Cryotherapy and radiofrequency ablation: pathophysiologic basis and laboratory studies

Nano-pulse stimulation™ therapy (NPS™) is superior to cryoablation in clearing murine melanoma tumors

Background

Nano-Pulse Stimulation™ Therapy (NPS™) is a new, bioelectric modality that applies ultrashort pulses of electric energy to trigger regulated cell death in treated tissues. Instead of initiating necrosis by heating or freezing, NPS therapy permeabilizes intracellular organelles to activate the cell's own self-destruct pathway of programmed or regulated cell death. Unlike cryotherapies that can both damage structural tissues and diffuse into the periphery beyond the margins of the lesion, NPS only affects cells within the treated zone leaving surrounding tissue and acellular components unaffected.

Methods

We generated melanoma tumors in mice by injecting B16-F10 cells intradermally and compared the efficacy and resulting skin damage from Nano-Pulse Stimulation Therapy with that of cryoablation in clearing these tumors.

Results

The results of the study demonstrate that NPS is superior at clearing B16-F10 melanoma lesions. NPS permanently eliminated up to 91% of all tumor lesions with a single treatment compared to cryoablation that only eliminated up to 66%. Importantly, NPS permanently eliminated these lesions with no recurrence and with minimal dermal fibrosis, underlying muscle atrophy, permanent hair follicle loss or other markers of permanent skin damage.

Conclusions

These findings suggest that NPS is a promising new modality for the clearance of melanoma tumors and is a more efficacious, less damaging approach than cryoablative methods for the treatment of aggressive malignant tumors.

MRI for in vivo Analysis of Ablation Zones Formed by Cooled Radiofrequency Neurotomy to Treat Chronic Joint Pain Across Multiple Axial Spine Sites

Purpose

Radiofrequency (RF) ablation is the targeted damage of neural tissues to disrupt pain transmission in sensory nerves using thermal energy generated in situ by an RF probe. The present study aims to evaluate the utility of magnetic resonance imaging (MRI) for in vivo quantitative assessment of ablation zones in human subjects following cooled radiofrequency neurotomy for chronic pain at spinal facet or sacroiliac joints. Ablation zone size and shape have been shown in animal models to be influenced by size and type of RF probe – with cooled RF probes typically forming larger, more spherical ablation zones. To date, MRI of RF ablation zones in humans has been limited to two single retrospective case reports.

Patients and Methods

A prospective, open-label pilot study of MRI for evaluation of cooled radiofrequency ablation zones following standard of care procedures in adult outpatients was conducted. Adult subjects (n=13) received monopolar cooled RF (CRF) ablation (COOLIEF™, Avanos Medical) of sensory nerves at spinal facet or sacroiliac joints, followed by an MRI 2–7 days after the procedure. MRI data were acquired using both Short Tau Inversion Recovery (STIR) and contrast-enhanced T1-weighted (T1C) protocols. T1C MRI was used to calculate 3-dimensional ellipsoid ablation zone volumes (V), where well-defined regions of signal hyperintensity were used to identify three orthogonal diameters (T, D, L) and apply the formula V=π/6×T×D×L.

Results

Among 13 patients, 96 CRF ablation zones were created at 4 different anatomic sites (sacroiliac, lumbar, thoracic and cervical). CRF ablation zone morphology varied by anatomical location and structural features of surrounding tissues. In some cases, proximity to bone and striations of surrounding musculature obscured ablation zone borders. The volumes of 75 of the 96 ablation zones were measurable from MRI, with values (mean±SD) ranging from 0.4679 (±0.29) cm³ to 2.735 (±2.62) cm³ for the cervical and thoracic sites, respectively.

Conclusion

In vivo T1C MRI analysis of cooled RF ablation zones at spinal facet and sacroiliac joints demonstrated variable effects of local tissues on ablation zone morphology. Placement of the CRFA probe very close to bone alters the ablation zone in a negative way, causing non-spherical and incomplete lesioning. These new data may serve to inform practicing physicians about optimal cooled RF probe placement in clinical procedures.

Novel ablation methods for treatment of gliomas

Primary brain tumors are among the deadliest cancers that remain highly incurable. A need exists for new approaches to tumor therapy that can circumvent the blood brain barrier (BBB), target highly resistant tumors and cancer stem-like cells (CSCs) as well create an anti-cancer immunomodulatory environment. Successful treatments may also require a combinatory approach utilizing surgery, chemotherapy, radiation and novel ablation strategies that can both eliminate the bulk tumor and prevent any potential residual CSCs from propagating in the resected tissue. A number of thermal and non-thermal ablation methods have been developed and tested, which have gained much enthusiasm for the treatment of brain tumors. Here we review the most common primary brain tumors and the candidate ablation methods for targeting the tumor and its microenvironment.

Percutaneous Image-Guided Cryoablation in Vascular Anomalies

Understanding and management of vascular anomalies has always been intriguing. These disorders exhibit an expected pattern of clinical presentation and progression, and characteristic imaging findings. Significant progress in understanding and treating patients with vascular anomalies has been made in the past quarter century. Newer multidisciplinary domains for treating these disorders with medical drugs and less invasive image-guided or surgical procedures are constantly evolving. Vascular anomalies can exhibit aggressive tumor-like behavior resulting in recurrence or persistent symptoms after treatment. Thermal ablation has been widely used in tumor treatment. This has generated interest on using thermal ablation for treating vascular anomalies. Percutaneous image-guided cryoablation is increasingly used for this purpose as compared with other ablation technologies. Availability of small caliber cryoprobes and the ability to monitor the freeze zone in real time have made this an attractive option to interventional radiologists. These experiences are relatively new and limited. It is helpful to understand the emerging role of this technology in the treatment of vascular anomalies.

Ablative Therapy for Small Renal Masses

The management of small renal masses has become an important public health topic. The increased use of cross-sectional imaging and ultrasound has led to a downward stage migration for the detection of small renal masses. Cancer-specific survival, however, has not reflected this trend accordingly. Although partial nephrectomy has been the mainstay of treatment of small renal masses less than 4 cm, there is growing interest in ablative therapies, such as cryoablation and radiofrequency ablation, due to decreased morbidity. Oncologic outcomes are limited by methodology and length of follow-up, but short-term recurrence rates are low.

Cryosurgery for Breast Cancer

As the majority of breast cancers present as small non-palpable lesions, alternatives for surgical lumpectomy come into consideration. Breast tumor ablation without surgical excision may be a less morbid procedure without sacrificing cancer control. Cryosurgery is one of several ablative options for the treatment of small unifocal breast cancer. The potential advantages include avoidance of a surgical procedure, less overall discomfort, improved cosmesis, quicker recovery and the prospect of overall cost benefits. Clinical experience in 29 patients is reviewed demonstrating effectiveness in properly chosen patients. A comparison of ablation methods is discussed. Finally, future research of the role of cryosurgery in the management of breast cancer is described.

Interventional oncology: pictorial review of post-ablation imaging of liver and renal tumors

Percutaneous image-guided ablation is now commonly performed in many institutions for the treatment of hepatocellular carcinoma, liver metastases, and renal cell carcinoma in select patients. Accurate interpretation of post-ablation imaging is of supreme importance because treatment algorithms for these diseases rely heavily on imaging to guide management decisions. The purpose of this pictorial essay is to provide abdominal imagers with a review of the indications for percutaneous ablation in the abdomen, a basic overview of ablation modalities in clinical use today, the expected post-ablation imaging findings in the liver and kidney, and potential complications of hepatic and renal ablation procedures.

Comparison of percutaneous ablation technologies in the treatment of malignant liver tumors

Tumor ablation is a minimally invasive technique used to deliver chemical, thermal, electrical, or ultrasonic damage to a specific focal tumor in an attempt to achieve substantial tumor destruction or complete eradication. As the technology continues to advance, several image-guided tumor ablations have emerged to effectively manage primary and secondary malignancies in the liver. Percutaneous chemical ablation is one of the oldest and most established techniques for treating small hepatocellular carcinomas. However, this technique has been largely replaced by newer modalities including radiofrequency ablation, microwave ablation, laser-induced interstitial thermotherapy, cryoablation, high-intensity-focused ultrasound ablation, and irreversible electroporation. Because there exist significant differences in underlying technological bases, understanding each mechanism of action is essential for achieving desirable outcomes. In this article, the authors review the current state of each ablation method including technological and clinical considerations.

Electrosurgery: part I. Basics and principles

The term electrosurgery (also called radiofrequency surgery) refers to the passage of high-frequency alternating electrical current through the tissue in order to achieve a specific surgical effect. Although the mechanism behind electrosurgery is not completely understood, heat production and thermal tissue damage is responsible for at least the majority--if not all--of the tissue effects in electrosurgery. Adjacent to the active electrode, tissue resistance to the passage of current converts electrical energy to heat. The only variable that determines the final tissue effects of a current is the depth and the rate at which heat is produced. Electrocoagulation occurs when tissue is heated below the boiling point and undergoes thermal denaturation. An additional slow increase in temperature leads to vaporization of the water content in the coagulated tissue and tissue drying, a process called desiccation. A sudden increase in tissue temperature above the boiling point causes rapid explosive vaporization of the water content in the tissue adjacent to the electrode, which leads to tissue fragmentation and cutting.

Review of the efficacy and safety of cryoablation for the treatment of small renal masses

PURPOSE

Small renal masses are increasingly being discovered incidentally on imaging for another reason. The standard of care of these masses involves excision by open or laparoscopic techniques. Recently, ablative techniques, such as radiofrequency ablation (RFA) and cryoablation, have taken a more prominent role in the treatment algorithm of these masses. We evaluate the effectiveness and safety of cryoablation to treat renal tumours.

METHODS

A review of the literature was conducted. There was no language restriction. Studies were obtained from the following sources: the Cochrane Library, PUBMED, EMBASE and LILACS.

RESULTS

There was no clinical trial identified in the literature. Thus, we described the results from 23 case series and retrospective studies with a reasonable sample size (number of reported patients in each study ≥30), with a total of 2104 analyzed tumours from 2038 patients. There was wide variability in the outcomes reported, but success rates were generally good. Follow-up was generally short, but some series reported outcomes at 5 years. The most common complications reported were hemorrhage (some of the patients requiring transfusion), perinephric hematoma and urine leaks.

CONCLUSION

Cryoablation presents a feasible treatment for patients with small renal masses. Only short-term data are available and, as such, meaningful conclusions regarding long-term cancer control cannot be made. More rigorous studies are needed.

Imaging after percutaneous radiofrequency ablation of hepatic tumors: Part 1, Normal findings

OBJECTIVE

The purpose of this article is to review the spectrum of early and delayed normal cross-sectional imaging findings after percutaneous radiofrequency ablation of hepatic tumors.

CONCLUSION

Knowledge of postablation imaging changes is vital not only for the interventionalist who performs the procedure but also for the diagnostician who interprets the postablation imaging. Recognition of normal postprocedural changes and differentiation from abnormal imaging findings prevent overcalling benign changes as abnormal and can thus avoid needless treatment.

Current status of ablative techniques for small renal masses

The past few decades have witnessed a steady increase in the number of newly diagnosed small renal masses. Although historically managed by surgical resection, many of these small renal masses are now noted to be amenable to less invasive treatment modalities including thermal ablation or active surveillance. Contemporary series suggest that renal thermal ablation (including cryoablation or radiofrequency ablation), when selectively employed, can maintain oncologic efficacy comparable to extirpation while minimizing complications and treatment morbidity. Therefore, as the incidence of small renal masses in elderly comorbid patients rises, it is likely we will see ablative techniques assume a greater role in management.

Nonthermal irreversible electroporation for intracranial surgical applications

Object

Nonthermal irreversible electroporation (NTIRE) is a novel, minimally invasive technique to treat cancer, which is unique because of its nonthermal mechanism of tumor ablation. This paper evaluates the safety of an NTIRE procedure to lesion normal canine brain tissue.

Methods

The NTIRE procedure involved placing electrodes into a targeted area of brain in 3 dogs and delivering a series of short and intense electric pulses. The voltages of the pulses applied were varied between dogs. Another dog was used as a sham control. One additional dog was treated at an extreme voltage to determine the upper safety limits of the procedure. Ultrasonography was used at the time of the procedure to determine if the lesions could be visualized intraoperatively. The volumes of ablated tissue were then estimated on postprocedure MR imaging. Histological brain sections were then analyzed to evaluate the lesions produced.

Results

The animals tolerated the procedure with no apparent complications except for the animal that was treated at the upper voltage limit. The lesion volume appeared to decrease with decreasing voltage of applied pulses. Histological examination revealed cell death within the treated volume with a submillimeter transition zone between necrotic and normal brain.

Conclusions

The authors' results reveal that NTIRE at selected voltages can be safely administered in normal canine brain and that the volume of ablated tissue correlates with the voltage of the applied pulses. This preliminary study is the first step toward using NTIRE as a brain cancer treatment.

Percutaneous computed tomography fluoroscopy–guided conformal ultrasonic ablation of vertebral tumors in a rabbit tumor model

Object

Radiofrequency ablation (RFA) has proven to be effective for treatment of malignant and benign tumors in numerous anatomical sites outside the spine. The major challenge of using RFA for spinal tumors is difficulty protecting the spinal cord and nerves from damage. However, conforming ultrasound energy to match the exact anatomy of the tumor may provide successful ablation in such sensitive locations. In a rabbit model of vertebral body tumor, the authors have successfully ablated tumors using an acoustic ablator placed percutaneously via computed tomography fluoroscopic (CTF) guidance.

Methods

Using CTF guidance, 12 adult male New Zealand White rabbits were injected with VX2 carcinoma cells in the lowest lumbar vertebral body. At 21 days, a bone biopsy needle was placed into the geographical center of the lesion, down which an acoustic ablator was inserted. Three multisensor thermocouple arrays were placed around the lesion to provide measurement of tissue temperature during ablation, at thermal doses ranging from 100 to 1,000,000 TEM (thermal equivalent minutes at 43°C), and tumor volumes were given a tumoricidal dose of acoustic energy. Animals were monitored for 24 hours and then sacrificed. Pathological specimens were obtained to determine the extent of tumor death and surrounding tissue damage. Measured temperature distributions were used to reconstruct volumetric doses of energy delivered to tumor tissue, and such data were correlated with pathological findings.

Results

All rabbits were successfully implanted with VX2 cells, leading to a grossly apparent spinal and paraspinal tissue mass. The CTF guidance provided accurate placement of the acoustic ablator in all tumors, as corroborated through gross and microscopic histology. Significant tumor death was noted in all specimens without collateral damage to nearby nerve tissue. Tissue destruction just beyond the margin of the tumor was noted in some but not all specimens. No neurological deficits occurred in response to ablation. Reconstruction of measured temperature data allowed accurate assessment of volumetric dose delivered to tissues.

Conclusions

Using a rabbit intravertebral tumor model, the authors have successfully delivered tumoricidal doses of acoustic energy via a therapeutic ultrasound ablation probe placed percutaneously with CTF guidance. The authors have thus established the first technical and preclinical feasibility study of controlled ultrasound ablation of spinal tumors in vivo.

Tumor ablation and nanotechnology

Next to surgical resection, tumor ablation is a commonly used intervention in the treatment of solid tumors. Tumor ablation methods include thermal therapies, photodynamic therapy, and reactive oxygen species (ROS) producing agents. Thermal therapies induce tumor cell death via thermal energy and include radiofrequency, microwave, high intensity focused ultrasound, and cryoablation. Photodynamic therapy and ROS producing agents cause increased oxidative stress in tumor cells leading to apoptosis. While these therapies are safe and viable alternatives when resection of malignancies is not feasible, they do have associated limitations that prevent their widespread use in clinical applications. To improve the efficacy of these treatments, nanoparticles are being studied in combination with nonsurgical ablation regimens. In addition to better thermal effect on tumor ablation, nanoparticles can deliver anticancer therapeutics that show a synergistic antitumor effect in the presence of heat and can also be imaged to achieve precision in therapy. Understanding the molecular mechanism of nanoparticle-mediated tumor ablation could further help engineer nanoparticles of appropriate composition and properties to synergize the ablation effect. This review aims to explore the various types of nonsurgical tumor ablation methods currently used in cancer treatment and potential improvements by nanotechnology applications.

The importance of nephron-sparing focal therapy: renal function preservation

Historically, renal cancer has been treated with radical nephrectomy. Consequently, many patients developed renal insufficiency and the health problems associated with this. With the increasing diagnosis of small renal masses, nephron-sparing treatments have been developed to treat these masses adequately, while maximizing renal function. Focal ablative therapy is a means to treat small renal masses in a minimally invasive manner. Yet, there are few studies that have focused on their ability to preserve renal function. In this article, we review the existing literature on the renal function outcomes of patients treated with either radio frequency ablation or cryoablation.

Cryoablation: mechanism of action and devices

Cryoablation refers to all methods of destroying tissue by freezing. Cryoablation causes cellular damage, death, and necrosis of tissues by direct mechanisms, which cause cold-induced injury to cells, and indirect mechanisms, which cause changes to the cellular microenvironment and impair tissue viability. Cellular injury, both indirect and direct, can be influenced by four factors: cooling rate, target temperature, time at target temperature, and thawing rate. In this review, the authors describe the mechanisms of cellular injury that occur with cryoablation, the major advantages and disadvantages of cryoablation compared with other thermal ablation techniques, and the current commercially available cryoablation ablation systems.

Renal ablative therapy: radiofrequency ablation and cryoablation

Widespread use of cross-sectional imaging has contributed to an increase in diagnosis of small renal masses. While extirpation has historically been the "gold standard" for managing such tumors, thermal ablation is increasingly utilized as primary surgical therapy. Contemporary series suggest that ablative procedures maintain oncologic outcomes similar to extirpation while minimizing patient morbidity. As more renal masses are diagnosed in elderly or comorbid patients, ablation will likely assume a central role in management strategies.

Current status of renal radiofrequency ablation

PURPOSE OF REVIEW

To provide an overview of the current literature addressing the role of radiofrequency ablation (RFA) for the management of renal cortical tumors.

RECENT FINDINGS

As the renal RFA experience continues to mature, longer-term data addressing the oncologic efficacy of this ablative modality are now available. Furthermore, the impact of RFA on secondary clinical endpoints, such as renal function outcomes, has now been addressed in several series.

SUMMARY

With the stage migration toward diagnosis of smaller renal masses, energy ablative techniques are being increasingly utilized as primary surgical modalities. Here, we review the role of RFA for the management of such masses and comment on technical considerations for this particular ablative technique. In addition, we provide a summary of contemporary longer-term oncologic outcomes and review the impact of RFA on renal function. As more renal masses are diagnosed in the elderly or comorbid patients, it is likely that ablative approaches will assume an increasingly central role in management strategies. In this regard, continued studies are necessary, particularly in regards to oncologic outcomes.

Cryoablation for small renal masses

Advances in imaging techniques (CT and MRI) and widespread use of imaging especially ultrasound scanning have resulted in a dramatic increase in the detection of small renal masses. While open partial nephrectomy is still the reference standard for the management of these small renal masses, its associated morbidity has encouraged clinicians to exploit the advancements in minimally invasive ablative techniques. The last decade has seen the rapid development of laparoscopic partial nephrectomy and novel ablative techniques such as, radiofrequency ablation (RFA), high-intensity focused ultrasound (HIFU), and cryoablation (CA). In particular, CA for small renal masses has gained popularity as it combines nephron-sparing surgery with a minimally invasive approach. Studies with up to 5-year followup have shown an overall and cancer-specific 5-year survival of 82% and 100%, respectively. This manuscript will focus on the principles and clinical applications of cryoablation of small renal masses, with detailed review of relevant literature.

CT and MR imaging after imaging-guided thermal ablation of renal neoplasms

In recent years, thermal tumor ablation techniques such as percutaneous radiofrequency (RF) ablation and cryoablation have assumed an important role in the management of renal tumors, particularly in patients who may be suboptimal candidates for more invasive surgical techniques. Postablation computed tomography (CT) and magnetic resonance (MR) imaging play an important part in evaluation of the ablation zone, surveillance for residual or recurrent tumor, and identification of procedure-related complications. The appearance of the ablation zone may vary depending on the ablation technique used, initial tumor size, and tumor location and composition. Most ablated tumors demonstrate a gradual decrease in size over time once the acute changes have resolved, although tumor involution is more evident after cryoablation than after RF ablation. Exophytic tumor ablation zones typically have a "bull's-eye" appearance on CT scans and MR images obtained after RF ablation, with a visible mass often persisting in the absence of viable tumor. Residual or recurrent tumor often manifests as a focus of nodular or crescentic enhancement on postablation contrast material-enhanced CT scans and MR images, although a thin peripheral rim of enhancement often persists for several months following cryoablation. Complications following renal tumor ablation are usually minor but may include hemorrhage, ureteral stricture, urine leak, colonic perforation and colonephric fistula, and pneumothorax. As more patients undergo renal ablation procedures, it will become increasingly important that radiologists be able to recognize typical postablation CT and MR imaging findings to prevent confusing them with other pathologic processes.

Histologic evaluation of radiofrequency ablation in renal cancer

AIM

To report on the histologic evaluation of renal tumors after intraoperative radiofrequency ablation (RFA) performed immediately before surgical nephrectomy.

MATERIALS AND METHODS

Ten patients with renal tumors were studied. All tumors were confirmed to be renal cell carcinoma before radio frequency ablation treatment. All specimens were stained with hematoxylin and eosin and nicotinamide adenine dinucleotide (NADH).

RESULTS

Mean tumor size was 29 mm (range 14 to 48 mm). Of the 10 tumors 5 were completely devitalized with a treatment margin ranged from 1 to 20mm. One tumor needed two treatment sessions. No complication related to radiofrequency treatment was recorded.

CONCLUSIONS

Our data indicate that RFA can completely destroy renal tumors. However, in our study, complete tumor cell death was obtained only in 50% of cases. More studies are needed to ensure that is technique is an effective and reproducible treatment.

Cryoablation of small peripheral renal masses: A retrospective analysis

Renal cryoablation is a minimally invasive, nephron-sparing option that has shown promise in the treatment of patients with solitary small renal lesions suspicious for malignancy. Few large clinical studies have used this promising technology, although intermediate-term data are encouraging. We present a retrospective review and report the outcomes of a large cohort of patients who underwent renal cryotherapy. Patients who were candidates for partial nephrectomy with peripheral lesions < or = 5.0 cm in maximum diameter and no history of bleeding disorders were offered cryoablation as definitive therapy. Two freeze-thaw cycles were used for all lesions, and all were characterized by intraoperative ultrasound immediately before freezing. Data were collected as part of standard care, and chart review was performed only in cases of missing data. From February 2001 to March 2005, 85 consecutive patients with an average age of 67 years and a mean tumor size of 2.6 cm (range, 1.2-4.7 cm; median, 2.5 cm), underwent renal cryoablation; 70 procedures were performed laparoscopically. Mean estimated blood loss was 58 mL, with 2 patients requiring transfusion. Mean hospital stay was 3.0 days (range, 0-14 days; median, 2 days) for the entire cohort and 2.2 days (range, 0-7 days; median, 2 days) for the laparoscopic group. A total of 7 laparoscopic cases were converted to an open approach early in the experience, 2 of which were considered technical failures. Mean follow-up was 10 months (range, 3-36 months). Abnormal postoperative enhancement occurred in 2 patients at 3 months and 12 months. Radical nephrectomy in the first revealed no viable tumor; needle biopsy in the second revealed renal cell carcinoma, which prompted nephrectomy. Intraoperative needle biopsy yielded a 59% malignancy rate. We conclude that renal cryotherapy is a viable option for nephron-sparing surgery in small, peripheral renal lesions. The procedure is well tolerated, may be considered in patients who are not good candidates for open surgical approaches, results in minimal morbidity, and has shown encouraging treatment results. Close posttreatment surveillance is essential. Longer-term follow-up data will be necessary if the long-term durability of renal cryotherapy is to be established.

[Laparoscopic assisted cryoablation of small renal masses]

AIMS

To review the current status of cryoablation of small renal masses and to preliminary report our experience at the AMC.

MATERIAL AND METHODS

A bibliographic search was conducted (PubMed/Medline/Embase) and the most important series were analyzed. Our series includes 13 patients with a solitary small renal mass treated by Laparoscopic assisted Cryoblation with fine cryoprobes (1,5 cm diameter). Postoperative follow-up was done by means of CT and/or MRI every three months during the first year and every 6 months during the second year.

RESULTS

There are no randomized trials comparing Cryoblation of renal masses (<4 cm diameter) with either radical surgery or partial nephrectomy but only case series. Complication rate is low as it is the recurrence or persistence rate in most of the series but one referring to radiologically guided Cryoablation (8%). The maximal diameter of the masses treated in our series were 3,2 cm. Tumors were approached retro or transperitoneally depending on their localization in the kidney. Average surgical time were 208 minutes (108-379) and average time of exposition to temperatures lower than -20 degrees C in the tumor periphery was 10 minutes. AT a mean follow-up of 8 months no tumoral recurrence were objectivated.

CONCLUSIONS

Cryoablation of small renal masses may be an acceptable alternative of treatment although mean follow-up is still short in all the series.

Percutaneous balloon cryoplasty: A new therapy for rapidly recurrent anastomotic venous stenoses of hemodialysis grafts?

Vascular access dysfunction is a major source of morbidity for end-stage renal disease patients on hemodialysis. The arteriovenous graft is a common access type for many of these patients. Frequent stenosis formation and thrombosis complicate this form of access. Patients may have a rapidly forming and recurrent venous stenosis at the graft-vein anastomosis that has been seen in both animal models and end-stage renal disease patients to be the result of neointimal hyperplasia. This venous lesion is particularly resistant and sometimes intractable to conventional angioplasty. As a result, new therapies have been developed to reduce the formation and/or recurrence of neointimal hyperplasia. These include special cutting balloons, drug-eluting stents, and endovascular brachytherapy. The authors present the cases of 5 patients with rapidly recurrent venous lesions at the graft-vein anastomosis that derived benefit from angioplasty with the cryoballoon. The time to stenosis or thrombosis in the arteriovenous grafts was increased from a mean of 3 weeks to more than 16 weeks with this technology. Cryotherapy with the cryoballoon (cryoplasty) may represent a useful therapy for patients with intractable stenoses at or near the venous anastomosis of arteriovenous grafts.