Radiofrequency ablation of porcine liver in vivo: effects of blood flow and treatment time on lesion size

Does Radiofrequency Ablation Add to Chemotherapy for Unresectable Liver Metastases?

In patients with unresectable colorectal liver metastases (CRLM), radiofrequency ablation (RFA) might be a good alternative, whenever possible. In contrast to systemic therapy, the aim of RFA is to achieve complete local tumor control in an attempt to provide long-term survival. In this article we discuss the available evidence regarding the treatment of patients with unresectable CRLM, focusing on RFA in conjunction with modern systemic therapies. We observed that the available evidence in the existing literature is limited, and often consists of level 2 and 3 evidence, thereby hampering any firm conclusions. Nonetheless, RFA seems superior to chemotherapy alone in patients with liver-only disease amenable for RFA. However, the combination of RFA and chemotherapy has been demonstrated to be feasible and safe, lending support to the concept of RFA followed by chemotherapy, in order to reduce local recurrence rates and prolong survival.

A comparison of direct heating during radiofrequency and microwave ablation in ex vivo liver

PURPOSE

This study was designed to determine the magnitude and spatial distribution of temperature elevations when using 480 kHz RF and 2.45 GHz microwave energy in ex vivo liver models.

METHODS

A total of 60 heating cycles (20 s at 90 W) were performed in normal, RF-ablated, and microwave-ablated liver tissues (n = 10 RF and n = 10 microwave in each tissue type). Heating cycles were performed using a 480-kHz generator and 3-cm cooled-tip electrode (RF) or a 2.45-GHz generator and 14-gauge monopole (microwave) and were designed to isolate direct heating from each energy type. Tissue temperatures were measured by using fiberoptic thermosensors 5, 10, and 15 mm radially from the ablation applicator at the depth of maximal heating. Power delivered, sensor location, heating rates, and maximal temperatures were compared using mixed effects regression models.

RESULTS

No significant differences were noted in mean power delivered or thermosensor locations between RF and microwave heating groups (P > 0.05). Microwaves produced significantly more rapid heating than RF at 5, 10, and 15 mm in normal tissue (3.0 vs. 0.73, 0.85 vs. 0.21, and 0.17 vs. 0.09 °C/s; P < 0.05); and at 5 and 10 mm in ablated tissues (2.3 ± 1.4 vs. 0.7 ± 0.3, 0.5 ± 0.3 vs. 0.2 ± 0 °C/s, P < 0.05). The radial depth of heating was ~5 mm greater for microwaves than RF.

CONCLUSIONS

Direct heating obtained with 2.45-GHz microwave energy using a single needle-like applicator is faster and covers a larger volume of tissue than 480-kHz RF energy.

Sequential combination treatment (arterial embolization and percutaneous radiofrequency ablation) of inoperable renal cell carcinoma: single-center pilot study

BACKGROUND

Potential drawbacks of percutaneous radiofrequency ablation (RFA) for renal cell carcinoma (RCC) include local recurrence after RFA due to a limited ablation area, massive hemorrhage induced by kidney puncture, and difficulty in visualizing the tumor at CT-guided puncture.

PURPOSE

To evaluate retrospectively the technical success, effectiveness, and complications elicited in patients with unresectable RCC following single-session sequential combination treatment consisting of renal arterial embolization followed by RFA.

MATERIAL AND METHODS

Ten patients (12 RCCs) who were not candidates for surgery were included in this pilot study. All tumors ranged from 18-66 mm in size (mean 31 ± 3.9 mm), and were percutaneously ablated several hours after embolization of the tumor vessels with iodized oil and gelatin sponges. We evaluated the technical success, effectiveness, effect on renal function, and complications of this treatment. Effectiveness was judged on CT and/or MR images obtained every three months after RFA. The effect on renal function was assessed based on the creatinine level and glomerular filtration rate (GFR) before, one week, and three months after the procedure.

RESULTS

Renal arterial embolization followed by percutaneous RFA was technically successful in all patients. On contrast CT and/or MR images obtained one week and three months after RFA we observed necrosis in the embolized segment of all RCCs. There were no major complications during and after the procedure. All patients reported tolerable pain and a burning sensation during RFA. After the procedure, five patients (50%) experienced back pain, one each manifested fluid collection, subcapsular hematomas, hematuria, or nausea. There were no instances of recurrence during a mean follow-up period of 47 ± 3.8 months. We noted no significant difference in serum creatinine and GFR before and after treatment.

CONCLUSION

Our pilot study suggests that sequential combination treatment by renal arterial embolization followed by percutaneous RFA is feasible in patients with inoperable RCC. The treatment complications were acceptable and excellent effects were obtained.

Cryoablation vs radiofrequency ablation for the treatment of renal cell carcinoma: a meta-analysis of case series studies

Study Type - Therapy (systematic review). Level of Evidence 2b What's known on the subject? and What does the study add? The oncological success of partial nephrectomy in the treatment of small renal masses is well established. However, partial nephrectomy has largely supplanted the radical approach. In the last decade, laparoscopy has been adopted as the new surgical approach for the treatment of renal cell carcinoma. Laparoscopy offers the advantage of lower analgesic use, shorter hospital stay, and quicker recovery time. More recently, ablative technologies have been investigated as an alternative to laparoscopic partial nephrectomy. These techniques can often be performed percutaneously in the radiology suite, or laparoscopically without the need for hilar clamping. However, only the cryoablation and radiofrequency ablation modalities have had widespread use with several series reporting short to intermediate results. This review shows that both cryoablation and radiofrequency ablation are promising therapies in patients with small renal tumours (<4 cm), who are considered poor candidates for more involved surgery.

OBJECTIVE

• To determine the current status of the literature regarding the clinical efficacy and complication rates of cryoablation vs radiofrequency ablation in the treatment of small renal tumours.

METHODS

• A review of the literature was conducted. There was no language restriction. Studies were obtained from the following sources: MEDLINE, EMBASE and LILACS. • Inclusion criteria were (i) case series design with more than one case reported, (ii) use of cryoablation or radiofrequency ablation, (iii) patients with renal cell carcinoma and, (iv) outcome reported as clinical efficacy. • When available, we also quantified the complication rates from each included study. • Proportional meta-analysis was performed on both outcomes with a random-effects model. The 95% confidential intervals were also calculated.

RESULTS

• Thirty-one case series (20 cryoablation, 11 radiofrequency ablation) met all inclusion criteria. • The pooled proportion of clinical efficacy was 89% in cryoablation therapy from a total of 457 cases. There was a statistically significant heterogeneity between these studies showing the inconsistency of clinical and methodological aspects. • The pooled proportion of clinical efficacy was 90% in radiofrequency ablation therapy from a total of 426 cases. There was no statistically significant heterogeneity between these studies. • There was no statistically significant difference regarding complications rate between cryoablation and radiofrequency ablation.

CONCLUSIONS

• This review shows that both ablation therapies have similar efficacy and complication rates. • There is urgency for performing clinical trials with long-term data to establish which intervention is most suitable for the treatment of small renal masses.

Venous thrombosis after radiofrequency ablation for hepatocellular carcinoma

OBJECTIVE

This study was designed to evaluate the frequency, morphological patterns, sequential changes, and clinical significance of venous thrombosis after radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

A total of 1379 RFAs performed in 1046 patients with HCC (mean tumor size, 1.93 cm) were surveyed. We retrospectively reviewed all radiologic reports before and after RFA and selected 15 patients with newly developed procedure-related venous thrombosis. Procedure-related thrombosis was defined as being adjacent to the ablation zone and developing within 4 months after the procedure. We evaluated the frequency, morphological patterns, sequential changes, and clinical course of venous thrombosis (mean follow-up, 662.9 days). Four cases with local tumor progression were identified among the 15 patients, and their clinical implications were evaluated.

RESULTS

A total of 15 venous thromboses (1.08%; 12 portal and three hepatic veins) developed after RFA (range, 0-128 days; mean, 37 days). The thromboses were found in central (n = 10), peripheral (n = 4), and both central and peripheral (n = 1) locations in the ablation zones. Thrombosis was decreased in nine (69.2%), persisted in one (7.6%), and increased in three (23.0%) of 13 patients who underwent follow-up CT for more than 12 months. Local tumor progression was noted in four patients (26.6%); it abutted to venous thrombosis in two patients, separated from the venous thrombosis in one patient, and exhibited malignant thrombosis in one patient.

CONCLUSION

The development of portal or hepatic venous thromboses after RFA in patients with HCC is rare and usually is associated with favorable prognoses. Further investigation is warranted to elucidate whether venous thrombosis after RFA is related to local tumor progression around ablation zones.

Combination radiofrequency (RF) ablation and IV liposomal heat shock protein suppression: reduced tumor growth and increased animal endpoint survival in a small animal tumor model

BACKGROUND

To investigate the effect of IV liposomal quercetin (a known down-regulator of heat shock proteins) alone and with liposomal doxorubicin on tumor growth and end-point survival when combined with radiofrequency (RF) tumor ablation in a rat tumor model.

METHODS

Solitary subcutaneous R3230 mammary adenocarcinoma tumors (1.3-1.5 cm) were implanted in 48 female Fischer rats. Initially, 32 tumors (n=8, each group) were randomized into four experimental groups: (a) conventional monopolar RF alone (70°C for 5 min), (b) IV liposomal quercetin alone (1 mg/kg), (c) IV liposomal quercetin followed 24hr later with RF, and (d) no treatment. Next, 16 additional tumors were randomized into two groups (n=8, each) that received a combined RF and liposomal doxorubicin (15 min post-RF, 8 mg/kg) either with or without liposomal quercetin. Kaplan-Meier survival analysis was performed using a tumor diameter of 3.0 cm as the defined survival endpoint.

RESULTS

Differences in endpoint survival and tumor doubling time among the groups were highly significant (P<0.001). Endpoint survivals were 12.5±2.2 days for the control group, 16.6±2.9 days for tumors treated with RF alone, 15.5±2.1 days for tumors treated with liposomal quercetin alone, and 22.0±3.9 days with combined RF and quercetin. Additionally, combination quercetin/RF/doxorubicin therapy resulted in the longest survival (48.3±20.4 days), followed by RF/doxorubicin (29.9±3.8 days).

CONCLUSIONS

IV liposomal quercetin in combination with RF ablation reduces tumor growth rates and improves animal endpoint survival. Further increases in endpoint survival can be seen by adding an additional anti-tumor adjuvant agent liposomal doxorubicin. This suggests that targeting several post-ablation processes with multi-drug nanotherapies can increase overall ablation efficacy.

Dual-row needle arrays under an electromagnetic thermotherapy system for bloodless liver resection surgery

Electromagnetic thermotherapy has been extensively investigated recently and may become a new surgical modality for a variety of medical applications. It applies a high-frequency alternating magnetic field to heat up magnetic materials inserted within the human body to generate tissue coagulation or cell apoptosis. Using a new procedure with dual-row needle arrays under an electromagnetic thermotherapy system with a feedback temperature control system, this study demonstrates bloodless porcine liver resection, which is challenging using existing methods. In vitro experiments showed that hollowed, stainless-steel needles could be heated up to more than 300 °C within 30 s when centered under the induction coils of the electromagnetic thermotherapy system. In order to generate a wide ablation zone and to prevent the dual-row needle arrays from sticking to the tissue after heating, a constant temperature of 120 °C was applied using a specific treatment protocol. The temperature distribution in the porcine livers was also measured to explore the effective coagulation area. Liver resection was then performed in Lan-Yu pigs. Experimental results showed that seven pigs underwent liver resection without bleeding during surgery and no complications afterward. The dual-row needle arrays combined with the electromagnetic thermotherapy system are thus shown to be promising for bloodless tissue resection.

Radiofrequency ablation combined with liposomal quercetin to increase tumour destruction by modulation of heat shock protein production in a small animal model

PURPOSE

To investigate the effect of heat shock protein (HSP) modulation on tumour coagulation by combining radiofrequency (RF) ablation with adjuvant liposomal quercetin and/or doxorubicin in a rat tumour model.

METHODS

Sixty R3230 breast adenocarcinoma tumours/animals were used in this IACUC-approved study. Initially, 60 tumours (n=6, each subgroup) were randomised into five groups: (1) RF alone, (2) intravenous (IV) liposomal quercetin alone (1 mg/kg), (3) IV liposomal quercetin followed 24 h later with RF, (4) RF followed 15 min later by IV liposomal doxorubicin (8 mg/kg), (5) IV liposomal quercetin 24 h before RF followed by IV liposomal doxorubicin 15 min post-ablation. Animals were sacrificed 4 or 24 h post-treatment and gross coagulation diameters were compared. Next, immunohistochemistry staining was performed for Hsp70 and cleaved caspase-3 expression. Comparisons were performed by using Student t-tests or ANOVA.

RESULTS

Combination RF-quercetin significantly increased coagulation size compared with either RF or liposomal quercetin alone (13.1±0.7 mm vs. 8.8±1.2 mm or 2.3±1.3 mm, respectively, P<0.001 for all comparisons). Triple therapy (quercetin-RF-doxorubicin) showed larger coagulation diameter (14.5±1.0 mm) at 24 h than quercetin-RF (P=0.016) or RF-doxorubicin (13.2±1.3 mm, P=0.042). Combination quercetin-RF decreased Hsp70 expression compared with RF alone at both 4 h (percentage of stained cells/hpf 22.4±13.9% vs. 38.8±16.1%, P<0.03) and 24 h (45.2±10.5% vs. 81.1±3.6%, P<0.001). Quercetin-RF increased cleaved caspase-3 expression at both 4 h (percentage of stained cells/hpf 50.7±13.4% vs. 41.9±15.1%, P<0.03) and 24 h (37.4±7.8% vs. 33.2±6.5%, P=0.045); with, triple therapy (quercetin-RF-doxorubicin) resulting in the highest levels of apoptosis (45.1±10.7%) at 24 h. Similar trends were observed for rim thickness.

CONCLUSIONS

Suppression of HSP production using adjuvant liposomal quercetin can increase apoptosis and improve RF ablation-induced tumour destruction. Further increases in tumour coagulation can be seen including an additional anti-tumour adjuvant agent such as liposomal doxorubicin.

Effect of interval between transcatheter hepatic arterial embolization and radiofrequency ablation on ablated lesion size in a swine model

PURPOSE

The aim of the study was to clarify the effect of the interval between transcatheter hepatic arterial embolization (TAE) with Lipiodol plus gelatin sponge particles and radiofrequency (RF) ablation on the extent of ablation.

MATERIALS AND METHODS

Eight healthy swine were divided into four groups: RF ablation (ablation only), RF ablation immediately after TAE (immediate ablation), RF ablation 3 days after TAE (3-day ablation), and RF ablation 6 days after TAE (6-day ablation). Five ablated lesions were created in each swine (10 per group). A 2-cm expandable LeVeen needle electrode was used for RF ablation. Ablated lesions are composed of an outer reddish zone and an inner whitish zone.

RESULTS

The average longest length of the major, intermediate, and minor axes and the volume in the immediate ablation, 3-day ablation, and 6-day ablation groups were significant longer and greater (1.52 and 1.52, 1.46 and 1.50, and 1.37 and 1.35 times greater in the red zone and the whitish area, respectively) than those in the ablation-only group (P < 0.05/3). Accumulation of Lipiodol was still noted in the hepatic sinusoids in the 3-day and 6-day ablation groups.

CONCLUSION

RF ablation delayed to 6 days following TAE produced larger ablation volumes than did RF ablation alone.

Comparison between different thickness umbrella-shaped expandable radiofrequency electrodes (SuperSlim and CoAccess): Experimental and clinical study

The purpose of the present study was to compare the size and configuration of the ablation zones created by SuperSlim and CoAccess electrodes, using various ablation algorithms in ex vivo bovine liver and in clinical cases. In the experimental study, we ablated explanted bovine liver using 2 types of electrodes and 4 ablation algorithms (combinations of incremental power supply, stepwise expansion and additional low-power ablation) and evaluated the ablation area and time. In the clinical study, we compared the ablation volume and the shape of the ablation zone between both electrodes in 23 hepatocellular carcinoma (HCC) cases with the best algorithm (incremental power supply, stepwise expansion and additional low-power ablation) as derived from the experimental study. In the experimental study, the ablation area and time by the CoAccess electrode were significantly greater compared to those by the SuperSlim electrode for the single-step (algorithm 1, p=0.0209 and 0.0325, respectively) and stepwise expansion algorithms (algorithm 2, p=0.0002 and <0.0001, respectively; algorithm 3, p= 0.006 and 0.0407, respectively). However, differences were not significant for the additional low-power ablation algorithm. In the clinical study, the ablation volume and time in the CoAccess group were significantly larger and longer, respectively, compared to those in the SuperSlim group (p=0.0242 and 0.009, respectively). Round ablation zones were acquired in 91.7% of the CoAccess group, while irregular ablation zones were obtained in 45.5% of the SuperSlim group (p=0.0428). In conclusion, the CoAccess electrode achieves larger and more uniform ablation zones compared with the SuperSlim electrode, though it requires longer ablation times in experimental and clinical studies.

Laparoscopic treatment of liver tumours using a two-needle probe bipolar radiofrequency ablation device

BACKGROUND

Many hepatobiliary centres are increasingly utilizing thermocoagulative devices such as bipolar-radiofrequency ablation (B-RFA). Compared with monopolar-radiofrequency ablation (M-RFA), B-RFA does not require grounding pads, thereby avoiding dermal burn injuries, and does not position probes directly into the tumour but rather on the perimeter. Additionally, B-RFA can precoagulate parenchyma to assist in hepatic resection. Herein, we report our early experience using B-RFA.

METHODS

A retrospective review identified 68 patients who underwent M-RFA or B-RFA between June 2004 and September 2010 in an academic centre. Peri-operative metrics were analysed.

RESULTS

M-RFA was used to treat 30 patients, whereas B-RFA was used for 17 patients. There were no differences in peri-operative metrics, survival or disease recurrence between M-RFA and B-RFA. Seventeen additional patients underwent B-RFA precoagulation during laparoscopic resection (segmentectomy in eleven patients and multi-segmental resection in six patients). Four patients with multifocal disease underwent procedures that combined B-RFA with resection.

CONCLUSIONS

The early experience utilizing B-RFA demonstrates equivalency to M-RFA with respect to peri-operative metrics and survival. Moreover, B-RFA can be utilized to precoagulate tissue during a planned resection, making it not only a useful tool for tumour therapy but also a useful adjunct during surgical resections.

International multicentre prospective study on microwave ablation of liver tumours: preliminary results

BACKGROUND

Microwave ablation (MWA) is increasingly utilized in the treatment of hepatic tumours. Promising single-centre reports have demonstrated its safety and efficacy, but this modality has not been studied in a prospective, multicentre study.

METHODS

Eighteen international centres recorded operative and perioperative data for patients undergoing MWA for tumours of any origin in a voluntary Internet-based database. All patients underwent operative MWA using a 2.45-GHz generator with a 5-mm antenna.

RESULTS

Of the 140 patients, 114 (81.4%) were treated with MWA alone and 26 (18.6%) were treated with MWA combined with resection. Multiple tumours were treated with MWA in 40.0% of patients. A total of 299 tumours were treated in these 140 patients. The median size of ablated lesions was 2.5 cm (range: 0.5-9.5 cm). Tumours were treated with a median of one application (range: 1-6 applications) for a median of 4 min (range: 0.5-30.0 min). A power setting of 100 W was used in 78.9% of cases. Major morbidity was 8.3% and in-hospital mortality was 1.9%.

CONCLUSIONS

These multi-institution data demonstrate rapid ablation time and low morbidity and mortality rates in patients undergoing operative MWA with a high rate of multiple ablations and concomitant hepatic resection. Longterm follow-up will be required to determine the efficacy of MWA relative to other forms of ablative therapy.

[US-guided percutaneous radio frequency in kidney cancer: our experience]

The radio frequency ablation of kidney cancer showed satisfactory results at a short follow-up with the use of a new RF generator system. Radio frequency is an alternative procedure with the intention of producing heat damage to tissue by electromagnetic energy.

METHODS

From January 2009 to July 2010, at our operative unit, ten patients (age range: 50-83 years) underwent percutaneous radio frequency. All tumors were primitive without secondarism. The lesion diameter ranged from 15 to 35 mm. Only in two cases the treatment was open due to difficulties in finding the lesion.

RESULTS

At six months' treatment, two patients had a complete remission and one patient an incomplete one; at eight months, five patients are with a complete remission and one patient with complete remission; at twelve months, one patient showed an incomplete remission.

CONCLUSIONS

There are no studies with a long-term follow-up and it is prudent to limit this therapy to those patients who can not undergo surgical treatment. A correct post-operative imaging evaluation is essential to ensure an effective treatment.

Review of the efficacy and safety of radiofrequency ablation for the treatment of small renal masses

BACKGROUND

Small renal masses are increasingly being discovered incidentally on imaging performed for another reason. The standard of care for 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 for these masses. We sought to evaluate the efficacy and safety of radiofrequency ablation in the treatment of renal tumours.

METHODS

We conducted a review of the literature. There was no language restriction. We obtained studies from the following sources: the Cochrane Library, PubMed, EMBASE, LILACS and Current Controlled Trials.

RESULTS

We identified no clinical trials in the literature. Thus we described the results from case series and retrospective studies with a reasonable sample size (number of reported patients in each study > 65). Most patients undergoing RFA had T1a disease with a mean tumour size of about 3 cm. Radiofrequency ablation was usually performed percutaneously with image guidance. Reported follow-up was short and ranged from 1 to 30 months. Most series used radiographic response as a surrogate for cancer control. The rates of local recurrence of the tumour were as high as 13.0% (average 8.5%) and were slightly higher than those associated with cryoablation and partial nephrectomy. Complications included hemorrhage, ureteral strictures and loss of a renal unit.

CONCLUSION

Our review demonstrates that RFA is a suitable and promising therapy in patients with small renal tumours who are considered to be poor candidates for more involved surgery. However, clinical trials with long-term data are needed to establish the oncological efficacy.

Radiofrequency ablation as a treatment strategy for liver metastases from breast cancer

The American Cancer Society estimates that in 2007, 178,000 women in the United States will be diagnosed, and that 40,000 women will die from breast cancer. Metastatic breast cancer is a systemic disease, uncommonly involving an isolated organ. Liver metastases from breast cancer occur in ~50% of the patients who develop breast cancer metastases and are associated with a poor outcome. Hepatic metastasectomy as an adjuvant treatment even in patients with stable extrahepatic disease has been shown to impart a significant survival advantage over chemotherapy alone. In the treatment of hepatocellular carcinoma (HCC) and colorectal liver metastases (CRLM), radiofrequency ablation (RFA) has been shown to be a safe, minimally invasive treatment option with low morbidity and short hospital stay that is more readily repeatable than resection. The data supporting RFA of breast cancer liver metastases (BCLM) is currently limited to small, retrospective series that, like hepatic resection, have demonstrated adjuvant RFA improves survival compared with chemotherapy alone. This review will examine the rationale, indications, supportive data, and complications of RFA in the treatment of BCLM.

Assisted hepatic resection using a toroidal HIFU device: an in vivo comparative study in pig

PURPOSE

Bleeding is the main cause of postoperative complications during hepatic surgery. Blood loss and transfusions increase tumor recurrence in liver metastases from colorectal cancer. A high intensity focused ultrasound (HIFU) device with an integrated ultrasound imaging probe was developed for the treatment of colorectal liver metastasis.

METHODS

The HIFU toroidal-shaped transducer contains 256 elements (working frequency: 3 MHz) and can create a single conical lesion of 7 cm3 in 40 s. Then, the volume of treatment can be significantly increased by juxtaposing single lesions. Presented here is the use of this device in an animal model as a complementary tool to improve surgical resection in the liver. Before transecting the liver, a wall of coagulative necrosis was performed using this device in order to minimize blood loss and dissection time during hepatectomy. Resection assisted by HIFU was compared to classical dissections with clamping [intermittent Pringle maneuver (IPM) group] and without clamping (control group). For each technique, 14 partial liver resections were performed in seven pigs. Blood loss per dissection surface area and resection time were the main outcome parameters.

RESULTS

Conserving liver blood inflow during hepatic resection assisted by HIFU did not increase total blood loss (7.4 +/- 3.3 ml cm(-2)) compared to hepatic resection performed during IPM and controlled blood inflow (11.2 +/- 2.2 ml cm(-2)). Lower blood loss was measured on average when using HIFU, even though difference with clamping (IPM) was not statistically significant (p = 0.09). Resection assisted by HIFU reduced blood loss by 50% compared to control group (14.0 +/- 3.4 ml cm(-2), p = 0.03). The duration of transection when using HIFU (13 +/- 3 min) was significantly lower compared to clamping (23 +/- 4 min, p < 0.01) and control (18 +/- 3 min, p = 0.02). Precoagulation also resulted in sealing blood vessels with a diameter of less than 5 mm, and therefore the number of clips needed in the HIFU group was significantly lower (0.8 +/- 0.2 cm(-2)) when compared to clamping (1.6 +/- 0.2 cm(-2), p < 0.01) and control (1.8 +/- 0.4 cm(-2), p < 0.01).

CONCLUSIONS

This method holds promise for future clinical applications in resection of liver metastases.

In vivo validation of a therapy planning system for laser-induced thermotherapy (LITT) of liver malignancies

PURPOSE

In situ ablation is increasingly being used for the treatment of liver malignancies. The application of these techniques is limited by the lack of a precise prediction of the destruction volume. This holds especially true in anatomically difficult situations, such as metastases in the vicinity of larger liver vessels. We developed a three-dimensional (3D) planning system for laser-induced thermotherapy (LITT) of liver tumors. The aim of the study was to validate the system for calculation of the destruction volume.

METHODS

LITT (28 W, 20 min) was performed in close contact to major hepatic vessels in six pigs. After explantation of the liver, the coagulation area was documented. The liver and its vascular structures were segmented from a pre-interventional CT scan. Therapy planning was carried out including the cooling effect of adjacent liver vessels. The lesions in vivo and the simulated lesions were compared with a morphometric analysis.

RESULTS

The volume of lesions in vivo was 6,568.3 ± 3,245.9 mm(3), which was not different to the simulation result of 6,935.2 ± 2,538.5 mm(3) (P = 0.937). The morphometric analysis showed a sensitivity of the system of 0.896 ± 0.093 (correct prediction of destructed tissue). The specificity was 0.858 ± 0.090 (correct prediction of vital tissue).

CONCLUSIONS

A 3D computer planning system for the prediction of thermal lesions in LITT was developed. The calculation of the directional cooling effect of intrahepatic vessels is possible for the first time. The morphometric analysis showed a good correlation under clinical conditions. The pre-therapeutic calculation of the ablation zone might be a valuable tool for procedure planning.

Interstitial laser thermotherapy of a rat liver tumour: effect of hepatic inflow occlusion

BACKGROUND AND OBJECTIVE

Interstitial laser thermotherapy was used to treat rat liver tumours. The aim was to investigate the influence of temperature and temporary hepatic inflow occlusion on tumour growth and blood perfusion.

STUDY DESIGN/MATERIALS AND METHODS

Liver tumours were treated at 44°C at the tumour border for 30 minutes, hepatic inflow occlusion only, or a combination of these methods. Interstitial laser Doppler flowmetry was used to measure hepatic perfusion at the tumour border during and after heat treatment, for a total time of 60 minutes. Tumour growth was evaluated 6 days after treatment.

RESULTS

Tumours subjected to the combined treatment of hepatic inflow occlusion and interstitial laser thermotherapy displayed a blood perfusion reduction 30 minutes after treatment to 18 ± 5% of initial perfusion, which was significantly lower than achieved with thermotherapy alone (52 ± 10%, P = 0.02). The combined treatment and treatment with thermotherapy alone resulted in relative tumour growth of 0.3 ± 0.1 and 1.0 ± 0.2, respectively (P = 0.04).

CONCLUSION

Inflow occlusion enhanced the effect of thermotherapy not by augmenting treatment temperatures but by increasing the thermal sensitivity of the tumour, reflected by an immediate effect on tumour blood perfusion.

Partial response of hepatocellular carcinoma to percutaneous microwave ablation: risk factors and preventive measures

AIM: To investigate the risk factors and preventive measures for partial response of hepatocellular carcinoma to percutaneous microwave ablation.

METHODS: The clinical data for 465 patients with hepatocellular carcinoma (796 tumor nodules) who underwent percutaneous microwave ablation from October 2004 to June 2010 were retrospectively analyzed. The risk factors and preventive measures for partial response to percutaneous microwave ablation were summarized.

RESULTS: Partial response occurred in 48 patients (69 tumor nodules), and the overall partial response rate was 9.15% (69/754). Of these 48 patients, 45 (64 tumor nodules) underwent percutaneous microwave ablation again and achieved complete ablation in 93.94% (62/64) of tumor nodules; 1 (2 tumor nodules) received percutaneous ethanol injection and achieved successful ablation; and 2 received palliative surgery. The incidence of partial response was positively correlated with large tumor diameter, tumor location (at the hepatic hilum or near the diaphragm or hepatic capsule), multiple tumors, and ill-defined margins on ultrasound(all P < 0.01), and complete ablation was negatively correlated with previous treatment by TACE (3.60% vs 12.39%, P < 0.01). Multivariate analysis showed that tumor size, number of nodules, tumor location, and previous treatment by TACE were independent risk factors for partial response of hepatocellular carcinoma to percutaneous microwave ablation.

CONCLUSION: Large tumor size, multiple tumors, subcapsular lesion, and previous treatment by TACE are often associated with partial response of hepatocellular carcinoma to percutaneous microwave ablation. Percutaneous microwave ablation is an effective and safe method for treatment of partial response of hepatocellular carcinoma.

Irreversible electroporation of the pancreas: definitive local therapy without systemic effects

BACKGROUND

The use of thermal tumor ablative techniques in the pancreas is limited due to the risk of pancreatitis and damage to major vascular structures. Irreversible electroporation (IRE) is a non-thermal ablation technique that could allow ablation in the pancreas while preserving vital surrounding blood vessels. The aim of this study was to assess the safety and ablation volume of IRE in porcine pancreatic tissue.

METHODS

IRE of swine pancreases was performed using an open technique and ultrasound guidance and the animals were followed for 72 hr, 7 days, and 14 days post-IRE.

RESULTS

All pigs underwent IRE, with one pig was unsuccessful after three attempts using at 3,000 V due to inability to achieve a stable current. All animals recovered well and revealed only mild adhesions, no ascites, and no pancreatic necrosis. All animals had transient increases in amylase and lipase that normalized on post-IRE day 3. Pathologic analysis revealed that ablation defects (median size 3 cm × 2.8 cm) were seen in electroporated areas with significant destruction of the pancreatic tissue with patent vascular structures.

CONCLUSIONS

This animal model demonstrates that IRE of the pancreas performed at an optimal voltage is well tolerated, with rapid resolution of pancreatic inflammation and preservation of vascular structures.

Larger coronary sinus diameter predicts the need for epicardial delivery during mitral isthmus ablation

AIMS

Mitral isthmus ablation is technically challenging, often requiring both endocardial and epicardial coronary sinus (CS) ablation. Blood flow in the CS and circumflex artery may act as a 'heat sink' and reduce the efficacy of radiofrequency ablation. This study investigates how the CS and circumflex artery diameters affect mitral isthmus ablation.

METHODS AND RESULTS

Thirty-five patients underwent ablation for atrial fibrillation. Irrigated-tip catheters were used during mitral isthmus ablation with the following settings: endocardial surface (maximum power: 40-50 W at the annular end of line; maximum temperature: 48°C); CS (maximum power: 25-30 W; maximum temperature: 48°C). The absence of block after 10 min of endocardial ablation led to CS ablation for up to 5 min. If there was still no block, further ablation was at the discretion of the physician. Coronary angiography and CS venography were performed and analysed with quantitative coronary angiography. Mitral isthmus block was achieved in 31 patients (89%). Twenty-three patients (74%) required CS ablation to achieve block. These patients were found to have significantly larger CS diameters (6.5 ± 1.2 vs. 5.4 ± 0.5 mm, P< 0.02). Coronary sinus diameter >59 mm predicted the need for CS ablation (specificity: 100%; sensitivity: 78%). Coronary sinus diameter correlated significantly with total mitral isthmus ablation time (r = 0.52, P < 0.003) and CS ablation time (r = 0.59, P < 0.0005), whereas circumflex diameter did not.

CONCLUSION

Larger-diameter CS is associated with a need for CS ablation during mitral isthmus ablation. Coronary sinus but not circumflex diameter was significantly correlated with total and CS ablation time, supporting the hypothesis that the CS but not the circumflex artery acts as a heat sink.

Planning and follow-up after ablation of hepatic tumors: imaging evaluation

CTs or MRIs are essential for preablative therapy planning of hepatic tumors to identify accurate size, number, and location of tumors. Tumors larger than 5 cm and located near the major branches of the portal vein and hepatic vein have a higher potential for incomplete ablation. Postablative imaging studies are needed to determine if the entire tumors are included in the treatment zone to minimize the risk of local tumor recurrences. Complications of ablative therapy can be identified on post-treatment imaging studies.

Multi-functional liposomes having temperature-triggered release and magnetic resonance imaging for tumor-specific chemotherapy

For development of tumor-specific chemotherapy, we designed liposomes with temperature-triggered drug release and magnetic resonance imaging (MRI) functions. We prepared multi-functional liposomes by incorporating thermosensitive poly(2-ethoxy(ethoxyethyl)vinyl ether) chains with a lower critical solution temperatures around 40 °C and polyamidoamine G3 dendron-based lipids having Gd(3+) chelate residues into pegylated liposomes. These stable doxorubicin (DOX)-loaded liposomes retained DOX in their interior below physiological temperature but released DOX immediately at temperatures greater than 40 °C. They exhibited excellent ability to shorten the longitudinal proton relaxation time. When administered intravenously into colon 26 tumor-bearing mice, accumulated liposomes in tumors increased with time, reaching a constant level 8 h after administration by following T(1)-weighted MRI signal intensity in tumors. Liposome size affected the liposome accumulation efficiency in tumors: liposomes of about 100 nm diameter were accumulated more efficiently than those with about 50 nm diameter. Tumor size also affected accumulation: more efficient accumulation occurred in larger tumors. Tumor growth was strongly suppressed when liposomes loaded with DOX were administered intravenously into tumor-bearing mice and the tumor was heated mildly at 44 °C for 10 min at 8 h after administration. Multi-functional liposomes having temperature-triggered drug release and MRI functions might engender personalized chemotherapy, providing efficient patient-optimized chemotherapy.

The safety and efficacy of ablative techniques adjacent to the hepatic vasculature and biliary system

Ablative techniques may provide an alternative to resection in treating awkwardly placed hepatic malignancy adjacent to major vascular and biliary structures. The heat-sink effect may reduce efficacy adjacent to major vascular structures. Vascular occlusion improves efficacy but is associated with increased vascular and biliary complications. The safety and efficacy of ablation in these situations remain to be defined. Further studies comparing both safety and efficacy are needed.

Temperature-dependent electrode repositioning for multiple overlapping radiofrequency ablation in ex vivo porcine livers

PURPOSE

Overlapping ablations can be used to increase radiofrequency ablation volume. Our goal was to determine, in a porcine model, the relationship of ablation size and temperature for single ablation, and to compare the extent of necrosis resulting from temperature-dependent electrode positioning versus fixed-distance dual ablation.

MATERIALS AND METHODS

The experiments were performed in two parts (single and dual ablations). During single ablation in ex vivo porcine livers, maximum necrotic diameter was compared with the diameters at the level at which temperatures reached 60°C, 55°C, and 50°C. Dual ablations were performed using 60°C (group 60C), 55°C (group 55C), and 50°C (group 50C), and distances of 3 cm (group 3cm) and 4.1cm (group 4.1cm) as the starting point (RFA2-start) for the second ablation.

RESULTS

The maximum necrotic diameter (3.3 ± 0.6 cm) and the necrotic diameters reached at 60°C (2.8 ± 0.8 cm) and 55°C (2.2 ± 0.7 cm) were significantly greater than that at 50°C (0.9 ± 0.5cm; P < .05). In dual ablations, there was no difference between RFA2-start and the maximum diameter of the preceding and subsequent ablations in all temperature-dependent dual ablations (groups 60C, 55C, and 50C) and in group 3cm. (P > .05) However, there was a significant difference between RFA2-start and maximum diameter of the preceding and subsequent ablations in Group 4.1cm (P = .038), resulting in dumbbell-shaped necrosis.

CONCLUSIONS

The necrotic diameter proportionally decreases with the temperature in single ablation. Withdrawing the electrode up to 50° or by 3 cm before reablating results in fusion of the two ablation zones versus withdrawal of 4.1 cm, which results in incomplete necrosis in between two ablation zones.

Radiofrequency ablation of the liver: extended effect of transcatheter arterial embolization with iodized oil and gelatin sponge on histopathologic changes during follow-up in a pig model

PURPOSE

To assess the extended effects of transcatheter arterial embolization with iodized oil and gelatin sponge on liver histopathologic changes in radiofrequency (RF)-ablated zones and the surrounding liver parenchyma in a pig model.

MATERIALS AND METHODS

Eighteen consecutive pigs subjected to 36 RF applications performed immediately after segmental embolization with iodized oil and gelatin sponge to the left lobe of the liver (embolization/RF ablation) were euthanized immediately after the procedure or 1 or 4 weeks later. The right lobes were used as controls for RF applications without embolization. The ablated zones and the surrounding liver parenchyma were measured and examined histopathologically.

RESULTS

The average maximum ablated zone was significantly larger in the embolization/RF ablation specimens than in the RF ablation-alone specimens at all three follow-up time points. Ten of the 12 specimens obtained immediately after embolization/RF ablation showed wide hemorrhagic areas spreading to the periphery of the liver and microscopically showed marked intralobular congestion with sinusoidal dilation. This hemorrhagic change had disappeared in all the specimens obtained 1 week after embolization/RF ablation, but 10 of the 12 specimens showed wedge-shaped areas of segmental degenerative parenchyma beginning at the ablated zone and extending to the periphery of the liver; these were microscopically revealed to be areas of coagulative necrosis, indicating hepatic infarction. The sizes of these necrotic zones had decreased at 4 weeks after embolization/RF ablation.

CONCLUSIONS

RF ablation performed immediately after embolization in normal pig liver induced large ablated zones accompanied by wedge-shaped areas of segmental infarction.

Radioablation settings affecting the size of lesions created ex vivo in porcine livers with monopolar perfusion electrodes

RATIONALE AND OBJECTIVES

To explore the morphological characteristics of ablated lesions and find which combination of duration, temperature, and power was preferable to create largest lesion size with monopolar perfusion electrodes.

MATERIALS AND METHODS

Using monopolar perfusion electrodes to create 72 lesions in 30 excised porcine livers with radiofrequency radiation at different durations (5, 10, 15, and 20 minutes), temperatures (83 degrees C, 93 degrees C, 103 degrees C, and 113 degrees C), and powers (20, 30, and 40 W). Lesion volumes were calculated from longitudinal diameters and transverse diameters. Morphological characteristics were assessed microscopically from slides stained with hematoxylin and eosin.

RESULTS

Positive correlations were found between duration and longitudinal diameter (r = 0.66; P < .001), transverse diameter (r = 0.66; P < .001), distance of ablation beyond the electrode tip (r = 0.56; P < .001), and volume of lesions (r = 0.66; P < .001). Temperature was also positively correlated with longitudinal diameter (r = 0.70; P < .001), transverse diameter (r = 0.72; P < .001), distance of ablation beyond the electrode tip (r = 0.61; P < .001), and lesion volume (r = 0.711; P < .001). Lesion size did not increase when duration was longer than 15 minutes and temperature was higher than 103 degrees C. Power was not correlated with lesion size. Lesion size did not increase with increasing power. Macroscopically, all lesions were elliptical in cross section and appeared three zones: a central zone (I), a coagulated necrotic zone (II), and a hemorrhagic and edematous zone (III) from inside to outside. Microscopically, cells morphology and the nucleus were irregular or even disappeared in zone I. In zone II and III, cells did not appear deformation.

CONCLUSION

Duration and temperature, not power, affected lesion size. The largest lesion size was about 3.5 cm x 2.5 cm x 2.5 cm as temperature and duration was 15 minutes/103 degrees C.

Imaging to optimize liver tumor ablation

Surgical resection remains the ideal treatment for hepatocellular carcinoma and metastasis to the liver. Many alternatives are available for treatment of nonsurgical candidates. Regardless of treatment, optimizing imaging in the pretreatment, treatment and post-treatment settings is critical in order to lower the rates of local tumor progression and maximize the effectiveness of treatment that may result in prolonged survival. This article summarizes some basic imaging techniques of primary and metastatic liver tumors with a focus on how to optimize their treatment with ablation.

Pathomorphological changes after radiofrequency ablation in the liver

Radiofrequency ablation (RFA) has become a widespread treatment option for liver carcinoma. There is limited knowledge regarding the macroscopic and histomorphological changes of induced lesions. Twelve domestic pigs underwent RFA using a Starburst XL device with ablation diameter of 3 cm. One animal died within 24 h, two animals were killed after 2 weeks, and nine after 4 weeks. Their livers were used for macroscopic and histological investigation. Six human liver resection specimens after previous treatment with RFA were also investigated. In pig samples, acute RFA change showed a necrosis zone demarcated by resorption zone with granulocytes and hyperemia. In subchronic and chronic RFA change, the zone of thermofixation was followed by a fibrous capsule and a liver reaction zone. Small blood vessels in the lesions showed damage involving endothelial destruction and thrombosis. Larger vessels within the lesions were observed with intact vessel walls, surrounded by a rim of vital hepatocytes. In the human samples, tumor-infiltrating lymphocytes were reduced (CD3+ cells: 8.4 +/- 3.7/10 high-power fields (HPF); CD4+ cells: 4.2 +/- 1.9/10 HPF), whereas the number of histiocytes was found to be increased (CD68+ cells: 15.5 +/- 9.02/10 HPF). The recognition of thermofixation and the process of resorption of the RFA lesion is important for the interpretation of biopsies and surgical resection specimens.

Minimally invasive image-guided therapy for inoperable hepatocellular carcinoma: What is the evidence today?

Hepatocellular carcinoma (HCC) is a primary malignant tumor of the liver that accounts for an important health problem worldwide. Only 10-15% of HCC patients are suitable candidates for hepatic resection and liver transplantation due to the advanced stage of the disease at time of diagnosis and shortage of donors. Therefore, several minimally invasive image-guided therapies for locoregional treatment have been developed. Tumor ablative techniques are either based on thermal tumor destruction, as in radiofrequency ablation, cryoablation, microwave ablation, laser ablation and high-intensity focused ultrasound, or chemical tumor destruction, as in percutaneous ethanol injection. Image-guided catheter-based techniques rely on intra-arterial delivery of embolic, chemoembolic or radioembolic agents. These minimally invasive image-guided therapies have revolutionized the management of inoperable HCC. This review provides a description of all minimally invasive image-guided therapies currently available, an up-to-date overview of the scientific evidence for their clinical use, and thoughts for future directions.

Comparison of efficacy and toxicity of short-course carbon ion radiotherapy for hepatocellular carcinoma depending on their proximity to the porta hepatis

BACKGROUND AND PURPOSE

To compare the efficacy and toxicity of short-course carbon ion radiotherapy (C-ion RT) for patients with hepatocellular carcinoma (HCC) in terms of tumor location: adjacent to the porta hepatis or not.

MATERIALS AND METHODS

The study consisted of 64 patients undergoing C-ion RT of 52.8 GyE in four fractions between April 2000 and March 2003. Of these patients, 18 had HCC located within 2 cm of the main portal vein (porta hepatis group) and 46 patients had HCC far from the porta hepatis (non-porta hepatis group). We compared local control, survival, and adverse events between the two groups.

RESULTS

The 5-year overall survival and local control rates were 22.2% and 87.8% in the porta hepatis group and 34.8% and 95.7% in the non-porta hepatis group, respectively. There were no significant differences (P=0.252, P=0.306, respectively). Further, there were no significant differences in toxicities. Biliary stricture associated with C-ion RT did not occur.

CONCLUSIONS

Excellent local control was obtained independent of tumor location. The short-course C-ion RT of 52.8 GyE in four fractions appears to be an effective and safe treatment modality in the porta hepatis group just as in the non-porta hepatis group.

Evaluation of Robotic Needle Steering in ex vivo Tissue

Insertion velocity, tip asymmetry, and shaft diameter may influence steerable needle insertion paths in soft tissue. In this paper we examine the effects of these variables on needle paths in ex vivo goat liver, and demonstrate practical applications of robotic needle steering for ablation, biopsy, and brachytherapy. All experiments were performed using a new portable needle steering robot that steers asymmetric-tip needles under fluoroscopic imaging. For bevel-tip needles, we found that larger diameter needles resulted in less curvature, i.e. less steerability, confirming previous experiments in artificial tissue. The needles steered with radii of curvature ranging from 3:4 cm (for the most steerable pre-bent needle) to 2:97m (for the least steerable bevel needle). Pre-bend angle significantly affected needle curvature, but bevel angle did not. We hypothesize that biological tissue characteristics such as inhomogeneity and viscoelasticity significantly increase path variability. These results underscore the need for closed-loop image guidance for needle steering in biological tissues with complex internal structure.

Algorithm optimization for multitined radiofrequency ablation: comparative study in ex vivo and in vivo bovine liver

PURPOSE

To prospectively optimize multistep algorithms for largest available multitined radiofrequency (RF) electrode system in ex vivo and in vivo tissues, to determine best energy parameters to achieve large predictable target sizes of coagulation, and to compare these algorithms with manufacturer's recommended algorithms.

MATERIALS AND METHODS

Institutional animal care and use committee approval was obtained for the in vivo portion of this study. Ablation (n = 473) was performed in ex vivo bovine liver; final tine extension was 5-7 cm. Variables in stepped-deployment RF algorithm were interrogated and included initial current ramping to 105 degrees C (1 degrees C/0.5-5.0 sec), the number of sequential tine extensions (2-7 cm), and duration of application (4-12 minutes) for final two to three tine extensions. Optimal parameters to achieve 5-7 cm of coagulation were compared with recommended algorithms. Optimal settings for 5- and 6-cm final tine extensions were confirmed in in vivo perfused bovine liver (n = 14). Multivariate analysis of variance and/or paired t tests were used.

RESULTS

Mean RF ablation zones of 5.1 cm +/- 0.2 (standard deviation), 6.3 cm +/- 0.4, and 7 cm +/- 0.3 were achieved with 5-, 6-, and 7-cm final tine extensions in a mean of 19.5 min +/- 0.5, 27.9 min +/- 6, and 37.1 min +/- 2.3, respectively, at optimal settings. With these algorithms, size of ablation at 6- and 7-cm tine extension significantly increased from mean of 5.4 cm +/- 0.4 and 6.1 cm +/- 0.6 (manufacturer's algorithms) (P <.05, both comparisons); two recommended tine extensions were eliminated. In vivo confirmation produced mean diameter in specified time: 5.5 cm +/- 0.4 in 18.5 min +/- 0.5 (5-cm extensions) and 5.7 cm +/- 0.2 in 21.2 min +/- 0.6 (6-cm extensions).

CONCLUSION

Large zones of coagulation of 5-7 cm can be created with optimized RF algorithms that help reduce number of tine extensions compared with manufacturer's recommendations. Such algorithms are likely to facilitate the utility of these devices for RF ablation of focal tumors in clinical practice.

Thermal ablation for unresectable liver tumours, time to move forward?

Even with the advent of laparoscopic techniques for liver tumours, classic resections still represent a major undertaking for numerous liver lesions. The avoidance of surgery using ablative techniques has been the aim for over 20 years. Large volumes can now be rapidly treated with low morbidity with the many technical developments and modifications of the delivery probes. Despite these advances recurrences rates remain high with all of the presently available techniques. The biological and pathophysiological basis underlying may help explain their limitations and are important in understanding where they may be appropriately applied and ways in which they may be improved in the future.

Hip fracture after radiofrequency ablation therapy for bone tumors: two case reports

Radiofrequency ablation (RFA) has become a valuable therapeutic modality in cancer treatment over the last decade. In orthopedic surgery, RFA is used for the treatment of benign bone tumors and bone metastases. Complications are rare and, to our knowledge, bone fracture as a complication due solely to RFA has not been reported to date. In this report we describe two patients with a fracture in the calcar region of the femur as a complication of RFA treatment for bone malignancies. Since RFA is applied increasingly often, it is important to report this risk of fracture as a complication of treatment of lesions in the femoral calcar.

Radiofrequency ablation induces dedifferentiation of hepatocellular carcinoma

Radiofrequency ablation (RFA) has been reported to be a minimally invasive and effective procedure for the treatment of hepatocellular carcinoma (HCC). However, the pattern of recurrence and complications following RFA have yet to be fully identified. During the period January 2000 to December 2006, we performed HCC resections in 15 patients who developed local recurrence after RFA, as well as in 144 patients without RFA. In patients with local recurrence of HCC after RFA, the tumors showed a more invasive growth, more vascular invasion and less differentiation compared with tumors of patients without RFA. In 6 of the 15 patients with recurrence after RFA, needle biopsy of the HCC was performed before tumor ablation. In five of these 6 patients, dedifferentiation of the tumor was observed. These findings suggest that heat shock due to RFA induces dedifferentiation of HCC. Recurrence after RFA may result in an aggressive tumor that precludes any possibility of cure. RFA must not be considered a suitable alternative to surgery in patients with a low surgical risk. Instead, RFA should be performed according to strict indications by skilled operators using the latest devices.