Experimental cryosurgery investigations in vivo

Assessment of Cryosurgical Device Performance Using a 3D Tissue-Engineered Cancer Model

As the clinical use of cryoablation for the treatment of cancer has increased, so too has the need for knowledge on the dynamic environment within the frozen mass created by a cryoprobe. While a number of factors exist, an understanding of the iceball size, critical isotherm distribution/penetration, and the resultant lethal zone created by a cryoprobe are critical for clinical application. To this end, cryoprobe performance is typically characterized based on the iceball size and temperature penetration in phantom gel models. Although informative, these models do not provide information as to the impact of heat input from surrounding tissue nor give any information on the ablative zone created. As such, we evaluated the use of a tissue-engineered tumor model (TEM) to assess cryoprobe performance including iceball size, real-time thermal profile distribution, and resultant ablative zone. Studies were conducted using an Endocare V-probe cryoprobe, with a 10/5/10 double freeze–thaw protocol using prostate and renal cancer TEMs. The data demonstrate the generation of a 33- to 38-cm3 frozen mass with the V-Probe cryoprobe following the double freeze of which ∼12.7 and 6.5 cm3 was at or below −20°C and −40°C, respectively. Analysis of ablation zone using fluorescence microscopy 24 hours postthaw demonstrated that the internal ∼40% of the frozen mass was completely ablated, whereas in the periphery of the iceball (outer 1 cm region), a gradient of partial to minimal destruction was observed. These findings correlated well with clinical reports on renal and prostate cancer cryoablation. Overall, this study demonstrates that TEMs provide an effective model for a more complete characterization of cryoablation device performance. The data demonstrate that while the overall iceball size generated in the TEM was consistent with published reports from phantom models, the integration of an external heat load, circulation, and cellular components more closely reflect an in vivo setting and the impact of penetration of the critical (−20°C and −40°C) isotherms into the tissue. This is important as it is well appreciated in clinical practice that the heat load of a tissue, cryoprobe proximity to vasculature, and so on, can impact outcome. The TEM model provides a means of characterizing the impact on ablative dose delivery allowing for a better understanding of probe performance and potential impact on ablative outcome.

Characterization of the cryoablation-induced immune response in kidney cancer patients

Cryoablation is one of treatment modalities for kidney cancer and is expected to induce strong local immune responses as well as systemic T-cell-mediated immune reactions that may lead to the regression of distant metastatic lesions. Thus, the characterization of T cell repertoire and immune environment in tumors before and after treatment should contribute to the better understanding of the cryoablation-induced anticancer immune responses. In this study, we collected tumor tissues from 22 kidney cancer patients, before cryoablation and at 3 mo after cryoablation. In addition, blood samples were collected from 14 patients at the same time points. We applied a next generation sequencing approach to characterize T cell receptor β (TCRB) repertoires using RNAs isolated from tumor tissues and peripheral blood mononuclear cells. TCRB repertoire analysis revealed the expansion of certain T cell clones in tumor tissues by cryoablation. We also found that proportions of abundant TCRB clonotypes (defined as clonotypes with ≥ 1% frequency among total TCRB reads) were significantly increased in the post-cryoablation tissue samples than those of pre-cryoablation tumor samples. Some of these TCRB clonotypes were found to be increased in peripheral blood. Expression analysis of immune-related genes in the tissues of pre- and post-cryoablation showed significantly elevated transcriptional levels of CD8⁺ , CD4⁺ , Granzyme A (GZMA), and CD11c along with a high CD8/FOXP3 ratio in the post-cryoablation tissue samples. Our findings revealed that cryoablation could induce strong immune reactions in tumors with oligoclonal expansion of antitumor T cells, which circulate systemically.

A multicenter study of the need of additional freezing for cryoballoon ablation in patients with atrial fibrillation: The AD-Balloon study

Background

Pulmonary vein isolation (PVI) is a cornerstone of catheter ablation in patients with paroxysmal atrial fibrillation (PAF), and balloon-based ablation has been recently performed worldwide. Ablation using the second-generation cryoballoon (CB2) (Arctic Front Advance^TM, Medtronic, MN, USA) is useful for PVI; however, there is some debate concerning the optimal freezing time and number of cycles after PVI is achieved.

Methods

The AD-Balloon study was designed as a prospective, multicenter, randomized clinical trial to evaluate the optimal strategy (freezing cycles) of CB2 ablation (UMIN Clinical Trials Registry UMIN000020130). The main objective of this study is to investigate the need for an additional freezing cycle after PVI in patients treated with CB2 ablation. Patients will be randomly assigned in a 1:1 ratio to treatment with additional freezing (AD group) or without additional freezing (non-AD group). In the AD group, 3 min of additional freezing time will be applied in all pulmonary veins after PVI is confirmed at the previous freezing cycle. In the non-AD group, no additional freezing will be applied in all pulmonary veins after PVI is confirmed. The primary endpoint of this study is the occurrence of atrial tachyarrhythmias within a 1-year follow-up period. We will enroll 110 consecutive patients with PAF. We will also investigate the usefulness of delayed-enhancement magnetic resonance imaging to assess the ablation lesions caused by CB2 ablation.

Results

The results of this study are currently under investigation.

Conclusion

The AD-Balloon study would assess the need for an additional freezing cycle after PVI is achieved. Our findings may contribute to further improvement of the CB2 ablation procedure.

Use of refrigerant spray of a propane/butane/isobutane gas mixture in the management of keratocystic odontogenic tumors: a preliminary study

PURPOSE

Keratocystic odontogenic tumor (KCOT) is an aggressive benign tumor and the management by complete enucleation followed by cryotherapy maintains the inorganic bone matrix, resulting in better repair and reduces the rates of recurrence. A refrigerant spray with a propane/butane/isobutane gas mixture has been pointed to as an alternative to liquid nitrogen, because the device is easy to handle and contain within the cavity, providing better control and lower risk of injury to the adjacent soft tissue. Thus, the aim of this study was to evaluate the outcome of enucleation followed by cryosurgery using a refrigerant spray of this gas mixture in ten patients diagnosed with KCOT.

METHOD

The biggest lesions received a prior treatment consisting of marsupialization to decrease the tumor size. During the surgeries, the lesions were removed by enucleation and the surgical site was sprayed with the gas mixture.

RESULTS

Wound dehiscence was observed in all cases, which healed by the second intention. The mean follow-up period was 64.3 months (range 24-120 months). Eight of the ten patients showed no evidence of clinical or radiographic recurrence. Pathologic fractures and infections were not observed.

CONCLUSIONS

The results obtained suggest that enucleation followed by cryosurgery is an effective therapy for managing KCOT.

Thermal Conductivity of Human Bone in Cryoprobe Freezing as Related to Density

Cryoprobes create localized cell destruction through freezing. Bone is resistant to temperature flow but is susceptible to freezing necrosis at warmer temperatures than tumor cells. Few studies have determined the thermal conductivity of human bone. No studies have examined conductivity as related to density. The study goal was to examine thermal conductivity in human bone while comparing differences between cancellous and cortical bone. An additional goal was to establish a relationship between bone density and thermal conductivity. Six knee joints from 5 cadavers were obtained. The epiphyseal region was sliced in half coronally prior to inserting an argon-circulating cryoprobe directed away from the joint line. Thermistor thermometers were placed perpendicularly at measured increments, and the freezing cycle was recorded until steady-state conditions were achieved. For 2 cortical samples, the probe was placed intramedullary in metaphyseal samples and measurements were performed radially from the central axis of each sample. Conductivity was calculated using Fournier's Law and then plotted against measured density of each sample. Across samples, density of cancellous bone ranged from 0.86 to 1.38 g/mL and average thermal conductivity ranged between 0.404 and 0.55 W/mK. Comparatively, cortical bone had a density of 1.70 to 1.86 g/mL and thermal conductivity of 0.0742 to 0.109 W/mK. A strong 2-degree polynomial correlation was seen (R²=0.8226, P<.001). Bone is highly resistant to temperature flow. This resistance varies and inversely correlates strongly with density. This information is clinically relevant to maximize tumor ablation while minimizing morbidity through unnecessary bone loss and damage to surrounding structures. [Orthopedics. 2017; 40(2):90-94.].

Cryoablation of atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) affects 1-2% of the population, and its prevalence is estimated to at least double in the next 50 years as the population ages.

AREAS OF AGREEMENT

AF results in impaired quality of life and even increased mortality. Drugs frequently fail to stabilize sinus rhythm.

AREAS OF CONTROVERSY

Catheter ablation is a valuable treatment alternative, even as a first-line therapy in selected cases. However, catheter ablation of AF is challenging, even for experienced operators.

GROWING POINTS

Simplification of catheter ablation of AF is essential to decrease the threshold for treatment, broaden the access to the therapy and contribute to further reduction of the disease burden. Single-shot devices, that are easy to navigate in the heart, are an essential element in efforts to reach this goal.

AREAS TIMELY FOR DEVELOPING RESEARCH

Cryoenergy is an excellent energy source to combine with a single-shot device, resulting in an excellent safety profile and good clinical results while maintaining its ease of use.

CT guided cryoablation for locally recurrent or metastatic bone and soft tissue tumor: initial experience

Background

Historically, local control of recurrent sarcomas has been limited to radiotherapy when surgical re-resection is not feasible. For metastatic carcinomas to the bone or soft tissue, radiotherapy and some interventional radiology treatment along with other systemic therapies have been widely advocated due to the possibility of disseminated disease. These techniques are effective in alleviating pain and achieving local control for some tumor types, but it has not been effective for prolonged local control of most tumors. Recently, cryoablation has been reported to have satisfactory results in lung and liver carcinoma treatment. In this study, we analyzed the clinical outcome of CT-guided cryoablation for malignant bone and soft tissue tumors to elucidate potential problems associated with this procedure.

Methods

Since 2011, 11 CT-guided cryoablations in 9 patients were performed for locally recurrent or metastatic bone and soft tissue tumors (7 males and 2 females) at our institute. The patients’ average age was 74.8 years (range 61–86) and the median follow up period was 24.1 months (range 5–48). Histological diagnosis included renal cell carcinoma (n = 4), dedifferentiated liposarcoma (n = 2), myxofibrosarcoma (n = 2), chordoma (n = 1), hepatocellular carcinoma (n = 1), and thyroid carcinoma (n = 1). Cryoablation methods, clinical outcomes, complications, and oncological outcomes were analyzed.

Results

There were 5 recurrent tumors and 6 metastatic tumors, and all cases had contraindication to either surgery, chemotherapy or radiotherapy. Two and 3 cycles of cryoablation were performed for bone and soft tissue tumors, respectively. The average length of the procedure was 101.1 min (range 63–187), and the average number of probes was 2.4 (range 2–3). Complications included 1 case of urinary retention in a patient with sacral chordoma who underwent prior carbon ion radiotherapy, 1 transient femoral nerve palsy, and 1 minor wound complication. At the final follow up, 4 patients showed no evidence of disease, 2 were alive with disease, and 3 died of disease.

Conclusions

Reports regarding CT-guided cryoablation for musculoskeletal tumors are rare and the clinical outcomes have not been extensively studied. In our case series, CT-guided cryoablation had analgesic efficacy and there were no cases of local recurrence post procedure during the follow-up period. Although collection of further data regarding use of this technique is necessary, our data suggest that cryoablation is a promising option in medically inoperable musculoskeletal tumors.

Deep Sequencing of T-cell Receptor DNA as a Biomarker of Clonally Expanded TILs in Breast Cancer after Immunotherapy

In early-stage breast cancer, the degree of tumor-infiltrating lymphocytes (TIL) predicts response to chemotherapy and overall survival. Combination immunotherapy with immune checkpoint antibody plus tumor cryoablation can induce lymphocytic infiltrates and improve survival in mice. We used T-cell receptor (TCR) DNA sequencing to evaluate both the effect of cryoimmunotherapy in humans and the feasibility of TCR sequencing in early-stage breast cancer. In a pilot clinical trial, 18 women with early-stage breast cancer were treated preoperatively with cryoablation, single-dose anti-CTLA-4 (ipilimumab), or cryoablation + ipilimumab. TCRs within serially collected peripheral blood and tumor tissue were sequenced. In baseline tumor tissues, T-cell density as measured by TCR sequencing correlated with TIL scores obtained by hematoxylin and eosin (H&E) staining. However, tumors with little or no lymphocytes by H&E contained up to 3.6 × 10⁶ TCR DNA sequences, highlighting the sensitivity of the ImmunoSEQ platform. In this dataset, ipilimumab increased intratumoral T-cell density over time, whereas cryoablation ± ipilimumab diversified and remodeled the intratumoral T-cell clonal repertoire. Compared with monotherapy, cryoablation plus ipilimumab was associated with numerically greater numbers of peripheral blood and intratumoral T-cell clones expanding robustly following therapy. In conclusion, TCR sequencing correlates with H&E lymphocyte scoring and provides additional information on clonal diversity. These findings support further study of the use of TCR sequencing as a biomarker for T-cell responses to therapy and for the study of cryoimmunotherapy in early-stage breast cancer. Cancer Immunol Res; 4(10); 835-44. ©2016 AACR.

Endoscopic applications of cryospray ablation therapy-from Barrett’s esophagus and beyond

In the last decade, the treatment of dysplastic Barrett’s esophagus has evolved into primarily endoscopic therapy. Many techniques have become well-established to destroy or remove the mucosal lining of Barrett’s esophagus. One of the newest therapies, cryospray ablation, has become a modality to treat both dysplastic Barrett’s esophagus as well as esophageal carcinoma. In endoscopic applications, the cryogen used is either liquid nitrogen or carbon dioxide which causes tissue destruction through rapid freeze-thaw cycles. Unlike other endoscopic ablation techniques, its unique mechanism of action and depth of tissue injury allow cryoablation to be used effectively in flat or nodular disease. It can be combined with other modalities such as endoscopic mucosal resection or radiofrequency ablation. Its esophageal applications stem well-beyond Barrett’s into ablation of early carcinoma, palliative debulking of advanced carcinoma and reduction of tumor ingrowth into stents placed for dysphagia. Although there are fewer reported studies of endoscopic cryoablation in the literature compared to other endoscopic ablation methods, emerging research continues to demonstrate its efficacy as a durable ablation technology with a variety of applications. The aim of this review is to examine the pathophysiology of endoscopic cryospray ablation, describe its outcomes in Barrett’s with dysplasia and esophageal carcinoma, and examine its role in other gastrointestinal applications such as hemostasis in the stomach and rectum.

A Review of Therapeutic Ablation Modalities

Understanding basic science and technical aspects is essential for scientists and engineers to develop and enhance ablative modalities, and for clinicians to effectively apply therapeutic ablative techniques. An overview of ablative modalities, anatomical locations, and indications for which ablations are performed is presented. Specifically, basic concepts, parameter selection, and underlying biophysics of tissue injury of five currently used therapeutic ablative modalities are reviewed: radiofrequency ablation (RFA), cryoablation (CRA), microwave ablation (MWA), high-intensity focused ultrasound (HIFU), and chemical ablation (CHA) (ablative agents: acetic acid, ethanol, hypertonic sodium chloride, and urea). Each ablative modality could be refined for expanding applications, either independently or in combination, for future therapeutic use.

Characterization of Pancreatic Cancer Cell Thermal Response to Heat Ablation or Cryoablation

One of the most lethal carcinomas is pancreatic cancer. As standard treatment using chemotherapy and radiation has shown limited success, thermal regimens (cryotherapy or heat ablation) are emerging as viable alternatives. Although promising, our understanding of pancreatic cancer response to thermal ablation remains limited. In this study, we investigated the thermal responses of 2 pancreatic cancer cell lines in an effort to identify the minimum lethal temperature needed for complete cell death to provide guidance for in vivo applications. PANC-1 and BxPC-3 were frozen (-10°C to -25°C) or heated (45°C-50°C) in single and repeated exposure regimes. Posttreatment survival and recovery were analyzed using alamarBlue assay over a 7-day interval. Modes of cell death were assessed using fluorescence microscopy (calcein acetoxymethyl ester/propidium iodide) and flow cytometry (YO-PRO-1/propidium iodide). Freezing to -10°C resulted in minimal cell death. Exposure to -15°C had a mild impact on PANC-1 survival (93%), whereas BxPC-3 was more severely damaged (33%). Exposure to -20°C caused a significant reduction in viability (PANC-1 = 23%; BxPC-3 = 2%) whereas -25°C yielded complete death. Double freezing exposure was more effective than single exposure. Repeat exposure to -15°C resulted in complete death of BxPC-3, whereas -20°C severely impacted PANC-1 (7%). Heating to 45°C resulted in minimum cell death. Exposure to 48°C yielded a slight increase in cell loss (PANC-1 = 85%; BxPC-3 = 98%). Exposure to 50°C caused a significant decline (PANC-1 = 70%; BxPC-3 = 9%) with continued deterioration to 0%. Double heating to 45°C resulted in similar effects observed in single exposures, whereas repeated 48°C resulted in significant increases in cell death (PANC-1 = 68%; BxPC-3 = 29%). In conclusion, we observed that pancreatic cancer cells were completely destroyed at temperatures <-25°C or >50°C using single thermal exposures. Repeated exposures resulted in increased cell death at less extreme temperatures. Our data suggest that thermal ablation strategies (heat or cryoablation) may represent a viable technique for the treatment of pancreatic cancer.

The cryoablation of lung tissue using liquid nitrogen in gel and in the ex vivo pig lung

PURPOSES

To examine the efficiency of cryoablation using liquid nitrogen in lung tissue, we measured the size and temperature distribution of the frozen area (iceball) in gel and in the ex vivo pig lungs.

METHODS

Cryoprobes with diameters of 2.4 and 3.4 mm (2.4D and 3.4D, respectively) were used. Three temperature sensors were positioned at the surface of the cryoprobe and at distances of 0.5 and 1.5 cm from the cryoprobe. The ex vivo pig lungs were perfused with 37 °C saline and inflated using ventilator to simulate in vivo lung conditions.

RESULTS

In gel, the 2.4D and 3.4D probes made iceballs of 3.9 ± 0.1 and 4.8 ± 0.3 cm in diameter, respectively, and the temperature at 1.5 cm from those probes reached -32 ± 8 and -53 ± 5 °C, respectively. In the pig lung, the 2.4D and 3.4D probes made iceballs of 5.2 ± 0.1 and 5.5 ± 0.4 cm in diameter, respectively, and the temperature at 1.5 cm from these probes reached -49 ± 5 and -58 ± 3 °C, respectively.

CONCLUSION

Liquid nitrogen cryoablation using both 2.4D and 3.4D probes made iceballs that were of sufficient size, and effective temperatures were reached in both gel and the ex vivo pig lung.

Percutaneous Image-Guided Musculoskeletal Tumor Treatments

OBJECTIVE

The purpose of this article is to review the current guidelines and recommendations for percutaneous image-guided treatment of musculoskeletal tumors.

CONCLUSION

With the ongoing technologic advances, it is essential that the musculoskeletal interventionalist is familiar with the current tools and techniques available for the treatment of soft-tissue and bone tumors. Fortunately, many of these tools are readily available in a standard interventional radiology department and can be easily applied to the musculoskeletal system.

Advances in cryoablation for pancreatic cancer

Pancreatic carcinoma is a common cancer of the digestive system with a poor prognosis. It is characterized by insidious onset, rapid progression, a high degree of malignancy and early metastasis. At present, radical surgery is considered the only curative option for treatment, however, the majority of patients with pancreatic cancer are diagnosed too late to undergo surgery. The sensitivity of pancreatic cancer to chemotherapy or radiotherapy is also poor. As a result, there is no standard treatment for patients with advanced pancreatic cancer. Cryoablation is generally considered to be an effective palliative treatment for pancreatic cancer. It has the advantages of minimal invasion and improved targeting, and is potentially safe with less pain to the patients. It is especially suitable in patients with unresectable pancreatic cancer. However, our initial findings suggest that cryotherapy combined with 125-iodine seed implantation, immunotherapy or various other treatments for advanced pancreatic cancer can improve survival in patients with unresectable or metastatic pancreatic cancer. Although these findings require further in-depth study, the initial results are encouraging. This paper reviews the safety and efficacy of cryoablation, including combined approaches, in the treatment of pancreatic cancer.

A Vivens Ex Vivo Study on the Synergistic Effect of Electrolysis and Freezing on the Cell Nucleus

Freezing-cryosurgery, and electrolysis-electrochemical therapy (EChT), are two important minimally invasive surgery tissue ablation technologies. Despite major advantages they also have some disadvantages. Cryosurgery cannot induce cell death at high subzero freezing temperatures and requires multiple freeze thaw cycles, while EChT requires high concentrations of electrolytic products-which makes it a lengthy procedure. Based on the observation that freezing increases the concentration of solutes (including products of electrolysis) in the frozen region and permeabilizes the cell membrane to these products, this study examines the hypothesis that there could be a synergistic effect between freezing and electrolysis in their use together for tissue ablation. Using an animal model we refer to as vivens ex vivo, which may be of value in reducing the use of animals for experiments, combined with a Hematoxylin stain of the nucleus, we show that there are clinically relevant protocols in which the cell nucleus appears intact when electrolysis and freezing are used separately but is affected by certain combinations of electrolysis and freezing.

Mathematical study of probe arrangement and nanoparticle injection effects on heat transfer during cryosurgery

Blood vessels, especially large vessels have a greater thermal effect on freezing tissue during cryosurgery. Vascular networks act as heat sources in tissue, and cause failure in cryosurgery and reappearance of cancer. The aim of this study is to numerically simulate the effect of probe location and multiprobe on heat transfer distribution. Furthermore, the effect of nanoparticles injection is studied. It is shown that the small probes location near large blood vessels could help to reduce the necessary time for tissue freezing. Nanoparticles injection shows that the thermal effect of blood vessel in tissue is improved. Using Au, Ag and diamond nanoparticles have the most growth of ice ball during cryosurgery. However, polytetrafluoroethylene (PTFE) nanoparticle can be used to protect normal tissue around tumor cell due to its influence on reducing heat transfer in tissue. Introduction of Au, Ag and diamond nanoparticles combined with multicryoprobe in this model causes reduction of tissue average temperature about 50% compared to the one probe.

Thermal tumor ablation in clinical use

Although a surgical procedure is performed by visual inspection with histopathological assessment of the excised tumor and margins, percutaneous and noninvasive thermal ablation is performed strictly with the aid of imaging. Applicator guidance into the target zone, treatment monitoring and verification, and clinical follow-up rely on effective imaging. Detailed discussion of imaging is beyond the scope of this article, but the influence of imaging on the choice of thermal ablation or procedural approach will be discussed as needed. More information on imaging for interventional therapies can be found in other articles in this issue of IEEE Pulse.

An efficient thermal evolution model for cryoablation with arbitrary multi-cryoprobe configuration

Cryoablation has been demonstrated powerful in treating of a variety of diseases, especially for the tumor ablation, which destroys the target tissue through the controlled freezing of cryoprobe. The prediction of temperature evolution during cryoablation is of great importance for developing and improving clinical procedure. This paper presented an efficient thermal model to characterize the freezing effect of cryoprobe with arbitrary layout including its size, orientation and number. The key step of the presented model is to establish a boundary heat source method to implicitly characterize the heat transfer from cryoprobe with fixed temperature or convective heat transfer boundary condition, which is furthermore incorporated to a fast parallel alternating direction explicit (PADE) finite difference method for computation acceleration. A novel dynamical and conformal computational region is designed through the shortest distance definition to balance the thermal effect of tissue and computational efficiency. The detailed test cases including a real head tissue demonstrated that the current model can accurately predict the temperature field evolution induced by arbitrary multi-cryoprobe configuration, and achieve significant computational ability due to allowable large time step (100-fold compared with the explicit finite difference method), compact computational region (at least reducing 40% number of voxels) and high parallel efficiency (speedup ratio about 8 for 12 threads) for complex tissue structure.

Tolerability and effectiveness of liquid nitrogen spray cryotherapy with very short freeze times in the treatment of xanthelasma palpebrarum

Xanthelasma are cholesterol-filled, soft, yellow plaques that usually appear on the medial aspects of the eyelids bilaterally. They are always benign lesions so therapy is usually undertaken only for cosmetic reasons. Surgical excision, chemical peeling with tricholoroacetic acid, and laser ablation are commonly used treatments. Liquid nitrogen cryotherapy is a potentially effective but rarely used treatment due to the risk of intense eyelid swelling. We report on our experience with four of our patients, and propose an explanation for the effectiveness of gentle liquid nitrogen spray cryotherapy in xanthelasma. We consider that gentle liquid nitrogen cryotherapy should be used in the treatment of xanthelasma due to the ease of application and low risk of adverse effects.

Re-purposing cryoablation: a combinatorial 'therapy' for the destruction of tissue

It is now recognized that the tumor microenvironment creates a protective neo-tissue that isolates the tumor from the various defense strategies of the body. Evidence demonstrates that, with successive therapeutic attempts, cancer cells acquire resistance to individual treatment modalities. For example, exposure to cytotoxic drugs results in the survival of approximately 20-30% of the cancer cells as only dividing cells succumb to each toxic exposure. With follow-up treatments, each additional dose results in tumor-associated fibroblasts secreting surface-protective proteins, which enhance cancer cell resistance. Similar outcomes are reported following radiotherapy. These defensive strategies are indicative of evolved capabilities of cancer to assure successful tumor growth through well-established anti-tumor-protective adaptations. As such, successful cancer management requires the activation of multiple cellular 'kill switches' to prevent initiation of diverse protective adaptations. Thermal therapies are unique treatment modalities typically applied as monotherapies (without repetition) thereby denying cancer cells the opportunity to express defensive mutations. Further, the destructive mechanisms of action involved with cryoablation (CA) include both physical and molecular insults resulting in the disruption of multiple defensive strategies that are not cell cycle dependent and adds a damaging structural (physical) element. This review discusses the application and clinical outcomes of CA with an emphasis on the mechanisms of cell death induced by structural, metabolic, vascular and immune processes. The induction of diverse cell death cascades, resulting in the activation of apoptosis and necrosis, allows CA to be characterized as a combinatorial treatment modality. Our understanding of these mechanisms now supports adjunctive therapies that can augment cell death pathways.

Percutaneous cryoablation of ovarian cancer metastasis to the liver: initial experience in 13 patients

OBJECTIVE

To evaluate the feasibility, safety, and effectiveness of percutaneous cryoablation for the treatment of liver metastases from ovarian cancer.

METHODS/MATERIALS

A retrospective review was performed on 13 patients with liver metastases from ovarian cancer who underwent percutaneous cryoablation with computed tomography (CT) guidance. The tumor response was assessed by enhanced computed tomography performed before treatment, 1 month after, and every 3 months after treatment. The Functional Assessment of Cancer Therapy-General quality of life (QOL) was used to assess the patients' QOL before, 1 week, 1 month, and 3 months after cryoablation.

RESULTS

A total of 27 procedures of cryoablation were performed on these patients, and 5 patients underwent repeat procedures. Complete ablation was achieved for all lesions. Months are counted from the time of cryoablation, and the median duration of follow-up was 15 months (4-22 months). At the 1-month follow-up, the primary technique effectiveness was 100%. At the 3-month follow-up, local tumor progression was observed in 2 (7.14%) of 28 lesions. The 1-year survival from the time of cryoablation was 92.3%. Two patients died after 9 and 14 months, respectively. The QOL symptoms and functioning scales were preserved in patients alive at 3 months after cryoablation. No major complications such as cryoshock, hepatic bleeding, liver abscess, biliary fistula, and renal insufficiency were encountered.

CONCLUSIONS

Our initial experience showed that cryoablation is a safe and effective ablative therapy, providing a high rate of local tumor control in ovarian cancer liver metastases.

The Palm-Sized Cryoprobe System Based on Refrigerant Expansion and Boiling and Its Application to an Animal Model of Epilepsy

GOAL

The purpose of this study is to propose the palm-sized cryoprobe system based on a new concept and to suggest that the freezing technique could be used for treatment of epilepsy.

METHODS

We propose herein a cryoprobe system based on the boiling effect that uses a specific refrigerants with a boiling point higher than that of liquid nitrogen yet low enough to result in cell necrosis. To evaluate and verify the effectiveness of the proposed system, cooling characteristics are investigated in agar. In addition, the system is applied to a Wistar rat brain-model, in which the epileptic activities are induced in advance by a potent epileptogenic substance.

RESULTS

The design concept yielded the following benefits: 1) the selected refrigerant promotes sealing in the tank; 2) the tank can be made as compact as possible, limited only by the volume required for the refrigerant; 3) because the tank and probe units can be separated by a nonconducting, flexible, and high-pressure tube, the tank unit can be manipulated without disturbing the probe tip with mechanical vibrations and electrical noise. Although the agar experiments, we verified that the proposed system can uniquely and reproducibly create an ice ball. Moreover, in the rat experiments in vivo, it was confirmed that penicillin G-induced epileptic activities disappeared on freezing with the proposed system.

CONCLUSIONS

The palm-sized system has desired characteristics and can apply for an animal model of epilepsy.

SIGNIFICANCE

Results of in vivo experiments suggest that cryosurgery may be an effective treatment for epilepsy.

Simulation and evaluation of freeze-thaw cryoablation scenarios for the treatment of cardiac arrhythmias

Background

Cardiac cryoablation is a minimally invasive procedure to treat cardiac arrhythmias by cooling cardiac tissues responsible for the cardiac arrhythmia to freezing temperatures. Although cardiac cryoablation offers a gentler treatment than radiofrequency ablation, longer interventions and higher recurrence rates reduce the clinical acceptance of this technique. Computer models of ablation scenarios allow for a closer examination of temperature distributions in the myocardium and evaluation of specific effects of applied freeze-thaw protocols in a controlled environment.

Methods

In this work multiple intervention scenarios with two freeze-thaw cycles were simulated with varying durations and starting times of the interim thawing phase using a finite element model verified by in-vivo measurements and data from literature. To evaluate the effects of different protocols, transmural temperature distributions and iceball dimensions were compared over time. Cryoadhesion durations of the applicator were estimated in the interim thawing phase with varying thawing phase starting times. In addition, the increase of cooling rates was compared between the freezing phases, and the thawing rates of interim thawing phases were analyzed over transmural depth.

Results

It could be shown that the increase of cooling rate, the regions undergoing additional phase changes and depths of selected temperatures depend on the chosen ablation protocol. Only small differences of the estimated cryoadhesion duration were found for ablation scenarios with interim thawing phase start after 90 s freezing.

Conclusions

By the presented model a quantification of effects responsible for cell death is possible, allowing for the analysis and optimization of cryoablation scenarios which contribute to a higher clinical acceptance of cardiac cryoablation.

Spatial and Time-Course Thermodynamics During Pulmonary Vein Isolation Using the Second-Generation Cryoballoon in a Canine In Vivo Model

Background—

Thermodynamics in the left atrium–pulmonary vein (PV) junction, phrenic nerve, and esophagus during PV isolation (PVI) using the second-generation cryoballoon are not known.

Methods and Results—

Twenty dogs underwent PVI using second-generation cryoballoon. Ablations were performed for ≤2 deliveries based on PVI without a bonus freeze. Inner balloon, balloon surface, and tissue temperatures were monitored during cryoablation. The tissue thermocouples were placed on the epicardial surface of the left atrium–PV junction, as well as on the phrenic nerve and within the esophagus. A total of 259 cryoballoon and 229 tissue tissue thermocouples profiles during 53 cryoablations of 40 PVs were analyzed. Acutely, PVI was achieved in 36 of 40 PVs (90%). Conductive tissue cooling spread radially from the balloon–left atrium–PV contact point. The lowest tissue temperatures were dependent on the distance of the tissue thermocouples to the balloon surface ( r =0.85; P <0.001). In addition, blood flow leaks around the balloon had a warming effect on the balloon and tissue temperature profiles. Chronic isolation (mean, 48±16 days) was achieved in 27 of 36 PVs (75%). In 8 of 9 acutely isolated but with chronic reconnection PVs, the blood flow leak location was concordant with chronic reconnection gap. Although only 1 esophageal ulcerated lesion was observed, neither phrenic nerve palsy nor severe PV stenosis was seen in any dogs.

Conclusions—

Variance in tissue thermodynamics during cryothermal ablation depends on the distance from balloon and peri-balloon blood flow leaks. This information may be useful for successful PVI without severe complications.

Wallerian degeneration and recovery of motor nerves after multiple focused cold therapies

Introduction: A device has been developed to apply freezing temperatures to temporarily impede nerve conduction, resulting in inhibition of voluntary skeletal muscle contraction. This device was designed as an alternative to the neurotoxins usually used to treat movement disorders. Methods: We evaluated the effects of single and 3 repeat treatments with a cryoprobe device (−55°C) on a sciatic nerve rat model. Long-term effects of repeated treatment were evaluated through assessments of physiological function and histological analysis. Results: There was consistent weakening of physiological function after each treatment, with recovery of normal function by 8 weeks posttreatment. Histological findings showed axonal degeneration with no disruption to the epineurial or perineurial structures. Progressive axonal regeneration was followed by normal recovery by 24 weeks post-treatment. Conclusions: Low-temperature treatment of motor nerves did not result in permanent or long-term changes to nerve function or structure. Muscle Nerve 51: 268–275, 2015

Nonenzymatic Cryogenic Isolation of Therapeutic Cells: Novel Approach for Enzyme-Free Isolation of Pancreatic Islets Using In Situ Cryopreservation of Islets and Concurrent Selective Freeze Destruction of Acinar Tissue

Cell-based therapies, which all involve processes for procurement and reimplantation of living cells, currently rely upon expensive, inconsistent, and even toxic enzyme digestion processes. A prime example is the preparation of isolated pancreatic islets for the treatment of type 1 diabetes by transplantation. To avoid the inherent pitfalls of these enzymatic methods, we have conceptualized an alternative approach based on the hypothesis that cryobiological techniques can be used for differential freeze destruction of the pancreas (Px) to release islets that are selectively cryopreserved in situ. Pancreata were procured from juvenile pigs using approved procedures. The concept of cryoisolation is based on differential processing of the pancreas in five stages: 1) infiltrating islets in situ preferentially with a cryoprotectant (CPA) cocktail via antegrade perfusion of the major arteries; 2) retrograde ductal infusion of water to distend the acinar; 3) freezing the entire Px solid to lt; −160°C for storage in liquid nitrogen; 4) mechanically crushing and pulverizing the frozen Px into small fragments; 5) thawing the frozen fragments, filtering, and washing to remove the CPA. Finally, the filtered effluent (cryoisolate) was stained with dithizone for identification of intact islets and with Syto 13/PI for fluorescence viability testing and glucose-stimulated insulin release assessment. As predicted, the cryoisolate contained small fragments of residual tissue comprising an amorphous mass of acinar tissue with largely intact and viable (>90%) embedded islets. Islets were typically larger (range 50–500 μm diameter) than their counterparts isolated from juvenile pigs using conventional enzyme digestion techniques. Functionally, the islets from replicate cryoisolates responded to a glucose challenge with a mean stimulation index = 3.3 ± 0.7. An enzyme-free method of islet isolation relying on in situ cryopreservation of islets with simultaneous freeze destruction of acinar tissue is feasible and proposed as a new and novel method that avoids the problems associated with conventional collagenase digestion methods.

Current status of imaging-guided percutaneous ablation of breast cancer

OBJECTIVE

The purpose of this article is to briefly describe the various techniques used for percutaneous ablation of breast cancer, their preliminary results, and their limitations. The techniques include thermotherapy (radiofrequency ablation, laser irradiation, microwave irradiation, and insonation with high-intensity focused ultrasound waves), cryotherapy, and irreversible electroporation.

CONCLUSION

The techniques used for percutaneous ablation of breast cancer raise many questions and issues that must be addressed before percutaneous ablation can be adopted for the treatment of early breast cancer.

GLP-1 improves neuropathology after murine cold lesion brain trauma

OBJECTIVES

In this study, we address a gap in knowledge regarding the therapeutic potential of acute treatment with a glucagon-like peptide-1 (GLP-1) receptor agonist after severe brain trauma. Moreover, it remains still unknown whether GLP-1 treatment activates the protective, anti-neurodegenerative cAMP response element binding protein (CREB) pathway in the brain in vivo, and whether activation leads to observable increases in protective, anti-neurodegenerative proteins. Finally, we report the first use of a highly sensitive in vivo imaging agent to assess reactive species generation after brain trauma.

METHODS

Severe trauma was induced with a stereotactic cryo-lesion in mice and thereafter treated with vehicle, liraglutide, or liraglutide + GLP-1 receptor antagonist. A therapeutic window was established and lesion size post-trauma was determined. Reactive oxygen species were visualized in vivo and quantified directly ex vivo. Hematological analysis was performed over time. Necrotic and apoptotic tone and neuroinflammation was assessed over time. CREB activation and CREB-regulated cytoprotective proteins were assessed over time.

RESULTS

Lira treatment reduced lesion size by ∼50% through the GLP-1 receptor. Reactive species generation was reduced by ∼40-60%. Necrotic and apoptotic tone maintained similar to sham in diseased animals with Lira treatment. Phosphorylation of CREB was markedly increased by Lira in a GLP-1 receptor-dependent manner. CREB-regulated cytoprotective and anti-neurodegenerative proteins increased with Lira-driven CREB activation.

INTERPRETATION

These results show that Lira has potent effects after experimental trauma in mice and thus should be considered a candidate for critical care intervention post-injury. Moreover, activation of CREB in the brain by Lira - described for the first time to be dependent on pathology - should be investigated further as a potential mechanism of action in neurodegenerative disorders.

The feasibility of percutaneous renal cryoablation under local anaesthesia

OBJECTIVES

The aim of this study was to evaluate the feasibility of cryoablation of renal tumours without sedation.

MATERIALS AND METHODS

We prospectively evaluated 149 computed tomography-guided renal cryoablation procedures that were performed at our institution between 2009 and 2013. The patients received only 1 g of IV paracetamol prior to the procedure; intraprocedural, local anaesthesia was administered. We recorded the date and duration of the procedure, size and location of the tumour, number of cryoneedles used, need for dissection with saline or carbon dioxide and intraprocedural degree of pain, which was scored using an established visual analogue pain score (VAS) (0-10). Multivariate analysis was used to identify the associations between the recorded parameters and VAS.

RESULTS

An interventional radiologist and a technician could perform all procedures without the help of anaesthesiologists and with adequate analgesia. The pain level ranged from 0 to 8 (mean, 2.0). It did not correlate with the tumour size or with the number of cryoneedles. It was significantly greater when the ice ball involved renal cavities (p = .0033) and when carbon dioxide was used for dissection (p < .0001). Conversely, the team experience was positively correlated with lower pain levels (p = .0381).

CONCLUSION

This study demonstrates that the cryoablation of renal tumours is feasible by interventional radiologists alone using a combination of IV paracetamol and local anaesthesia.

Percutaneous Cryoablation for Liver Cancer

Based on the primary tumor site, liver cancer can be divided into two categories: (1) primary liver cancer and (2) metastatic cancer to the liver from a distant primary site. Guided cryoablation via many imaging methods induces iceball formation and tumor necrosisand is an attractive option for treating unresectable hepatocellular carcinoma (HCC) and metastatic liver cancer. There are several advantages to using cryoablation for the treatment of liver cancer: it can be performed percutaneously, intraoperatively, and laparoscopically; iceball formation can be monitored; it has little impact on nearby large blood vessels; and it induces a cryo-immunological response in situ. Clinically, primary research has shown that percutaneous cryoablation of liver cancer is relatively safe and efficient, and it can be combined with other methods, such as radiation therapy, chemotherapy, and immunology, to control disease. Although research is preliminary, cryosurgery is fast becoming an alternative treatment method for HCC or liver tumors. Here, we review the mechanisms of liver tumor cryoablation, cryoablation program selection, clinical efficiency, and complications following treatment.

[Advances in cryoballoon technology: benefits and risks in daily practice]

BACKGROUND

Cryoballoon ablation is nowadays a standard approach for pulmonary vein isolation in symptomatic atrial fibrillation. The second generation cryoballoon was introduced in 2012 and modifications and enhancement to the system promised a higher efficiency.

OBJECTIVES, MATERIALS AND METHODS

A comprehensive overview of advances in cryoballoon ablation is provided and the consequences for daily practice are described based on a PubMed literature search, taking into account own experiences.

RESULTS AND CONCLUSION

Advances in cryoballoon ablation result in a significantly higher efficiency. To maintain the overall safety of the procedure and to avoid phrenic nerve palsy and esophageal lesions, special care needs to be taken by following some safety aspects and cut-off criteria. More data are necessary to clarify if recommendations for cryoenergy titration with the new balloon are reasonable. Ongoing prospective studies comparing cryoballoon and radiofrequency (RF) ablation will give answers to the question which energy source is more favorable, and upcoming studies will evaluate the impact of cryoballoon ablation as a first line treatment option.

Cryosurgery for pancreatic cancer

The procedure of pancreatic cryosurgery is performed with intraoperative or percutaneous approaches. Based on current data and our initial experience, cryoablation appears to be a feasible, potentially safe and promising option in patients with locally advanced and unresectable pancreatic cancer. It is suggested that there are almost no known contraindications to the use of cryosurgery for pancreatic cancer. For most patients with pancreatic cancer, cryosurgery can substitute conventional surgery.

The application of cryoprobe therapy in orthopedic oncology

The cryoprobe is a relatively new surgical tool offering a more selective destruction of unwanted cells. Using expanded versions of basic thermodynamic formulas of conduction and convection, mathematical models are becoming more effective at mapping out the zone of destruction that can be expected when using cryoprobes. The development of this technology will allow for better surgical planning and postoperative care to decrease patient morbidity and mortality. It is thought that this invaluable tool will become increasingly prevalent in orthopedics.