The emergent role of focal liver ablation techniques in the treatment of primary and secondary liver tumours

Magnetic Resonance Imaging-Guided Adaptive Radiotherapy for Colorectal Liver Metastases

Technological advances have enabled well tolerated and effective radiation treatment for small liver metastases. Stereotactic ablative radiation therapy (SABR) refers to ablative dose delivery (>100 Gy BED) in five fractions or fewer. For larger tumors, the safe delivery of SABR can be challenging due to a more limited volume of healthy normal liver parenchyma and the proximity of the tumor to radiosensitive organs such as the stomach, duodenum, and large intestine. In addition to stereotactic treatment delivery, controlling respiratory motion, the use of image guidance, adaptive planning and increasing the number of radiation fractions are sometimes necessary for the safe delivery of SABR in these situations. Magnetic Resonance (MR) image-guided adaptive radiation therapy (MRgART) is a new and rapidly evolving treatment paradigm. MR imaging before, during and after treatment delivery facilitates direct visualization of both the tumor target and the adjacent normal healthy organs as well as potential intrafraction motion. Real time MR imaging facilitates non-invasive tumor tracking and treatment gating. While daily adaptive re-planning permits treatment plans to be adjusted based on the anatomy of the day. MRgART therapy is a promising radiation technology advance that can overcome many of the challenges of liver SABR and may facilitate the safe tumor dose escalation of colorectal liver metastases.

External Beam Radiation Therapy for Liver Metastases

Stereotactic ablative radiotherapy (SABR) commonly is used for small liver metastases. Modern conformal radiotherapy techniques, including 3-dimensional conformal radiotherapy and intensity-modulated radiation therapy, enable the safe delivery of SABR to small liver volumes. For larger tumors, the safe delivery of SABR can be challenging due to a more limited volume of healthy normal liver parenchyma and the proximity of the tumor to radiosensitive organs, such as the stomach, duodenum, and large intestine. Controlling respiratory motion, the use of image guidance, and increasing the number of radiation fractions sometimes are necessary for the safe delivery of SABR in these situations.

Modeling liver electrical conductivity during hypertonic injection

Metastases in the liver frequently grow as scattered tumor nodules that neither can be removed by surgical resection nor focally ablated. Previously, we have proposed a novel technique based on irreversible electroporation that may be able to simultaneously treat all nodules in the liver while sparing healthy tissue. The proposed technique requires increasing the electrical conductivity of healthy liver by injecting a hypersaline solution through the portal vein. Aiming to assess the capability of increasing the global conductivity of the liver by means of hypersaline fluids, here, it is presented a mathematical model that estimates the NaCl distribution within the liver and the resulting conductivity change. The model fuses well-established compartmental pharmacokinetic models of the organ with saline injection models used for resuscitation treatments, and it considers changes in sinusoidal blood viscosity because of the hypertonicity of the solution. Here, it is also described a pilot experimental study in pigs in which different volumes of NaCl 20% (from 100 to 200 mL) were injected through the portal vein at different flow rates (from 53 to 171 mL/minute). The in vivo conductivity results fit those obtained by the model, both quantitatively and qualitatively, being able to predict the maximum conductivity with a 14.6% average relative error. The maximum conductivity value was 0.44 second/m, which corresponds to increasing 4 times the mean basal conductivity (0.11 second/m). The results suggest that the presented model is well suited for predicting on liver conductivity changes during hypertonic saline injection.

Resurrection of whole liver radiotherapy-A case report

INTRODUCTION

This is a case report of a patient of lymphoma with liver metastasis who had persistent pain and jaundice despite multiple lines of chemotherapy. She underwent palliative liver irradiation. This is an uncommon modality due to fear of radiation induced hepatitis. We reviewed literature available on the use of liver irradiation for palliation and concluded that it can be safely used with good results. A 33-year-old female with Non-Hodgkin's Lymphoma (NHL) presented with obstructive jaundice. She underwent stenting followed by chemotherapy. She was lost to follow up to later present with a progressively increasing right hypochondrial mass, pain and icterus. Ultrasound abdomen revealed massive hepatomegaly with hypodense lesions in both liver lobes and centring the porta with dilatation of biliary radicals. Despite multiple lines of chemotherapy and use of opioids, there was no symptomatic relief in pain, size of mass or any decrease in biochemical parameters. Then she was offered palliative radiation in the form of partial liver irradiation to a dose of 21Gy/7 fractions. She had >50% pain relief after 2 fractions and was off opioids by last fraction. Liver span reduced from 6cm to 1cm below costal margin in mid clavicular line. Radiologically 60% reduction in size of liver lesions was observed. Also, a decreasing trend in biochemical parameters was observed. Use of whole or partial liver irradiation is rare in clinical practice due to fear of radiation induced hepatitis by conventional techniques. Newer techniques of delivering radiation can highly improvise accuracy and permit further dose escalation.

Photoacoustic imaging driven by an interstitial irradiation source

Photoacoustic (PA) imaging has shown tremendous promise in providing valuable diagnostic and therapy-monitoring information in select clinical procedures. Many of these pursued applications, however, have been relatively superficial due to difficulties with delivering light deep into tissue. To address this limitation, this work investigates generating a PA image using an interstitial irradiation source with a clinical ultrasound (US) system, which was shown to yield improved PA signal quality at distances beyond 13 mm and to provide improved spectral fidelity. Additionally, interstitially driven multi-wavelength PA imaging was able to provide accurate spectra of gold nanoshells and deoxyhemoglobin in excised prostate and liver tissue, respectively, and allowed for clear visualization of a wire at 7 cm in excised liver. This work demonstrates the potential of using a local irradiation source to extend the depth capabilities of future PA imaging techniques for minimally invasive interventional radiology procedures.

Hepatocellular carcinoma: preclinical data on a dual-lumen catheter kit for fibrin sealant infusion following loco-regional treatments

BACKGROUND

Fibrin sealants are currently used in a variety of surgical and endoscopic settings to improve time to haemostasis, reduce blood loss and complications. However, the application of sealants (composed of two essential components: fibrinogen and thrombin) is not without difficulties. These sealants are normally applied to the resected area using dual-chamber delivery systems. Administration of these substances with different viscosities and diverse flow rates through a long catheter means that a certain amount of force needs to be applied and clot formation and clogging at the distal end of the catheter can occur.

METHODS

We designed a novel dual-lumen catheter to facilitate the optimal application of fibrin sealant after diagnostic and therapeutic percutaneous procedures and assessed the efficacy and tolerability of this dual-lumen kit when used in a model of hepatic fine needle aspiration (FNA) biopsy and radiofrequency ablation (RFA) in an in vivo, preclinical porcine study.

RESULTS

The experimental was performed on nine pigs (mean body weight 85 ± 7 kg) and with the exception of one pig, all animals survived in good conditions until the day of hepatectomy and euthanasia. The premature death of this animal was in the veterinarian's judgment caused by a common, non-infective disease. In all nine pigs, bleeding was stopped within 3 minutes of the application of the fibrin sealant and no cases of recurrent bleeding occurred.

CONCLUSIONS

The new dual aspect catheter increased ease of delivery of the sealant and FNA liver biopsy and RFA procedures were successfully and safely performed.

[Stereotactic body radiation therapy in the management of liver tumours]

Stereotactic radiotherapy is a high-precision technique based on the administration of high doses to a limited target volume. This treatment constitutes a therapeutic progress in the management of many tumours, especially hepatic ones. If surgery remains the standard local therapy, stereotactic radiotherapy is first dedicated to inoperable patients or unresectable tumours. Patients with moderately altered general status, preserved liver function and tumour lesions limited in number as in size are eligible to this technique. Results in terms of local control are satisfying, regarding primary tumours (notably hepatocellular carcinomas) as metastases stemming from various origins. If treatment protocols and follow-up modalities are not standardized to this day, iconographic acquisition using four-dimensional computed tomography, target volumes delineation based on morphological and/or metabolic data, and image-guided radiotherapy contribute to an oncologic efficacy and an improved sparing of the functional liver. The purpose of this literature review is to report the results of the main works having assessed stereotactic radiotherapy in the management of primary and secondary liver tumours. Technical particularities of this radiation modality will also be described.

Stereotactic body radiotherapy: a critical review for nonradiation oncologists

Stereotactic body radiotherapy (SBRT) involves the treatment of extracranial primary tumors or metastases with a few, high doses of ionizing radiation. In SBRT, tumor kill is maximized and dose to surrounding tissue is minimized, by precise and accurate delivery of multiple radiation beams to the target. This is particularly challenging, because extracranial lesions often move with respiration and are irregular in shape, requiring careful treatment planning and continual management of this motion and patient position during irradiation. This review presents the rationale, process workflow, and technology for the safe and effective administration of SBRT, as well as the indications, outcome, and limitations for this technique in the treatment of lung cancer, liver cancer, and metastatic disease.

CT-guided percutaneous microwave ablation of liver metastases from nasopharyngeal carcinoma

PURPOSE

To access efficacy of percutaneous microwave ablation (MWA) of liver metastases from nasopharyngeal carcinoma (NPC).

MATERIALS AND METHODS

From March 2007 to June 2012, 18 consecutive patients with NPC and liver metastases (15 men and three women; average age, 45.7 y; age range, 31-61 y) received computed tomography (CT)-guided percutaneous MWA treatment. A total of 27 ablations were performed involving 24 liver metastatic lesions in 18 patients with NPC. Average patient follow-up after ablation was 22.4 months (range, 2-52 mo). The average number of liver metastases per patient was 1.3 (range, 1-4 lesions), with lesion diameters ranging from 1.9 cm to 4.2 cm. Evaluation was then performed to assess percentage of complete necrosis, local tumor progression, and safety.

RESULTS

Technical success was achieved in all 27 MWA procedures performed. During follow-up, new metastatic lesions developed in four of 18 patients. Of these, two were liver metastases, and were successfully treated with repeat WMA. Only two major complications were observed: pneumothorax in a patient with an ablation pathway involving the thorax and postprocedural pain in two other patients. A median overall survival time of 41.4 months was observed (range, 2-50 mo); three of 18 patients died during follow-up.

CONCLUSIONS

CT-guided MWA is safe and offers an effective treatment alternative for local tumor control in selected patients with liver metastases from NPC.

Surgery for colorectal liver metastases

Half of all patients with colorectal cancer develop metastatic disease. The liver is the principal site for metastases, and surgical resection is the only modality that offers the potential for long-term cure. Appropriate patient selection for surgery and improvements in perioperative care have resulted in low morbidity and mortality rates, resulting in this being the therapy of choice for suitable patients. Modern management of colorectal liver metastases is multimodal incorporating open and laparoscopic surgery, ablative therapies such as radiofrequency ablation or microwave ablation and (neo)adjuvant chemotherapy. The majority of patients with hepatic metastases should be considered for resectional surgery, if all disease can be resected, as this offers the only opportunity for prolonged survival.

Combination of radiofrequency ablation and sequential cellular immunotherapy improves progression-free survival for patients with hepatocellular carcinoma

Hepatocellular carcinoma (HCC) recurs frequently after minimally invasive therapy. The aim of our study was to observe the efficiency and safety of the combined treatment of radiofrequency ablation (RFA) with cellular immunotherapy (CIT) for HCC patients. In our study, 62 patients with HCC who were treated with radical RFA were divided into two groups: RFA alone (32 patients) and RFA/CIT (30 patients). Autologous mononuclear cells were collected from the peripheral blood and separated by apheresis, and then induced into natural killer (NK) cells, γδT cells and cytokine-induced killer (CIK) cells. These cells were identified by flow cytometry with their specific antibodies and then were infused intravenously to RFA/CIT patients for three or six courses. The tumor recurrent status of these patients was evaluated with computed tomography or magnetic resonance imaging every 3 months after RFA. Progression-free survival (PFS), liver function, viral load and adverse effects were examined. The results implied that PFS was higher in RFA/CIT group than that in RFA group. In RFA/CIT group, six courses had better survival prognosis than three courses. Viral load of hepatitis C was decreased in two of three patients without antiviral therapy in RFA/CIT group, but was increased in RFA group. No significant adverse reaction was found in the patients with CIT. In summary, these preliminary results suggest that combination of sequential CIT with RFA for HCC patients was efficient and safe, and may be helpful in the prevention of the recurrence for the patients with HCC after RFA.

Mechanical disruption of tumors by iron particles and magnetic field application results in increased anti-tumor immune responses

The primary tumor represents a potential source of antigens for priming immune responses for disseminated disease. Current means of debulking tumors involves the use of cytoreductive conditioning that impairs immune cells or removal by surgery. We hypothesized that activation of the immune system could occur through the localized release of tumor antigens and induction of tumor death due to physical disruption of tumor architecture and destruction of the primary tumor in situ. This was accomplished by intratumor injection of magneto-rheological fluid (MRF) consisting of iron microparticles, in Balb/c mice bearing orthotopic 4T1 breast cancer, followed by local application of a magnetic field resulting in immediate coalescence of the particles, tumor cell death, slower growth of primary tumors as well as decreased tumor progression in distant sites and metastatic spread. This treatment was associated with increased activation of DCs in the draining lymph nodes and recruitment of both DCs and CD8(+)T cells to the tumor. The particles remained within the tumor and no toxicities were observed. The immune induction observed was significantly greater compared to cryoablation. Further anti-tumor effects were observed when MRF/magnet therapy was combined with systemic low dose immunotherapy. Thus, mechanical disruption of the primary tumor with MRF/magnetic field application represents a novel means to induce systemic immune activation in cancer.

Radiofrequency ablation in the treatment of liver metastases from colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is the most common malignant tumour and the third leading cause of cancer deaths in USA. For advanced CRC, the liver is the first site of metastatic disease; approximately 50 % of patients with CRC will develop liver metastases either synchronously or metachronously within 2 years after primary diagnosis. Hepatic resection (HR) is the only curative option, but only 15-20% of patients with liver metastases from CRC (CRLMs) are suitable for surgical standard treatment. In patients with unresectable CRLMs downsizing chemotherapy can improve resectability (16%). Modern systemic chemotherapy represents the only significant treatment for unresectable CRLMs. However several loco-regional treatments have been developed: hepatic arterial infusion (HAI), cryosurgical ablation (CSA), radiofrequency ablation (RFA), microwave ablation and selective internal radion treatment (SIRT). During the past decade RFA has superseded other ablative therapies, due to its low morbidity, mortality, safety and patient acceptability.

OBJECTIVES

The objective of this study was to systematically review the role of radiofrequency ablation (RFA) in the treatment of CRLMs.

SEARCH METHODS

We performed electronic searches in the following databases:CENTRAL, MEDLINE and EMBASE. Current trials were identified through the Internet using the Clinical-Trials.gov site (to January 2, 2012) and ASCO Proceedings. The reference lists of identified trials were reviewed for additional studies.

SELECTION CRITERIA

Randomized clinical trials (RCTs), quasi-randomised or controlled clinical trials (CCTs) comparing RFA to any other therapy for CRLMs were included. Observational study designs including comparative cohort studies comparing RFA to another intervention, single arm cohort studies or case control studies have been included if they have: prospectively collected data, ten or more patients; and have a mean or median follow-up time of 24 months. Patients with CRLMs who have no contraindications for RFA. Patients with unresectable extra-hepatic disease were also included.Trials have been considered regardless of language of origin.

DATA COLLECTION AND ANALYSIS

A total of 1144 records were identified through the above electronic searching. We included 18 studies: 10 observational studies, 7 Clinical Controlled Trials (CCTs) and an additional 1 Randomized Clinical Trial (RCT) (abstract) identified by hand searching in the 2010 ASCO Annual Meeting. The most appropriate way of summarizing time-to-event data is to use methods of survival analysis and express the intervention effect as a hazard ratio. In the included studies these outcome are mostly reported as dichotomous data so we should have asked authors research data for each participant and perform Individual Patient Data (IPD) meta-analysis. Given the study design and low quality of included studies we decided to give up and not to summarize these data.

MAIN RESULTS

Seventeen studies were not randomised and this increases the potential for selection bias. In addition, there was imbalance in the baseline characteristics of the participants included in all studies. All studies were classified as having a elevate risk of bias. The assessment of methodological quality of all non-randomized studies included in meta-analysis performed by the STROBE checklist has allowed us to identify several methodological limits in most of the analysed studies. At present, the information from the single RCT included (Ruers 2010) comes from an abstract of 2010 ASCO Annual Meeting where the allocation concealment was not reported; however in original protocol allocation concealment was adequately reported (EORTC 40004 protocol). The heterogeneity regarding interventions, comparisons and outcomes rendered the data not suitable.

AUTHORS' CONCLUSIONS

This systematic review gathers information from several controlled clinical trials and observational studies which are vulnerable to different types of bias. The imbalance between characteristics of patients in the allocated groups appears to be the main concern. Only one randomised clinical trial (published as an abstract), comparing 60 patients receiving RFA plus CT versus 59 patients receiving CT alone, was identified. This study showed that PFS was significantly higher in the group that received RFA. However, it was not able to provide information on overall survival. In conclusion, evidence from the included studies are insufficient to recommend RFA for a radical oncological treatment of CRLMs.

Evidence for tumor cell spread during local hepatic ablation of colorectal liver metastases

INTRODUCTION

The aim of the present study was to analyze the impact of cryosurgery (CRYO) on liver metastases compared to other thermoablative techniques. In a rat liver metastases model, evidence for tumor cell spread was analyzed comparing CRYO, radiofrequency ablation (RFA), and laser-induced thermotherapy (LITT).

METHODS

In an experimental study, we compared cell spillage in the washout of isolated perfused rat livers undergoing thermal ablation. Within the same model, CC531-GFP rat liver tumors were treated with CRYO, RFA, or LITT and the number of vital tumor cells within the perfusate was measured. Matrix metalloproteinases (MMP-2, MMP-9) were analyzed after in vivo ablation of rat colorectal liver metastases in the third experimental model.

RESULTS

Our data showed pronounced washout of cells after CRYO with a higher amount of intravascular cells and cell detritus compared to RFA and LITT. Only the effluent fluid of cryosurgery-treated livers revealed GFP-stained tumor cells. MMP-2 and MMP-9 expression was significantly higher after cryosurgery than after RFA and LITT.

CONCLUSION

When using thermoablative techniques, intravascular metastatic cell spillage is highest in CRYO, and increased expression of matrix metalloproteinases may further facilitate tumor cell spread. Therefore, RFA and LITT may be preferable whenever surgical resection of liver tumors is impossible.

Radiotherapy for liver metastases: a review of evidence

Over the past decade, there has been an increasing use of radiotherapy (RT) for the treatment of liver metastases. Most often, ablative doses are delivered to focal liver metastases with the goal of local control and ultimately improving survival. In contrast, low-dose whole-liver RT may be used for the palliation of symptomatic diffuse metastases. This review examines the available clinical data for both approaches. The review found that RT is effective both for local ablation of focal liver metastases and for palliation of patients with symptomatic liver metastases. However, there is a lack of a high level of evidence from randomized clinical trials.

Radiofrequency ablation or percutaneous ethanol injection for the treatment of liver tumors

The liver is a common location of both primary and secondary malignancies. For unresectable liver cancer, many local ablative therapies have been developed. These include e.g., percutaneous ethanol injection (PEI), percutaneous acetic acid injection, radiofrequency ablation (RFA), cryoablation, microwave ablation, laser-induced thermotherapy, and high-intensity focused ultrasound. RFA has recently gained interest and is the most widely applied thermoablative technique. RFA allows more effective tumor control in fewer treatment sessions compared with PEI, but with a higher rate of complications. However, there are certain circumstances where PEI therapy represents a better strategy to control liver tumors than RFA, especially in situations where RFA is difficult, for example when large vessels surround the tumor. In the context of hepatocellular carcinoma (HCC), both RFA and PEI are feasible and of benefit in non-operable patients. RFA seems superior to PEI in HCC > 2 cm, and the combination of interventions may be of benefit in selected patients. Liver resection is superior to RFA for patients with HCC meeting the Milan criteria, but RFA can be employed in tumors ≤ 3 cm and where there is an increased expected operative mortality. In addition, some lines of evidence indicate that RFA and PEI can be employed as a bridge to liver transplantation. The use of RFA in colorectal liver metastases is currently limited to unresectable disease and for patients unfit for surgery. The aim of this article is to summarize the current status of RFA in the management of liver tumors and compare it to the cheap and readily available technique of PEI.

Therapeutic potential of surgery for metastatic colorectal cancer

Evidence of the clinical benefit of surgery or metastasectomy for metastatic colorectal cancer to disease sites including the liver, lung, peritoneum, and pelvis as a potentially curative option is now available in the literature. The oncologic outcome of this treatment strategy achieves 5-year survival ranging between 20% and 50%. These survival gains have not been previously observed in the management of metastatic colorectal cancer. Treatment of potential surgical candidates requires a combined modality approach with systemic therapies to achieve macroscopic tumor removal and microscopic targeting of tumor deposits to achieve disease control. In nonsurgical candidates, systemic therapy, radiation therapy, and interventional oncology procedures may potentially facilitate sufficient disease downstaging for surgery. The purpose of this article is to provide a comprehensive review of the therapeutic advances in the surgical management of metastatic colorectal cancer.

Evolution from active surveillance to focal therapy in the management of prostate cancer

Organ-preserving therapies are widely accepted in many facets of medicine and, more recently, in oncology. For example, partial nephrectomy is now accepted as a preferred alternative over radical nephrectomy for small (up to 4 cm or T1) tumors. Focal therapy (FT) is another organ-preserving strategy applying energy (cryotherapy, laser ablation and/or high-intensity focused ultrasound) to destroy tumors while leaving the majority of the organ, surrounding tissue and structures unscathed and functional. Owing to the perceived multifocality of prostate cancer (PCa) technology limitations, in the past PCa was not considered suitable for FT. However, with the rise of active surveillance for the management of low-risk PCa in carefully selected patients, FT is emerging as an alternative. This is owing to technology improvements in imaging and energy-delivery systems to ablate tissue, as well as the realization that many men and clinicians still desire tumor control. With the postulated ability to ablate tumors with minimal morbidity, FT may have found a role in the management of PCa; the aim of FT a being long-term cancer control without the morbidity associated with radical therapies. Data for FT in PCa have been derived from case series and small Phase I trials, with larger cohort studies with longer follow-up having only just commenced. More data from large trials on the safety and efficacy of FT are required before this approach can be recommended in men with PCa. Importantly, studies must confirm that no viable cancer cells remain in the region of ablation. FT might eventually prove to be a ‘middle ground’ between active surveillance and radical treatment, combining minimal morbidity with cancer control and the potential for retreatment.

Ablative Technologies in the Management of Patients with Primary and Secondary Liver Cancer: An Overview

Interventional ablative technologies have played an increasingly important role in the management of patients with primary or secondary liver malignancies. Ethanol and acetic acid ablation were the primary modalities available 2 decades ago. Today, several new technologies are available, including radiofrequency ablation, cryoablation, and microwave ablation. Radiofrequency ablation is the most widely practiced, however, cryoablation and microwave ablation are reasonable choices in certain situations. Irreversible electroporation is a newer technique, which has yet to enter clinical practice, but shows promising preliminary results. Herein, we provide a brief overview of the above-mentioned technologies with a focus on principles of ablation and technique. We also describe the use of these techniques in the context of cytoreduction, a noncurative approach aimed at reducing the overall tumour burden and providing concomitant survival benefit.

Focal therapy in prostate cancer: modalities, findings and future considerations

Focal therapy is emerging as an alternative to active surveillance for the management of low-risk prostate cancer in carefully selected patients. The aim of focal therapy is long-term cancer control without the associated morbidity that plagues all radical therapies. Different energy modalities have been used to focally ablate cancer tissue, and available techniques include cryotherapy, laser ablation, high-intensity focused ultrasound and photodynamic therapy. The majority of evidence for focal therapy has come from case series and small phase I trials, and larger cohort studies with longer follow-up are only now being commenced. More data from large trials on the safety and efficacy of focal therapy are therefore required before this approach can be recommended in men with prostate cancer; in particular, studies must confirm that no viable cells remain in the region of ablation. Focal therapy might eventually prove to be a 'middle ground' between active surveillance and radical treatment, combining minimal morbidity with cancer control and the potential for re-treatment.

Radiofrequency ablation of unresectable liver tumors: factors associated with incomplete ablation or local recurrence

BACKGROUND

Radiofrequency ablation (RFA) of liver tumors is associated with a risk of incomplete ablation or local recurrence.

METHODS

One hundred sixty-eight patients with 311 unresectable liver tumors were included. Effects of different variables on incomplete ablation and local recurrence were analyzed.

RESULTS

There were 132 hepatocellular carcinomas and 179 liver metastases. Tumor size was 24 (±13) mm. Two hundred twenty-six tumors were treated percutaneously, and 85 through open approach (associated with liver resection in 42 cases). There was no mortality. Major morbidity rate was 7%. Incomplete ablation and local recurrence rates were 14% and 18.6%. Follow-up was 29 months. On multivariate analysis, factors associated with incomplete ablation were tumor size (>30 mm vs ≤30 mm, P = .004) and approach (percutaneous vs open, P = .0001). Factors associated with local recurrence were tumor size (>30 mm vs ≤30 mm, P = .02) and patient age (>65 years vs ≤65 years, P = .05).

CONCLUSIONS

RFA is effective to treat unresectable liver tumors. However, there is a risk of incomplete ablation when percutaneously treating tumors >30 mm. When tumor ablation is completely achieved, the main factor associated with local recurrence is tumor size >30 mm.

Intratumoural GM-CSF microspheres and CTLA-4 blockade enhance the antitumour immunity induced by thermal ablation in a subcutaneous murine hepatoma model

PURPOSE

We evaluated the effect of a new antitumour immunity regimen that included microwave ablation, intratumoural microspheres encapsulating granulocyte-macrophage colony stimulating factor (GM-CSF), and blockade of cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4).

MATERIALS AND METHODS

C57BL6 mice with an established subcutaneous Hepa 1-6 hepatoma underwent microwave ablation, followed by intratumoural injection of GM-CSF microspheres, and intraperitoneal injection of anti-CTLA-4 antibodies. The therapeutic effects were evaluated by tumour growth, survival analysis, and cytotoxicity of T lymphocytes against Hepa 1-6.

RESULTS

The co-administration of microwave thermal ablation, GM-CSF microspheres, and anti-CTLA-4 rejected tumour rechallenge in 90% of treated mice in a subcutaneous murine Hepa 1-6 model, and cured established distant tumour in 50% of the treated mice. This antitumour immune response was tumour-specific and mediated by natural killer (NK), CD4+, and CD8+ T cells.

CONCLUSIONS

Microwave ablation, followed by intratumoural GM-CSF microspheres, and anti-CTLA-4 antibodies results in the local eradication of tumours, rejection of tumours following rechallenge, and cures established distant tumours, suggesting that this is a promising regimen and one that is readily applicable in the clinic.

Liver ablation techniques: a review

BACKGROUND

Ablation techniques for unresectable liver carcinomas have evolved immensely since their introduction. Results of studies involving these techniques are restricted to reports of patient case series, which are often not presented in a standardised manner. This review aims to summarise the major studies in ablation technologies and present them in a way that may make comparison between the major modalities easier.

METHODS

All major databases (Medline, Cochrane, Embase and Pubmed) were searched for studies using microwave, radiofrequency or cryoablation to treat unresectable liver tumours. Only studies with at least 30 patients and 3-year follow-up were included. Complication, recurrence and survival rates of all studies are summarised and presented.

RESULTS AND CONCLUSION

It is difficult to compare ablation modalities, as probe design and energy sources have evolved rapidly over the last decade. Ablation offers an invaluable palliative option and in some cases it may offer rates of cure approaching that of surgical resection with lower morbidity and mortality. Perhaps the time has come, therefore, for prospective large-scale randomised control trials to take place comparing ablation modalities to each other and surgical resection.

Radiofrequency ablation induces antigen-presenting cell infiltration and amplification of weak tumor-induced immunity

PURPOSE

To evaluate the influence of subtotal radiofrequency (RF) ablation on a tumor-specific immune response in a murine tumor model and to explore the role of intratumoral dendritic cells (ITDCs) in mediating this effect.

MATERIALS AND METHODS

Animal work was performed according to an approved protocol and in compliance with the National Cancer Institute Animal Care and Use Committee guidelines and regulations. A murine urothelial carcinoma (MB49) model expressing the male minor histocompatibility (HY) antigen was inoculated subcutaneously in female mice. Fourteen days later, splenic T cells were analyzed with enzyme-linked immunosorbent spot for HY immune response (n = 57). In subsequent experiments, mice were randomized into control (n = 7), RF ablation, ITDC (n = 9), and RF ablation + ITDC (n = 9) groups and monitored for tumor growth. Eleven days after treatment, tumors were harvested for histologic and immunohistochemical analysis. Animals demonstrating complete tumor regression were rechallenged in the contralateral flank.

RESULTS

Animals treated with subtotal RF ablation showed significant increases in tumor-specific class I and II responses to HY antigens and tumor regression. RF ablation, ITDC, and combined groups demonstrated similar levels of antigen-presenting cell infiltration; all groups demonstrated greater levels of infiltration compared with untreated controls. ITDC injection also resulted in tumor regression. However, combination therapy did not enhance tumor regression when compared with either treatment alone. Rechallenged mice in RF ablation, ITDC, and combination groups demonstrated significant tumor growth inhibition compared with controls.

CONCLUSION

Subtotal RF ablation treatment results in enhanced systemic antitumor T-cell immune responses and tumor regression that is associated with increased dendritic cell infiltration. ITDC injection mimics the RF ablation effect but does not increase immune responses when injected immediately after RF ablation.

High-intensity focused ultrasound ablation for the treatment of colorectal liver metastases during an open procedure: study on the pig

OBJECTIVE

To demonstrate in a porcine model that high-intensity focused ultrasound (HIFU) with toroid-shaped emitters may have a role in treating unresectable colorectal liver metastases.

SUMMARY BACKGROUND DATA

Surgical resection is the only curative option for colorectal hepatic metastases. Only 20% of patients are suitable for surgery. Many ablative techniques have been assessed but several limitations have been documented: traumatic puncture of the parenchyma, limited size of lesions, and inability to monitor the treatment in real time.

METHODS

A HIFU device with 256 toroid-shaped emitters and integrated ultrasound imaging probe was used. Single lesions, induced in 40 seconds, and juxtaposition of 6 single lesions were created under ultrasound guidance on 13 pigs. The lesions were studied on sonograms, macroscopically and microscopically up to 30 days after the treatment.

RESULTS

Ninety percent of the HIFU lesions were immediately hypoechoic on ultrasound imaging. The average coagulated volume obtained from a 40 seconds total exposure in the liver was 7.0 +/- 2.5 cm (1.5-20.0), average diameter: 19.5 +/- 3.8 mm (10.0-29.0). Using the real-time visualization of the treated region, single lesions were easily juxtaposed to produce larger lesions up to 6 cm in diameter without any major complication.

CONCLUSIONS

This toroid HIFU device allows short treatment times, noninvasiveness regarding the liver and real time ultrasound guidance. It seems to be simpler and more reliable to use than current ablative methods. Additionally, lesions through large vessels (up to 5 mm) being feasible, treatment of some juxta-vascular metastases should be possible.

Percutaneous radiofrequency ablation for treatment of hepatoblastoma recurrence

Radiofrequency ablation (RFA) has been widely reported as a minimally invasive treatment for liver tumours in adults, but has not been documented as a treatment for hepatoblastoma in a child. We report a 2-year-old boy with local recurrence of hepatoblastoma after partial hepatectomy. Percutaneous RFA was performed under real-time sonographic guidance. There was no imaging evidence of recurrence after a follow-up of 2 years. We consider this a promising technique in children.

Surgical resection versus radiofrequency ablation in the treatment of small unifocal hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) has a high worldwide prevalence and mortality. While surgical resection and transplantation offers curative potential, donor availability and patient liver status and comorbidities may disallow either. Interventional radiological techniques such as radiofrequency ablation (RFA) may offer acceptable overall and disease-free survival rates.

MATERIALS AND METHODS

Sixty-eight cirrhotic patients matched for age, sex, tumor size, and Child-Pugh grade with small (1-5 cm) unifocal HCC were studied retrospectively to find determinants of overall and disease-free survival in those treated with surgical resection and RFA between 1991 and 2003.

RESULTS

Multivariate analysis using Cox proportional regression modeling showed that overall survival was related to tumor recurrence (p = 0.010), tumor diameter (p = 0.002), and treatment modality (p = 0.014); overall p = 0.008. Recurrence was independently related to the use of RFA over surgery (p = 0.023) on multivariate analysis; overall p = 0.034.

CONCLUSION

Surgical resection offers longer disease-free survival and potentially longer overall survival than RFA in patients with small unifocal HCC.

Cost of radiofrequency ablation in the treatment of hepatic malignancies

OBJECTIVES

Our primary objective was to assess the cost of radio-frequency ablation (RFA) of hepatic malignancies and to compare it to hospital reimbursement paid in the French Prospective Payment System (PPS).

PATIENTS AND METHODS

A series of 305 patients were enrolled into a prospective study. All resources used during the RFA-related hospital stay were recorded. Costs were assessed from the perspective of the health care providers and computed for four groups of patients: percutaneous RFA in an outpatient setting (group Ia, N=44), percutaneous RFA in an inpatient setting (group Ib, N=94), laparoscopic RFA (group II, N=44) and intraoperative RFA combined with resection (group III, N=120).

RESULTS

Mean hospital costs were estimated at euro 1581 (group Ia), euro 3824 (group Ib), euro 8194 (group II) and euro 12967 (group III). Costs per stay without intensive care in these groups were respectively euro 1581, euro 3635, euro 6622 and euro 10905 and reimbursement (intensive care excluded) was euro 560, euro 3367, euro 9084 and euro 11780.

CONCLUSION

In the French PPS, the cost of RFA is covered by lump sums paid to hospitals exclusively for intraoperative and laparoscopic RFA. For percutaneous RFA, which is the most frequent approach, reimbursement is highly insufficient.

Toric HIFU transducer for large thermal ablation

A new geometry of High Intensity Focused Ultrasound (HIFU) transducer is described to enlarge the coagulated volume and decrease treatments time. Eight transducer elements and their quarter-wave plate were diced out of a single toric piezocomposite element. Each transducer operates at a frequency of 3 MHz. The focal zone is conic and located at 70 mm from the transducer. A 7.5 MHz ultrasound imaging probe is placed in the centre of the device for guiding the treatment. Optimal exposure parameters were determined from numerical simulations. This new geometry allows achieving a thermal ablation of 7.5 cm3 when each of the eight transducers has performed a 5-s ultrasound exposure alternatively and consecutively. In vivo trials have been performed on five pigs to demonstrate this new principle. 33 elementary lesions have been performed. All lesions were reproducible and homogeneous. The average diameter of an elementary lesion obtained in 40 seconds was 19.5 +/- 3.8 mm (min 10 - max 29 mm). The coagulated volume obtained in 40 seconds was on average 9.1 +/- 4.6 cm3 (min 1.5 - max 17.6 cm3).

Multiple-electrode radiofrequency ablation of in vivo porcine liver: comparative studies of consecutive monopolar, switching monopolar versus multipolar modes

PURPOSE

To evaluate the in vivo efficiency of 2 multiple-electrode radiofrequency (RF) systems to create confluent areas of coagulation in porcine liver, compared with consecutive overlapping ablation.

MATERIALS AND METHODS

A total of 18 coagulations were created with 3 RF devices and 3 internally cooled electrodes at laparotomy in 6 female pigs. RF was applied to the porcine livers in a consecutive, monopolar mode (group A), in a switching monopolar mode (group B), or in a multipolar mode (group C). Energy efficiency values for the RF systems, shape and dimensions, and the coefficients of variation of the coagulation zones were compared in the 3 groups.

RESULTS

The duration of the RF ablation procedures in groups A, B, and C were 36 minutes, 18 minutes, and 21.2 +/- 1.9 minutes. The average energy delivered to produce 1 cm(3) coagulation was greater in group A (5.6 +/- 2.3 kJ/cm(3)) than in group B (1.8 +/- 0.5 kJ/cm(3)) or in group C (2.0 +/- 0.8 kJ/cm(3)) (P < 0.05). The mean volumes of the coagulations in groups A, B, and C were 28.8 +/- 13.2 cm(3) in group A, 49.1 +/- 12.3 cm(3) in group B, and 40.6 +/- 16.3 cm(3) in group C, respectively (P = 0.07). Regarding the shape of the coagulations, the coagulations of groups B (isoperimetric ratio; 0.88) and C (0.84) were more spherical than those of group A (0.69) (P < 0.05). In addition, the coefficients of variation of the volumes of the ablation zones in groups A, B, and C were 0.46, 0.25, and 0.40, respectively.

CONCLUSIONS

Multiple-electrode RF systems in switching monopolar and multipolar modes more efficiently created a larger, confluent, spherical-shaped coagulation than conventional consecutive RF ablation.

Developing an interstitial ultrasound applicator for thermal ablation in liver: results of animal experiments

BACKGROUND

In this project, an interstitial ultrasound applicator was developed for the treatment of primary and secondary cancers of the liver. Experiments on animals were used to check the destructive capabilities of this probe within the hepatic parenchyma of the pig in vivo, with a study of the physical parameters of the ultrasound treatment. In parallel, the possibility of visualizing the lesions induced by means of ultrasound imaging was also studied.

MATERIALS AND METHODS

Thirteen pigs were used in this project, which had received the prior approval of the ethics committee of Lyon Veterinary School. Ultrasound lesions were performed by varying the physical parameters of the treatment (acoustic intensity and shot time) with the aim of obtaining larger and larger areas of destruction. An operative device was developed to ensure precision in treatments. Two types of lesions were performed: elementary lesions corresponding to single shots at 40 degrees to 50 degrees rotation intervals, and cylindrical lesions obtained by a continuous rotary deployment of the probe. The effect of hepatic pedicle clamping on the size of ultrasound lesions was studied. The aspect and dimension of the lesions were analyzed by means of operative ultrasound imaging and macroscopic examination. Histological analysis showed the impact of the treatment on the hepatic parenchyma.

RESULTS

This work made it possible to study the elementary ultrasound lesions produced by our probe. Seventy elementary ultrasound lesions were analyzed. Treatments could be performed on all pigs without any difficulty. There were no operative incidents. The ultrasound-induced elementary lesions showed complete necrosis, with lesion length of up to 37 mm obtained without resort to pedicle clamping; this must be considered as a radius of the final lesion obtained over a complete rotary deployment (360 degrees ), then a diameter of 7 cm of thermal ablation can theoretically be obtained. The effect of pedicle clamping was studied and showed improvement of the lesion length. Results of continuous rotary deployment of the probe were encouraging. Operative ultrasound imaging proved to be a simple tool for directing and positioning the applicator in the target zone on the one hand and which, on the other hand, enabled accurate, real-time visualization of the ultrasound lesions. On histological analysis, the ultrasound-induced necrosis was complete and well defined.

CONCLUSION

This work shows that it is feasible to treat cancers of the liver using interstitial ultrasound probe. Thermal damage obtained on the hepatic parenchyma of pigs in vivo is complete and can be monitored using simple diagnostic ultrasound. The ultrasound parameters can be adapted to obtain destruction of variable size.

The safety of radiofrequency thermal ablation in the treatment of liver malignancies

INTRODUCTION

Radiofrequency ablation (RFA) has become widely accepted as an important adjunct, and sometimes a viable alternative, to liver surgery. The aims of this study are to assess the risks associated with percutaneous RFA and to discuss the indications and contraindications to its use.

PATIENTS AND METHODS

This is a review of 130 consecutive patients who were treated for primary (n = 92) and metastatic (n = 38) liver tumours. Only complications after percutaneous RFA (83 patients) were evaluated. Interesting case studies are included to highlight potential complications following RFA and their management.

RESULTS

One patient died of perforation of the colon and five others had major complications. There were 15 minor complications. Local recurrence rates reached 30% overall, and a further 25 patients developed a new hepatic lesion, different from the one treated by RFA. Median disease-free survival was 13 months. Overall survival rates at 1, 2 and 5 years were 85.3%, 71.3% and 57.6%, respectively.

CONCLUSION

Percutaneous RFA is a safe and efficient technique but not free of complications and with potential fatal outcome. It is also associated with significant local recurrence rates. The procedure should only be performed following adequate training and the indication should always be discussed in multidisciplinary meetings. Patient's liver function and general health as well as tumour size and position must be considered. Intraoperative or video laparoscopic RFA is useful for superficial tumours in order to avoid damage to viscera surrounding the liver surface.

Dielectric properties of human normal, malignant and cirrhotic liver tissue: in vivo and ex vivo measurements from 0.5 to 20 GHz using a precision open-ended coaxial probe

Hepatic malignancies have historically been treated with surgical resection. Due to the shortcomings of this technique, there is interest in other, less invasive, treatment modalities, such as microwave hepatic ablation. Crucial to the development of this technique is the accurate knowledge of the dielectric properties of human liver tissue at microwave frequencies. To this end, we characterized the dielectric properties of in vivo and ex vivo normal, malignant and cirrhotic human liver tissues from 0.5 to 20 GHz. Analysis of our data at 915 MHz and 2.45 GHz indicates that the dielectric properties of ex vivo malignant liver tissue are 19 to 30% higher than normal tissue. The differences in the dielectric properties of in vivo malignant and normal liver tissue are not statistically significant (with the exception of effective conductivity at 915 MHz, where malignant tissue properties are 16% higher than normal). Also, the dielectric properties of in vivo normal liver tissue at 915 MHz and 2.45 GHz are 16 to 43% higher than ex vivo. No statistically significant differences were found between the dielectric properties of in vivo and ex vivo malignant tissue (with the exception of effective conductivity at 915 MHz, where malignant tissue properties are 28% higher than normal). We report the one-pole Cole-Cole parameters for ex vivo normal, malignant and cirrhotic liver tissue in this frequency range. We observe that wideband dielectric properties of in vivo liver tissue are different from the wideband dielectric properties of ex vivo liver tissue, and that the in vivo data cannot be represented in terms of a Cole-Cole model. Further work is needed to uncover the mechanisms responsible for the observed wideband trends in the in vivo liver data.

Proof of concept percutaneous treatment system to enable fast and finely controlled ablation of biological tissue

A prototype system has been developed for producing controllable ablation of spherical lesions with a diameter of up to 2 cm. The system is based on a solid-state energy source operating in the super high frequency (SHF is defined as being a frequency of between 3 and 30 GHz) region of the electromagnetic spectrum. Results obtained from preliminary tissue testing, performed on morbid tissue samples prepared in a laboratory environment, show repeatability in terms of shape and size of ablation, and demonstrate the ability to produce controlled ablation in morbid liver and kidney models.

Quality of life after radiofrequency ablation combined with transcatheter arterial chemoembolization for hepatocellular carcinoma: comparison with transcatheter arterial chemoembolization alone

OBJECTIVE

Comprehensive studies are scarce with regard to the quality of life (QOL) of hepatocellular carcinoma (HCC) patients after transcatheter arterial chemoembolization (TACE) and/or radiofrequency ablation (RFA) treatment. The purpose of this study was to examine the impact of TACE alone and that of the TACE followed by RFA (TACE-RFA) on QOL in HCC patients.

METHODS

QOL was measured using the Functional Assessment of Cancer Therapy-General (FACT-G) (Version 4.0) questionnaire, translated into Chinese, as a measure of QOL among Chinese HCC patients. Prospectively, 83 patients in both TACE group (n = 40) and TACE-RFA group (n = 43) completed the questionnaire at baseline and 3 months after treatment, respectively.

RESULTS

The TACE-RFA group resulted in a significantly higher total QOL score, socio-family well-being score, and functional well-being score than that of TACE group, 3 months after respective treatment. Liver function, tumor recurrence and complication, age, income were the most important factors affecting the QOL of HCC patients after treatment. The logistic regression analyses showed that Child-Pugh Class and tumor recurrence after treatment were independent predictors of post-treatment QOL scores of HCC patients.

CONCLUSIONS

The overall QOL of HCC patients in TACE-RFA group was maintained at a relatively higher level than that of TACE group. TACE followed by RFA appeared to be more favorable than TACE alone with respect to QOL.

Combined radiofrequency ablation and doxorubicin-eluting polymer implants for liver cancer treatment

Previously, biodegradable polymer implants (polymer millirods) to release chemotherapeutic agents directly into tumors have been developed. The purpose of this study is to evaluate local drug distribution from these implants in liver tumors treated with radiofrequency (RF) ablation and determine if the implants provide a therapeutic improvement over RF ablation alone. Cylindrical implants were fabricated using 65% poly(D,L-lactide-co-glycolide) (PLGA), 21.5% NaCl, and 13.5% doxorubicin. Control or drug-containing millirods were implanted inside VX2 liver tumors (11 mm diameter) in rabbits after RF ablation. Therapeutic efficacy was assessed 4 and 8 days after treatment using tumor size, histology, and fluorescence measurement of drug distribution. Tumors in both test groups recurred at the boundary of the ablated region. Therapeutic doxorubicin concentrations were found in more than 80% of the ablated area, but concentrations declined rapidly at the boundary between normal and ablated tissue. This region was characterized by a developing fibrous capsule with resolving inflammation, which restricted drug transport out of the ablated zone. The intratumoral doxorubicin implants delivered high concentrations of drug within the ablated region but only limited amounts outside the ablation zone. Future studies will focus on overcoming the fibrotic transport barrier and enhancing drug delivery to the periphery of the ablation region to prevent tumor progression.

Three-dimensional spatial and temporal temperature imaging in gel phantoms using backscattered ultrasound

Thermal therapies such as radio frequency, heated saline, and high-intensity focused ultrasound ablations are often performed suboptimally due to the inability to monitor the spatial and temporal distribution of delivered heat and the extent of tissue necrosis. Ultrasound-based temperature imaging recently was proposed as a means to measure noninvasively the deposition of heat by tracking the echo arrival time shifts in the ultrasound backscatter caused by changes in speed of sound and tissue thermal expansion. However, the clinical applicability of these techniques has been hampered by the two-dimensional (2-D) nature of traditional ultrasound imaging, and the complexity of the temperature dependence of sound speed for biological tissues. In this paper, we present methodology, results, and validation of a 3-D spatial and temporal ultrasound temperature estimation technique in an alginate-based gel phantom to track the evolution of heat deposition over a treatment volume. The technique was experimentally validated for temperature rises up to approximately 10 degrees C by comparison with measurements from thermocouples that were embedded in the gel. Good agreement (rms difference = 0.12 degrees C, maximum difference = 0.24 degrees C) was observed between the noninvasive ultrasound temperature estimates and thermocouple measurements. Based on the results obtained for the temperature range studied in this paper, the technique demonstrates potential for applicability in image guidance of thermal therapy for determining the location of the therapeutic focal spot and assessing the extent of the heated region at subablative intensities.

Radiofrequency ablation for hepatocellular carcinoma and metastatic liver tumors: a comparative study

BACKGROUND

This study compared the effectiveness of radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC) and liver metastases.

METHODS

We compared the outcomes of 240 patients with HCC and 44 patients with liver metastases treated with RFA. Data were prospectively collected and retrospectively analyzed. Effects of different variables on recurrences were studied.

RESULTS

A total of 406 tumor nodules were treated. The median size of the largest ablated tumor was 2.5 cm, and the median tumor number was 1. Complete tumor ablation was achieved in 91.2%. Local recurrence rate was 15.4% after a median follow-up of 24.5 months. There was no significant impact of tumor pathology on local recurrence. However, patients with liver metastasis had higher extrahepatic recurrence rate (P = 0.019) and shorter disease-free survival (P = 0.007). Patients with multiple tumors had higher local (P = 0.047) and extrahepatic (P = 0.019) recurrence rates than those with a solitary tumor. Tumor size had an impact on local recurrence rate only in patients with liver metastasis with a higher rate in those with tumor > 2.5 cm in diameter (P = 0.028).

CONCLUSIONS

Tumor pathology does not appear to have a significant impact on local recurrence rates. RFA is effective in local tumor control for both HCC and liver metastasis.

Molecular pathogenesis of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common life-threatening malignancies in the world. This cancer generally arises within the boundaries of well-defined causal factors, of which viral hepatitis infection, aflatoxin exposure, chronic alcohol abuse, and nonalcoholic steatohepatitis are the major risk factors. Despite the identification of these etiological agents, hepatocarcinogenesis remains poorly understood. The molecular mechanisms leading to the development of HCC appear extremely complex and only recently have begun to be elucidated. Currently, surgical resection or liver transplantation offer the best chance of cure for the patient with HCC; however, these therapies are hindered by inability of many of these patients to undergo liver resection, by tumor recurrence and by donor shortages. A lack of suitable therapeutic strategies has led to a greater focus on prevention of HCC using antiviral agents and vaccination. Overall, the current outlook for patients with HCC is bleak; however, a better understanding of the molecular and genetic basis of this cancer should lead to the development of more efficacious therapies.

Synergy between in situ cryoablation and TLR9 stimulation results in a highly effective in vivo dendritic cell vaccine

Dendritic cells (DC) are professional antigen-presenting cells that play a pivotal role in the induction of immunity. Ex vivo-generated, tumor antigen-loaded mature DC are currently exploited as cancer vaccines in clinical studies. However, antigen loading and maturation of DC directly in vivo would greatly facilitate the application of DC-based vaccines. We have previously shown that in situ tumor destruction by ablative treatments efficiently delivers antigens for the in vivo induction of antitumor immunity. In this article, we show that although 20% of the draining lymph node DCs acquire intratumorally injected model antigens after in situ cryoablation, only partial protection against a subsequent tumor rechallenge is observed. However, we also show that a combination treatment of cryoablation plus TLR9 stimulation via CpG-oligodeoxynucleotides is far more effective in the eradication of local and systemic tumors than either treatment modality alone. Analysis of the underlying mechanism revealed that in situ tumor ablation synergizes with TLR9 stimulation to induce DC maturation and efficient cross-presentation in tumor-bearing mice, leading to superior DC function in vivo. Therefore, in situ tumor destruction in combination with CpG-oligodeoxynucleotide administration creates a unique "in situ DC vaccine" that is readily applicable in the clinic.

Selective portal clamping to minimize hepatic ischaemia-reperfusion damage and avoid accelerated outgrowth of experimental colorectal liver metastases

BACKGROUND

Temporary vascular clamping during local ablation for colorectal liver metastases increases destruction volumes. However, it also causes ischaemia-reperfusion (IR) injury to the liver parenchyma and accelerates the outgrowth of microscopic tumour deposits. The aim of this study was to investigate the effects of selective portal clamping on hepatocellular damage and tumour growth.

METHODS

Mice carrying pre-established hepatic colorectal micrometastases underwent either simultaneous clamping of both the portal vein and the hepatic artery or selective clamping of the portal vein to the median and left liver lobes for 45 min. Sham-operated mice served as controls. Hepatic injury and tumour growth were assessed over time.

RESULTS

Standard inflow occlusion resulted in a rise in liver enzymes, a local inflammatory response and hepatocellular necrosis. The outgrowth of pre-established micrometastases was accelerated three- to fourfold in clamped compared with non-clamped liver lobes (27.4 versus 7.8 per cent, P < 0.010). Conversely, selective portal clamping induced minimal liver injury, tissue inflammation or hepatocellular necrosis, and completely stopped the accelerated outgrowth of micrometastases.

CONCLUSION

Selective portal clamping does not induce liver tissue damage or accelerate micrometastasis outgrowth and may therefore be the preferable clamping method during local ablative treatment of hepatic metastases.

Efficient loading of dendritic cells following cryo and radiofrequency ablation in combination with immune modulation induces anti-tumour immunity

Dendritic cells (DC) are professional antigen-presenting cells that play a pivotal role in the induction of immunity. Ex vivo-generated, tumour antigen-loaded mature DC are currently exploited as cancer vaccines in clinical studies. However, antigen loading and maturation of DC directly in vivo would greatly facilitate the application of DC-based vaccines. We formerly showed in murine models that radiofrequency-mediated tumour destruction can provide an antigen source for the in vivo induction of anti-tumour immunity, and we explored the role of DC herein. In this paper we evaluate radiofrequency and cryo ablation for their ability to provide an antigen source for DC and compare this with an ex vivo-loaded DC vaccine. The data obtained with model antigens demonstrate that upon tumour destruction by radiofrequency ablation, up to 7% of the total draining lymph node (LN) DC contained antigen, whereas only few DC from the conventional vaccine reached the LN. Interestingly, following cryo ablation the amount of antigen-loaded DC is almost doubled. Analysis of surface markers revealed that both destruction methods were able to induce DC maturation. Finally, we show that in situ tumour ablation can be efficiently combined with immune modulation by anti-CTLA-4 antibodies or regulatory T-cell depletion. These combination treatments protected mice from the outgrowth of tumour challenges, and led to in vivo enhancement of tumour-specific T-cell numbers, which produced more IFN-γ upon activation. Therefore, in situ tumour destruction in combination with immune modulation creates a unique, ‘in situ DC-vaccine’ that is readily applicable in the clinic without prior knowledge of tumour antigens.

Optimization of wet radiofrequency ablation using a perfused-cooled electrode: a comparative study in ex vivo bovine livers

Objective

To determine the optimized protocol for wet monopolar radiofrequency ablation (RFA) using a perfused-cooled electrode to induce coagulation necrosis in the ex vivo bovine liver.

Materials and Methods

Radiofrequency was applied to excised bovine livers in a monopolar mode using a 200W generator with an internally cooled electrode (groups A and B) or a perfused-cooled electrode (groups C, D, E, and F) at maximum power (150-200 W) for 10 minutes. A total of 60 ablation zones were created with six different regimens: group A - dry RFA using intra-electrode cooling; group B - dry RFA using intra-electrode cooling and a pulsing algorithm; group C - wet RFA using only interstitial hypertonic saline (HS) infusion; group D - wet RFA using interstitial HS infusion and a pulsing algorithm; group E - wet RFA using interstitial HS infusion and intra-electrode cooling; and group F - wet RFA using interstitial HS infusion, intra-electrode cooling and a pulsing algorithm. In groups C, D, E, and F, RFA was performed with the infusion of 6% HS through the perfused cooled electrode at a rate of 2 mL/minute. During RFA, we measured the tissue temperature at a distance of 15 mm from the electrode. The dimensions of the ablation zones and the changes in impedance, currents, and liver temperature during RFA were compared between these six groups.

Results

During RFA, the mean tissue impedances in groups A (243 ± 88 Ω) and C (252.5 ± 108 Ω) were significantly higher than those in groups B (85 ± 18.7 Ω), D (108.2 ± 85 Ω), E (70.0 ± 16.3 Ω), and F (66.5 ± 7 Ω) (p < 0.05). The mean currents in groups E and F were significantly higher than those in groups B and D, which were significantly higher than those in groups A and C (p < 0.05): 520 ± 425 mA in group A, 1163 ± 34 mA in group B, 652.5 ± 418 mA in group C, 842.5 ± 773 mA in group D, 1665 ± 295 mA in group E, and 1830 ± 109 mA in group F. The mean volumes of the ablation regions in groups E and F were significantly larger than those in the other groups (p < 0.05): 17.7 ± 5.6 cm³ in group A, 34.5 ± 3.0 cm³ in group B, 20.2 ± 15.6 cm³ in group C, 36.1 ± 19.5 cm³ in group D, 68.1 ± 12.4 cm³ in group E, and 79.5 ± 31 cm³ in group F. The final tissue temperatures at a distance of 15 mm from the electrode were higher in groups E and F than those in groups A, C, and D (p < 0.05): 50 ± 7.5℃ in group A, 66 ± 13.6℃ in group B, 60 ± 13.4℃ in group C, 61 ±12.7℃ in group D, 78 ± 14.2℃ in group E, and 79 ± 12.0℃ in group F.

Conclusion

Wet monopolar RFA, using intra-electrode cooling and interstitial saline infusion, showed better performance in creating a large ablation zone than either dry RFA or wet RFA without intra-electrode cooling.

In vivo results of a new focal tissue ablation technique: irreversible electroporation

This paper reports results of in vivo experiments that confirm the feasibility of a new minimally invasive method for tissue ablation, irreversible electroporation (IRE). Electroporation is the generation of a destabilizing electric potential across biological membranes that causes the formation of nanoscale defects in the lipid bilayer. In IRE, these defects are permanent and lead to cell death. This paper builds on our earlier theoretical work and demonstrates that IRE can become an effective method for nonthermal tissue ablation requiring no drugs. To test the capability of IRE pulses to ablate tissue in a controlled fashion, we subjected the livers of male Sprague-Dawley rats to a single 20-ms-long square pulse of 1000 V/cm, which calculations had predicted would cause nonthermal IRE. Three hours after the pulse, treated areas in perfusion-fixed livers exhibited microvascular occlusion, endothelial cell necrosis, and diapedeses, resulting in ischemic damage to parenchyma and massive pooling of erythrocytes in sinusoids. However, large blood vessel architecture was preserved. Hepatocytes displayed blurred cell borders, pale eosinophilic cytoplasm, variable pyknosis and vacuolar degeneration. Mathematical analysis indicates that this damage was primarily nonthermal in nature and that sharp borders between affected and unaffected regions corresponded to electric fields of 300-500 V/cm.