Radiofrequency Ablation for Hepatocellular Carcinoma: A Prospective Comparison of Four Radiofrequency Devices

Ablative and non-surgical therapies for early and very early hepatocellular carcinoma: a systematic review and network meta-analysis

Background

A wide range of ablative and non-surgical therapies are available for treating small hepatocellular carcinoma in patients with very early or early-stage disease and preserved liver function.

Objective

To review and compare the effectiveness of all current ablative and non-surgical therapies for patients with small hepatocellular carcinoma (≤ 3 cm).

Design

Systematic review and network meta-analysis.

Data sources

Nine databases (March 2021), two trial registries (April 2021) and reference lists of relevant systematic reviews.

Review methods

Eligible studies were randomised controlled trials of ablative and non-surgical therapies, versus any comparator, for small hepatocellular carcinoma. Randomised controlled trials were quality assessed using the Cochrane Risk of Bias 2 tool and mapped. The comparative effectiveness of therapies was assessed using network meta-analysis. A threshold analysis was used to identify which comparisons were sensitive to potential changes in the evidence. Where comparisons based on randomised controlled trial evidence were not robust or no randomised controlled trials were identified, a targeted systematic review of non-randomised, prospective comparative studies provided additional data for repeat network meta-analysis and threshold analysis. The feasibility of undertaking economic modelling was explored. A workshop with patients and clinicians was held to discuss the findings and identify key priorities for future research.

Results

Thirty-seven randomised controlled trials (with over 3700 relevant patients) were included in the review. The majority were conducted in China or Japan and most had a high risk of bias or some risk of bias concerns. The results of the network meta-analysis were uncertain for most comparisons. There was evidence that percutaneous ethanol injection is inferior to radiofrequency ablation for overall survival (hazard ratio 1.45, 95% credible interval 1.16 to 1.82), progression-free survival (hazard ratio 1.36, 95% credible interval 1.11 to 1.67), overall recurrence (relative risk 1.19, 95% credible interval 1.02 to 1.39) and local recurrence (relative risk 1.80, 95% credible interval 1.19 to 2.71). Percutaneous acid injection was also inferior to radiofrequency ablation for progression-free survival (hazard ratio 1.63, 95% credible interval 1.05 to 2.51). Threshold analysis showed that further evidence could plausibly change the result for some comparisons. Fourteen eligible non-randomised studies were identified (n ≥ 2316); twelve had a high risk of bias so were not included in updated network meta-analyses. Additional non-randomised data, made available by a clinical advisor, were also included (n = 303). There remained a high level of uncertainty in treatment rankings after the network meta-analyses were updated. However, the updated analyses suggested that microwave ablation and resection are superior to percutaneous ethanol injection and percutaneous acid injection for some outcomes. Further research on stereotactic ablative radiotherapy was recommended at the workshop, although it is only appropriate for certain patient subgroups, limiting opportunities for adequately powered trials.

Limitations

Many studies were small and of poor quality. No comparative studies were found for some therapies.

Conclusions

The existing evidence base has limitations; the uptake of specific ablative therapies in the United Kingdom appears to be based more on technological advancements and ease of use than strong evidence of clinical effectiveness. However, there is evidence that percutaneous ethanol injection and percutaneous acid injection are inferior to radiofrequency ablation, microwave ablation and resection.

Study registration

PROSPERO CRD42020221357.

Funding

This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment (HTA) programme (NIHR award ref: NIHR131224) and is published in full in Health Technology Assessment; Vol. 27, No. 29. See the NIHR Funding and Awards website for further award information.

Percutaneous Radiofrequency Ablation With a Multiple-Electrode Switching System for Medium-Sized Hepatocellular Carcinomas

Objective

This study aimed to retrospectively evaluate the safety and short-term therapeutic efficacy of radiofrequency ablation (RFA) with a multiple-electrode switching system (MESS) to treat medium-sized (3.1–5.0 cm) hepatocellular carcinomas (HCCs).

Summary of Background Data

Conventional monopolar RFA is limited in achieving local control for tumors larger than 3 cm. Therefore, MESS-RFA was developed, and it can create a sufficiently large ablation volume, including the target tumor and a 5- to 10-mm safety margin in medium-sized tumors.

Methods

We performed a total of 168 RFAs with a MESS for 166 patients. The patients were treated under ultrasonographic guidance by a percutaneous switching system RFA with a multichannel RF generator and 2 or 3 internally cooled electrodes. Technical effectiveness, local progression, and remote recurrence of HCC were determined.

Results

For the 166 isolated HCC tumors, the complete ablation rate of MESS-RFA was 98.79% (164 of 166). Mean ablation time per procedure was 12.33 ± 3.01 minutes; mean ablation diameter was 5.79 ± 0.61 cm. The complication rate was 2.41%. During follow-up (averaging 16.54 months), local tumor progression occurred in 15 of 166 patients (9.03%) with technical effectiveness, whereas new HCCs were detected in 40 of 166 patients (24.09%). Multivariate analyses revealed that local tumor progression was only associated with serum α-fetoprotein levels above 100 ng/mL as a risk factor.

Conclusion

MESS-RFA for achieving sufficient ablation volume is safe and efficient. This method also showed relatively successful therapeutic effectiveness on short-term follow-up in the treatment of medium-sized HCCs.

The Role of a Curved Electrode with Controllable Direction in the Radiofrequency Ablation of Liver Tumors Behind Large Vessels

PURPOSE

To investigate the role of a novel curved radiofrequency ablation (RFA) electrode with controllable direction in the ablation of tumors behind large hepatic vessels in ex vivo bovine and in vivo canine liver experiments.

MATERIALS AND METHODS

Approval from the institutional animal care and use committee was obtained. In ex vivo experiments, conventional multi-tines expandable electrodes, conventional monopolar straight electrodes and novel curved electrodes were used in the ablation of the bovine liver (n = 90). The ablated area, parallel axis, vertical axis and shape of different electrodes were compared. Then, 24 beagle dogs (10 months old, female) were used for in vivo experiments. Visual tumor targets deeply located in the portal vein were established, and ultrasound-guided liver ablation was performed with different electrodes. The ablation range, target coverage rate, percentage of normal tissue injury and damage to adjacent vessels were evaluated. The Kruskal-Wallis test and the Chi-squared test were used for statistical analysis.

RESULTS

For the ex vivo study with a 3-cm electrode, the ablation area of the multi-tines expandable electrode group (7.14 ± 0.16 cm2) was significantly larger than that of the novel curved electrode group (5.01 ± 0.30 cm2, P < 0.001) and the monopolar straight electrode group (5.43 ± 0.15 cm2, P < 0.001). The results obtained with the 4-cm electrode in the three groups were in accordance with those of the 3-cm electrode. In vivo, the normal tissue damage area of the novel curved electrode group was smaller than that of the multi-tines expandable electrode group (1.10 ± 0.18 cm2 vs. 4.00 ± 0.18 cm2, P < 0.001). The target coverage rate of the novel curved electrode group was better than that of the monopolar straight electrode group (100% vs. 80.86 ± 1.68%, P < 0.001). The hematoxylin and eosin (H&E) and TUNEL staining results showed that the ablation necrosis area was adjacent to large vessels, but the vascular wall was not significantly damaged in the novel curved electrode group.

CONCLUSION

Our preliminary results showed that the novel curved RFA electrode with controllable direction could achieve accurate ablation for tumors behind large hepatic vessels, with a better target coverage rate and less damage to normal tissue, than conventional multi-tines expandable electrodes and monopolar straight electrodes.

Early complications after percutaneous radiofrequency ablation for hepatocellular carcinoma: an analysis of 1,843 ablations in 1,211 patients in a single centre: experience over 10 years

AIM

To evaluate the incidence of adverse events and associated factors after radiofrequency ablation (RFA) in patients with hepatocellular carcinoma within 30 days.

MATERIALS AND METHODS

The early complications that occurred within 30 days after RFA at a single institution from January 2000 to July 2010 were reviewed in order to evaluate the morbidity, mortality, and risk factors associated with the complications. In total, 1,211 patients (845 men, 70.5%) with a mean age of 68 years (range, 27-88 years) underwent 1,843 RFA procedures.

RESULTS

The overall incidence rate of complications was 6.8% (125 cases). Major complications (n=36, 2%) included liver abscess (n=15, 0.8%), intraperitoneal bleeding (n=8, 0.4%), liver failure (n=5, 0.3%), variceal bleeding (n=3, 0.2%), haemothorax (n=2, 0.1%), cholecystitis (n=2, 0.1%), and bowel perforation (n=1, 0.1%). Among the minor complications (n=89, 4.8%), the most common was the post RFA syndrome accompanied by pain and fever (n=75, 4.1%). Other minor complications included significant pleural effusion (n=7, 0.4%), skin wound infection (n=4, 0.2%), and thermal injuries to the skin (n=3, 0.2%). Procedural infections significantly increased with tumour size (OR=1.379; 95% confidence interval [CI], 1.191-1.579; p<0.001), and multiple overlapping ablations (OR=1.118; 95% CI, 1.019-1.227, p=0.018). Thrombocytopenia (<50,000/μl), prothrombin time, and serum albumin level were significantly associated with post-RFA bleeding episodes (p=0.041, p=0.021, and p=0.003, respectively). The overall mortality rate was 0.3% (three cases of hepatic failure, two case of sepsis, and one case of renal failure).

CONCLUSIONS

RFA is a safe and effective local treatment for hepatocellular carcinoma. Careful selection of patients and appropriate RFA planning could decrease procedural mortality and morbidity.

Irreversible electroporation ablation: creation of large-volume ablation zones in in vivo porcine liver with four-electrode arrays

PURPOSE

To prospectively determine optimal parameters with which to achieve defined large target zones of coagulation by using irreversible electroporation (IRE) with four-electrode arrays and the time needed to achieve this treatment effect in an in vivo animal model.

MATERIALS AND METHODS

This study was approved by the animal care and use committee. Ultrasonography (US)-guided IRE ablation (n = 90) was performed in vivo in 69 pig livers with an array of four electrodes (18 gauge) and an electroporation generator. Cardiac-gated 100-µsec IRE pulses were applied sequentially between the six sets of electrode pairs at 2250-3000 V. Multiple algorithms of energy deposition and electrode configuration were studied, including interelectrode spacing (1.5-2.5 cm), number of IRE pulses applied consecutively to each electrode pair (10, 20, 50, and 100), and number of times per cycle each electrode pair was activated (one to 10). Resultant zones of treatment were measured with US 1.5-3 hours after IRE and confirmed at gross and histopathologic examination. Data and ablation times were compared to determine the optimal algorithms with which to achieve 4-7-cm areas of treatment effect in the shortest time possible. In addition, the IRE current applied was correlated with ablation size. Data were analyzed by using analysis of variance with multiple comparisons, t tests, or nonparametric statistics.

RESULTS

For 2.5-cm spacing, ablation diameter was increased by increasing either the overall time of energy application or the number of cycles of 20 pulses (P < .01 for both). IRE application of less than four cycles (or continuous IRE application of 100 pulses) did not result in contiguous ablation. However, sequentially increasing the number of cycles of IRE from four to 10 increased both the electrical current applied (from 14.4 A ± 0.4 to 17.6 A ± 0.7, P = .0004) and ablation diameter (from 5.6 cm ± 0.3 to 6.6 cm ± 0.3, P = .001). Although division of application into cycles did not alter coagulation at 2.0- and 1.5-cm spacing, application of energy to diagonal electrode pairs increased coagulation. Thus, one 100-pulse cycle (11.0 minutes ± 1.4) produced 4.8 cm ± 0.3 of ablation for 2.0-cm spacing with diagonal pairs but only 4.1 cm ± 0.3 of ablation without diagonal pairs (7.5 minutes ± 1.0, P < .03 for both).

CONCLUSION

With four-electrode arrays, IRE can create large contiguous zones of treatment effect in clinically acceptable ablation times; parameters can be tailored to achieve a wide range of ablation sizes. Cyclical deposition of IRE application is beneficial, particularly for larger interprobe spacing, most likely owing to alterations of electrical conductivity that occur after successive applications of IRE energy.

Local ablation for hepatocellular carcinoma in taiwan

Hepatocellular carcinoma (HCC) is the second commonest cancer in Taiwan. The national surveillance program can detect HCC in its early stages, and various curative modalities (including surgical resection, orthotopic liver transplantation, and local ablation) are employed for the treatment of small HCC. Local ablation therapies are currently advocated for early-stage HCC that is unresectable because of co-morbidities, the need to preserve liver function, or refusal of resection. Among the various local ablation therapies, the most commonly used modalities include percutaneous ethanol injection and radiofrequency ablation (RFA); percutaneous acetic acid injection and microwave ablation are used less often. RFA is more commonly employed than other local ablative modalities in Taiwan because the technique is highly effective, minimally invasive, and requires fewer sessions. RFA is therefore advocated in Taiwan as the first-line curative therapy for unresectable HCC or even for resectable HCC. However, current RFA procedures are less effective against tumors that are in high-risk or difficult-to-ablate locations, are poorly visualized on ultrasonography (US), or are large. Recent advancements in RFA in Taiwan can resolve these issues by the creation of artificial ascites or pleural effusion, application of real-time virtual US assistance, use of combination therapy before RFA, or use of switching RF controllers with multiple electrodes. This review article provides updates on the clinical outcomes and advances in local ablative modalities (mostly RFA) for HCC in Taiwan.

Small- and medium-sized hepatocellular carcinomas: monopolar radiofrequency ablation with a multiple-electrode switching system-mid-term results

PURPOSE

To prospectively assess the safety and mid-term therapeutic effectiveness of monopolar radiofrequency (RF) ablation with a multiple-electrode switching system for treating small- and medium-sized (≤ 5 cm) hepatocellular carcinomas (HCCs).

MATERIALS AND METHODS

The institutional review board approved this prospective study, and all patients gave informed consent. From February 2009 to January 2010, 166 patients (110 men and 56 women; age range, 38-86 years; mean age, 62 years ± 10 [standard deviation]) with 166 HCCs less than or equal to 5 cm in diameter were treated with monopolar RF ablation with a multiple-electrode switching system. One of three experienced radiologists performed the RF ablation. Technique effectiveness, ablation volume and time, and major complications were evaluated by means of computed tomography (CT) immediately after RF ablation and at follow-up CT examinations at 1 month and then every 3 months after the procedure. The overall survival, disease-free survival, and local tumor progression-free survival rates were evaluated by using the Kaplan-Meier method.

RESULTS

The technique effectiveness rate determined 1 month after RF ablation was 99.4%. Mean ablation parameters were as follows: volume, 85 cm(3) ± 54; maximum diameter, 61 mm ± 13; and minimum diameter, 43 mm ± 11. The major complication rate was 4.8%. The 6-month and 1-, 2-, and 3-year local tumor progression rates were 2%, 6%, 10%, and 11%, respectively. The overall survival rates at 1, 2, and 3 years after RF ablation were 99%, 97%, and 96%, and corresponding local tumor progression-free survival rates were 94%, 90%, and 89%, respectively. The disease-free survival rates at 1, 2, and 3 years after RF ablation were 75%, 60%, and 54%, respectively.

CONCLUSION

Monopolar RF ablation with a multiple-electrode switching system in small- and medium-sized HCCs was safe and efficient, and it provided successful local tumor control and high local tumor progression-free survival rates because an adequate ablation volume was obtained.

Complications of radiofrequency ablation for hepatocellular carcinoma in a multicenter study: An analysis of 16 346 treated nodules in 13 283 patients

AIM

  We surveyed multiple centers to identify types and frequency of complications and mortality rate associated with radiofrequency ablation (RFA) of hepatocellular carcinoma (HCC).

METHODS

  We distributed a questionnaire developed by members of the Chugoku-Shikoku Society for the Local Ablation Therapy of Hepatocellular Carcinoma to 20 centers and analyzed types and frequency of complications and mortality rate.

RESULTS

  In total, 16 346 nodules were treated in 13 283 patients between January 1999 and November 2010. Five patients (0.038%) died: two from intraperitoneal hemorrhage, and one each from hemothorax, severe acute pancreatitis and perforation of the colon. In 16 346 treated nodules, 579 complications (3.54%) were observed, including 78 hemorrhages (0.477%), 276 hepatic injuries (1.69%), 113 extrahepatic organ injuries (0.691%) and 27 tumor progressions (0.17%). The centers that treated a large number of nodules and performed RFA modifications, such as use of artificial ascites, artificial pleural effusion and bile duct cooling, had low complication rates.

CONCLUSION

  This study confirmed that RFA is a low-risk treatment for HCC and that sufficient experience and technical skill can reduce complications.

Ablative therapies in adrenal tumors: primary and metastatic

A large number of adrenal tumors are now identified either incidentally or associated with a metastatic workup for cancer. While the vast majority of these lesions are benign, those that prove to be primary or secondary cancers are traditionally treated with surgical resection. A wide variety of alternative, less invasive therapies exist. One of these, thermal ablation, is examined herein.

Bimodal electric tissue ablation (BETA)--effect of reversing the polarity of the direct current on the size of ablation

BACKGROUND

Bimodal electric tissue ablation (BETA) is a new technique that uses the direct current in electrolysis to improve the efficacy of radio frequency (RF) ablation. It was hypothesized that attaching the cathode of the electrolytic circuit to the RF electrode will increase the tissue hydration, therefore delaying tissue desiccation during ablation. Consequently, the ablation process can continue for a longer period of time and produce larger ablations. This hypothesis was tested by reversing the polarity of the electrolytic circuit, which theoretically would cause tissue desiccation and therefore produce smaller ablations. This new setup is called reversed polarity bimodal electric ablation (RP-BEA).

MATERIALS AND METHODS

Three types of ablations standard radiofrequency ablation (RFA), BETA, and RP-BEA) were tested in a pig liver model. In BETA and RP-BEA, 9 V of direct current were provided for 10 min, after which the rf generator were switched on and both electrical circuits allowed to run concurrently. In all three setups, ablations were continued until "roll-off." The size of ablation was measured and compared with each other.

RESULTS

The duration of ablation was significantly shorted in RP-BEA compared with standard RFA and BETA (48 s verus 148 s and 84 s, respectively, P = 0.004). The sizes of ablations in RP-BEA were also significantly smaller compared with standard RFA and BETA-skin.

CONCLUSION

RP-BEA caused tissue desiccation resulting in a shorter duration of ablation and smaller ablations. Therefore, the theory that BETA increases ablation size due to the effects of increased tissue hydration around the rf electrode is correct.

Systematic review and meta-analysis of survival and disease recurrence after radiofrequency ablation for hepatocellular carcinoma

BACKGROUND

Despite being one of the commonest causes of cancer-related death around the world, only 20 per cent of hepatocellular carcinomas (HCCs) are amenable to curative treatment (surgical resection or liver transplantation). Radiofrequency ablation (RFA) has emerged as a popular therapy for unresectable HCC. There is evidence that the disparity in survival after curative RFA and surgery for HCC, especially tumours smaller than 3 cm in diameter, is narrowing. This review examined the survival and disease recurrence rates after RFA for HCC over the past decade.

METHODS

A systematic review was conducted using MEDLINE, Embase, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Cochrane Methodology Register and the Database of Abstracts of Reviews of Effects from January 2000 until November 2010. Papers reporting on patients with HCC who were treated with RFA, either in comparison or in combination with other interventions, such as surgery or percutaneous ethanol injection (PEI), were eligible for inclusion. Outcome data collected were overall survival, disease-free survival and disease recurrence rates. Only randomized controlled trials (RCTs), quasi-RCTs and non-randomized comparative studies with more than 12 months' follow-up were included.

RESULTS

Forty-three articles, including 12 RCTs, were included in the review. The majority of the articles reported the use of RFA for unresectable HCC, often in combination with other treatments such as PEI, transarterial chemoembolization and/or surgery. Overall and disease-free survival rates continue to improve, despite an increase in the size and numbers of tumours treated. More recently some clinicians have used RFA to treat selected patients with resectable HCC, with good outcomes.

CONCLUSION

RFA provides a valuable treatment option for patients with unresectable HCC. It improves survival in those previously considered to have advanced disease. As progress continues to be made, RFA is gradually being used to treat resectable HCC.

Radiofrequency ablation of hepatocellular carcinoma

Radiofrequency ablation (RFA), usually performed under percutaneous ultrasound guidance, is considered the gold standard among minimally invasive therapies. On the strength of some recent randomized trials, its indications include operable patients with small hepatocellular carcinoma and inoperable patients with more advanced disease also in combination with other therapies. RFA has lower complication rates and costs less than surgery.

Stereotactic radiofrequency ablation (SRFA) of liver lesions: technique effectiveness, safety, and interoperator performance

PURPOSE

To evaluate technique effectiveness, safety, and interoperator performance of stereotactic radiofrequency ablation (SRFA) of liver lesions.

METHODS

Retrospective review including 90 consecutive patients from January 2008 to January 2010 with 106 computed tomography-guided SRFA sessions using both single and multiple electrodes for the treatment of 177 lesions: 72 hepatocellular carcinoma (HCC) and 105 metastases with a mean size of 2.9 cm (range 0.5-11 cm). Technique effectiveness and 1-year local recurrence were evaluated by computed tomographic scans. Complications, mortality, and hospital days were recorded. The performance between an experienced and inexperienced interventional radiologist was compared.

RESULTS

The overall technique effectiveness after a single SRFA was 95.5% (93.1% for HCC and 97.1% for metastases). Four of the eight unsuccessfully treated lesions could be retreated (secondary technique effectiveness of 97.7%). Local recurrence at 1 year was 2.9%. Technique effectiveness was significantly different for lesions<5 cm (96.7%) and >5 cm (87.5%) (P=0.044) but not for lesions<3 cm (95.9%) and 3-5 cm (100%). Compared to clear parenchymal property (97.3%), vessel vicinity (93.3%) (P=0.349) and subcapsular (95.2%) (P=0.532) had no, but hollow viscera vicinity (83.3%) had a significantly lower technique effectiveness (P=0.020). Mortality rate was 0.9%. Major complications and hospital days were higher for cirrhosis Child-Pugh B (20%, 7.2 days) than Child-Pugh A (3.1%, 4.7 days) patients and for metastases (5.1%, 4.3 days). There was no significant difference in interoperator performance.

CONCLUSION

SRFA allowed for efficient, reliable, and safe ablation of large-volume liver disease.

Locoregional therapy for hepatocellular carcinoma

Locoregional therapies for hepatocellular carcinoma have progressed greatly in the last 30 years, beginning with the introduction of chemoembolization. Embolization techniques have evolved with the use of drug-eluting beads and radioembolization with yttrium-90. In the last 10 years, several new ablation techniques were developed including radiofrequency ablation, microwave ablation, cryoablation, laser ablation, and irreversible electroporation. Isolated or in combination, these techniques have already shown that they can improve patient survival and/or provide acceptable palliation.

Radiofrequency ablation for hepatocellular carcinoma: use of low vs maximal radiofrequency power

OBJECTIVES

To investigate whether radiofrequency (RF) ablation with low power (LP) or maximal power (MP) for hepatocellular carcinoma (HCC) can achieve optimal ablation and fewer adverse effects.

METHODS

RF ablation was performed with MP in 101 patients (129 tumours) and with LP in 46 patients (61 tumours). MP RF ablation used power of >120 W. RF power below this was designated as LP. Clinical outcomes were also analysed in subgroups of high-risk tumours near the bile duct and blood vessels.

RESULTS

Primary effectiveness was achieved in 91.8% in the LP group and 89.9% in the MP group (p = 0.795). 1 and 2-year local tumour progression rates were 28% and 30%, respectively, in the LP group, and 24% and 29%, respectively, in the MP group (p = 0.70). 1 and 2-year survival rates were 98% and 98%, respectively, in the LP group, and 93% and 90%, respectively, in the MP group (p = 0.216). The MP group had more adverse effects, with post-RF ablation syndrome, asymptomatic pleural effusion and ascites, than the LP group (20% vs 39% in the MP group; p = 0.027); however, there was no significant difference in major complication rates (6% in the MP and LP groups; p = 0.497). Among the patients with high-risk tumours, RF ablation using MP vs LP was comparable in primary effectiveness (91.7% vs 95.2%; p = 0.618), local tumour progression (42.9% vs 29.2%; p = 0.304) and overall complications (5% vs 8%; p=0.618).

CONCLUSION

RF ablation with LP and MP are comparable in clinical outcomes but considerably fewer adverse effects were encountered in the LP group.

Recent advances of radiofrequency ablation for early hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of death in the malignant neoplastic diseases in the world. Surgical operation is sometimes not indicated because of complicated liver cirrhosis and extrahepatic disorders. Radiofrequency ablation has been developed as a less invasive treatment for HCC since 1999, and long-term outcome has been shown. There are several complications which should be paid attention, and to improve the prognosis, combination treatment with transarterial chemoembolization should be discussed. Overall survival after between RFA and surgical resection should be compared prospectively. Establishment of staging system for treatment allocation of HCC and prevention of HCC recurrence is important issue to be examined.

Percutaneous ablation of hepatocellular carcinoma: current status

Hepatocellular carcinoma (HCC) is an increasingly common disease with dismal long-term survival. Percutaneous ablation has gained popularity as a minimally invasive, potentially curative therapy for HCC in nonoperative candidates. The seminal technique of percutaneous ethanol injection has been largely supplanted by newer modalities, including radiofrequency ablation, microwave ablation, cryoablation, and high-intensity focused ultrasound ablation. A review of these modalities, including technical success, survival rates, and complications, will be presented, as well as considerations for treatment planning and follow-up.

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.

Tumour ablation: technical aspects

Image-guided percutaneous radiofrequency ablation (RFA) is a minimally invasive, relatively low-risk procedure for tumour treatment. Local recurrence and survival rates depend on the rate of complete ablation of the entire tumour including a sufficient margin of surrounding healthy tissue. Currently a variety of different RFA devices are available. The interventionalist must be able to predict the configuration and extent of the resulting ablation necrosis. Accurate planning and execution of RFA according to the size and geometry of the tumour is essential. In order to minimize complications, individualized treatment strategies may be necessary for tumours close to vital structures. This review examines the state-of-the art of different device technologies, approaches, and treatment strategies for percutaneous RFA of liver tumours.

Radiofrequency ablation of primary and metastatic lung cancers

Radiofrequency ablation is an accepted method of therapy for unresectable liver cancer. Most recently, interest in using this technology for treatment of primary and metastatic lung tumors has increased. Early animal studies have led to numerous human trials that suggest that radiofrequency ablation can play a major role in treatment of both early-stage primary lung cancer and metastatic lesions. Technical aspects of this therapy as well as areas of further research are discussed.