid and parathyroid

In this study we looked at the efficacy of cryosurgery for thyroid and parathyroid tissue ablation in the porcine model. An endoscopic neck approach was successfully used in six 25 kg pigs. T4, free T4 and calcium serum levels were measured pre- and post-operatively. Gross and histologic examination of the glands and surrounding tissue were performed on postoperative Day 40. Postoperative T4, free T4 and calcium levels were not significantly different from preoperative values. Gross examination of the thyroid showed scar tissue in the region that underwent cryosurgery. Parathyroid that was frozen was replaced by scar tissue. Histologic examination of the glands confirmed the gross findings. Trachea, vagus nerve and carotid artery were also resected, and no changes were noted on histological examination. There was no damage to the surrounding tissues after cryosurgery. Directed cryosurgery of the thyroid and parathyroid is safe and feasible in this model.

Cryosurgery for resectable and unresectable hepatic metastases from colorectal cancer

AIMS

Hepatic cryosurgery is useful for patients with hepatic metastases from colorectal cancer confined to the liver but considered unresectables because of the number and location of lesions. While encouraging results were reported following cryosurgery for unresectable liver metastases we considered particularly valuable to examine the safety and effectiveness of cryosurgery in patients with resectable and unresectable metastases from colorectal cancer.

METHODS

Between January 1997 and September 2005, 53 patients with liver metastases from colorectal cancer underwent hepatic cryosurgery at our institution. Hepatic metastases were resectable in 31 (58.5%) patients and unresectable in 22 (41.5%).

RESULTS

A total of 136 liver metastases were treated in 53 patients. The size of treated lesions ranged from 0.5 to 10 cm (mean 2.7). There were 2 postoperative deaths (3.8%) from massive bleeding and from cryoshock. The overall morbidity rate was 66%. The median follow-up was 24.8 months. The overall survival rate at 12 months was 86.1%, at 48 months it was 27%. No significant difference was found between survival rates in patients with resectable or unresectable metastases. Among 31 patients with resectable liver metastases 7 (22.6%) patients developed recurrence at the site of cryosurgery.

CONCLUSION

Survival rates were comparables between patients with resectable and unresectable metastases but a high complication rate and a substantial rate of local recurrence following cryosurgery should caution against its use to treat resectable disease.

Cryotherapy: Clinical end points and their experimental foundations

More renal tumors are now being found at an early stage. Similarly, the treatment of patients with such small tumors is shifting away from radical nephrectomy toward nephron-sparing extirpative surgery or nonextirpative renal tumor ablation. Of the various techniques used for renal tumor ablation, cryotherapy is the most extensively studied and has the longest reported outcomes. In this article, we examine the experimental and clinical evolution of cryotherapy for small renal masses. A literature search was performed with the following key words: cryobiology, cryotherapy, cryoablation, tissue-ice interaction, temperature, monitoring, cryoinjury, renal function, blood pressure, and treatment end point. Articles that dealt with the experimental and clinical bases of current cryoablation principles and techniques were selected for review. Some recent studies representative of current clinical outcomes were also examined. Cryotherapy for the small renal tumor can be performed during open surgery, laparoscopically, or even percutaneously with use of a variety of probes and high-resolution imaging techniques to monitor therapy. In the clinical scenario, the ice ball is usually extended 1 cm beyond the visible tumor margin. Cryotherapy per se does not adversely affect renal function and blood pressure. Inadvertent cryoinjury to the collecting system rarely leads to urinary leakage. To date, only 6-month follow-up biopsy data are available. Absence of contrast enhancement on follow-up computed tomography or magnetic resonance imaging is considered oncologic success. For a sporadic unilateral renal tumor, 98% cancer-specific survival at 3 years has been reported. Cryotherapy has moved beyond the "experimental" stage, and initial outcomes are encouraging. The major criticism of this and other ablative techniques is the associated lack of histologic confirmation of complete tumor ablation. Long-term, diligently performed studies that provide detailed, meticulous, sequential 5-year radiologic and histologic data are necessary to confirm lasting efficacy. In addition, these data must be compared with those related to partial nephrectomy, which remains the reference standard.

Cryoablation of liver tumours -- a review of mechanisms, techniques and clinical outcome

Several techniques exist for in situ destruction or ablation of liver tumours not eligible for resection. Cryoablation, i.e. the use of low temperatures to induce local tissue necrosis, was among the first of the thermal ablative techniques widely used. The procedures have typically been performed by surgeons during laparotomy, but recently minimally invasive cryoablation has been reported feasible. The present review focuses on mechanisms of tissue destruction, techniques of ablation including procedural monitoring, and clinical outcome following cryoablation of liver tumours. Plausible causes of tumour persistence at the site of ablation, i.e. local treatment failure, are discussed. Shortcomings exist in monitoring of the freezing process and may be a main cause. The evidence for the long-term outcome following liver tumour cryoablation needs to be improved. Cryoablation has been challenged by other techniques of tumour ablation such as radiofrequency ablation. Randomised trials against these modern techniques may define the role of cryoablation in the treatment of liver tumours. With improved imaging technology and patient selection, cryoablation of liver tumours may hold promise for selected patients.

Effect of fibrous capsule formation on doxorubicin distribution in radiofrequency ablated rat livers

In this study, we report the histological findings of a combined therapy using radiofrequency ablation and intratumoral drug delivery in rat livers, with special attention to wound-healing processes and their effects on drug transport in post-ablated tissue. Doxorubicin-loaded millirods were implanted in rat livers that had undergone medial lobe ablation. Millirods and liver samples were retrieved upon animal sacrifice at time points ranging from 1 h to 8 days. Results demonstrate a clearly defined area of coagulative necrosis within the ablation boundary. The wound-healing response, complete with the appearance of inflammatory cells, neovascularization, and the formation of a fibrous capsule, was also observed. At the 8-day time point, fluorescence imaging analysis showed a higher concentration of doxorubicin localized within the ablation region, with its distribution hampered primarily by fibrous capsule formation at the boundary. Given the variant nature of ablated liver, a mathematical model devised previously by our laboratory describes the data well up to 4 days, but loses reliability at 8 days. These results provide useful mechanistic insights into the wound-healing response after radiofrequency ablation and polymer millirod implantation, as well as the impact this natural corollary has on drug distribution.

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.

Renal cryotherapy: 2003 clinical status

PURPOSE OF REVIEW

Traditionally, curative therapy for most renal cancers involved open radical nephrectomy. However, as increased radiological monitoring has led to more incidentally discovered small renal masses, the optimal treatment has evolved. Nephron-sparing surgery, initially developed for patients with solitary kidneys or compromised renal function, emerged as the treatment of choice for small renal masses. It has been shown that long-term cancer control and renal function after partial nephrectomy equals the results of radical nephrectomy. Cryoablation of small renal masses represents an alternative method for performing nephron-sparing surgery.

RECENT FINDINGS

Cryoablation of renal tumors with ultrasound monitoring may be performed under open exposure, but laparoscopy provides equivalent exposure with less morbidity. Cryotherapy may also be performed percutaneously with magnetic resonance image monitoring. After treatment, patients require diligent radiographic monitoring, more frequently than after surgical extirpation.

SUMMARY

The durability of renal cryotherapy appears promising. More data are required to provide reliable treatment of tumor margins for larger lesions, and further to determine the safety of use near the collecting system and renal hilum. Currently, cryoablation of small renal lesions is minimally invasive, safe, and efficacious for select peripheral lesions in carefully selected patients.

Magnetic resonance imaging-estimated three-dimensional temperature distribution in liver cryolesions: a study of cryolesion characteristics assumed necessary for tumor ablation

The goal of this study was to estimate the three-dimensional (3D) temperature distribution in liver cryolesions and assess the margin of the transition zone between the tumoricidal core of the lesion and the surrounding unfrozen tissue, using criteria proposed in the literature. Local recurrences after liver tumor cryoablation are frequent. Temperatures below -40 degrees C and a 1-cm zone of normal tissue included in the cryolesion are considered necessary for adequate ablation. The 3D temperature distribution in 10 pig cryolesions was estimated by numerical solution of a simplified bioheat equation using magnetic resonance imaging data to establish cryolesion border conditions. Volumes encompassed by the -20, -40, and -60 degrees C isotherms were estimated. The shortest distance from every voxel on the -40 degrees C isotherm to the cryolesion edge was calculated and the mean and the maximal of these distances were defined for each cryolesion. Median cryolesion volumes with temperatures of -20, -40, and -60 degrees C or colder were 53, 26, and 14% of the total cryolesion volume, respectively. The median cryolesion volume was 12.3 cm(3). The median of the mean distances calculated between the -40 degrees C isotherm and the cryolesion edge was 4.1 mm and increased with increasing cryolesion volume. The median of the largest of these distances calculated for each cryolesion was 8.1 mm. Temperatures claimed to be adequate for tumor destruction were obtained only in parts of the cryolesion. The adequacy of a 1-cm zone of normal liver tissue included in the cryolesion to ensure tumor ablation is questioned.