Radiofrequency ablation followed by resection of malignant liver tumors

Laparoscopic radiofrequency thermal ablation: a new approach to symptomatic uterine myomas

OBJECTIVE

The purpose of this study was to evaluate the feasibility and efficacy of laparoscopic radiofrequency ablation of uterine fibroids.

STUDY DESIGN

Eighteen women with symptomatic intramural uterine myomas underwent radiofrequency ablation under laparoscopic guidance. Postoperative sonographic evaluations of the fibroids size were scheduled at 1, 3, 6 ,9, and 12 months. The impact of myoma-related symptoms on quality of life (QOL) was assessed using a validated questionnaire.

RESULTS

The median number of myomas treated per patient was 1 (1-3). The median baseline volume of the dominant myoma was 67.2 cm 3 (14.8-332.8). No intraoperative or postoperative complications occurred. The median reductions in myomas volume were 41.5%, 59%, and 77% at 1, 3, and 6-months, follow-up evaluation, respectively. No further change in fibroid size was observed at 9 months and 1 year. A significant improvement in the symptoms score and QOL score was observed at 3 and 6 months, follow-up.

CONCLUSION

In this pilot study, laparoscopic radiofrequency ablation successfully reduced fibroid symptoms and fibroid volume in short-term follow-up. Additional studies are needed before its efficacy and safety can be confirmed.

Influence of large intrahepatic blood vessels on the gross and histological characteristics of lesions produced by radiofrequency ablation in a pig liver model

AIMS

To determine whether the presence of large intrahepatic blood vessels (>/=3 mm) affect radiofrequency (RF)-induced coagulation necrosis, the gross and histological characteristics of RF-ablated areas proximal to or around vessels were examined in normal pig livers.

METHODS

An RF ablation treatment using a two-stepwise extension technique produced 12 lesions: six contained vessels (Group A), and the other six were localized around vessels (Group B).

RESULTS

Gross examination revealed that the longest and shortest diameters of the ablated lesions were significantly larger in Group B than in Group A. In Group A, patent vessels contiguous to the lesion were present in a tongue-shaped area, whereas the lesions in Group B were spherical. Staining with nicotinamide adenine dinucleotide diaphorase was negative within the ablated area; but, if vessels were present in the ablated area, the cells around the vessels in an opposite direction to the ablation were stained blue.

CONCLUSIONS

Roll-off can be achieved with 100% cellular destruction within a lesion that does not contain large vessels. The ablated area was decreased in lesions that contained large vessels, suggesting that the presence of large vessels in the ablated area further increases the cooling effect and may require repeated RF ablation treatment to achieve complete coagulation necrosis.

Radiofrequency ablation of liver tumours: systematic review

Thermal ablation by use of radiofrequency energy can be used to achieve necrosis of liver tumours, and increased availability of this technique is leading to more widespread use. Much of the impetus for the use of radiofrequency ablation has come from cohort series that have provided an evidence base for this technique. Here, we give an overview of the current status of radiofrequency ablation for liver tumours, including its physical properties, to assess the characteristics that make this technique applicable in clinical practice. We review the technical development of probe design and summarise current indications and outcomes of reported clinical use. We also provide a profile of side-effects and information on the integration of this technique into the general management of patients with liver tumours. Current evidence suggests that radiofrequency ablation can be done with few side effects; however, although this technique seems to ablate tumours effectively, it should form part of multidisciplinary care for liver cancer. Crucially, the role of radiofrequency ablation in lengthening the survival of patients with liver tumours remains to be assessed.

Pre-transplant treatment of hepatocellular carcinoma: assessment of tumor necrosis in explanted livers

Although liver transplantation (LT) is likely the most effective therapy for localized hepatocellular cancer (HCC), limited donor livers have resulted in prolonged waiting times for transplant. Pre-transplant therapy such as transarterial chemoembolization (TACE), percutaneous ethanol injection (PEI), and radiofrequency ablation (RFA) may be needed to sustain patients who are waiting. Records, imaging studies, and pathology to identify tumor necrosis on 15 explanted livers with HCC were reviewed. Forty-nine nodules were removed from 15 explanted livers. Five nodules in three livers that received no pre-transplant therapy were excluded from the study. Of the remaining 44 nodules in 12 patients, 29 (66%) had 75% or more tumor necrosis. Fifteen nodules in five patients had <75% necrosis and these were due to local/non-local recurrences or perhaps suboptimal treatment with RFA, TACE or cisplatin gel injection. Mean waiting time for LT was 162.5 d. Nine of 13 patients had a different number of nodules when listed as were seen at explant, although stage changed in only three patients. One patient died 48 months post-LT (recurrent HCC), while the remaining patients are alive 2-55 months post-LT. We conclude that pre-transplant treatments for HCC are generally effective in achieving tumor necrosis. Factors involved in eventual extent of HCC seen at LT may include adequacy of treatment, accuracy of imaging techniques, local/non-local recurrences, and time waiting for transplant. We now need to determine if tumor necrosis can allow patients to wait longer for transplant and eventually affect long-term outcome.

CT-Guided Radiofrequency Ablation:A Potential Complementary Therapy for Patients with Unresectable Primary Lung Cancer—A Preliminary Report of 33 Patients

OBJECTIVE

We report our preliminary evaluation of the effectiveness, safety, technical feasibility, and complications of palliative CT-guided radiofrequency ablation of unresectable primary pulmonary malignancies.

SUBJECTS AND METHODS

Thirty-three patients (26 men and seven women; age range, 44-75 years; mean age, 66 years) with unresectable malignant lung neoplasms underwent 35 CT-guided tumor ablation sessions. Follow-up CT was performed 6 months (29 cases) and 1 year (10 cases) after treatment. In 19 patients, these findings were correlated with cytohistopathologic assessment obtained with CT-guided fine-needle aspiration biopsy or core biopsy at 6-month follow-up. Size and CT appearance of the treated lesions were correlated with cytohistologic features and clinical scores.

RESULTS

Thirty-five technically successful radiofrequency ablation treatments were performed. The only complications in the periprocedural period were three cases of minor pneumothorax, five cases of sputum cruentum, and three asymptomatic pleural effusions. Contrast-enhanced CT performed at 6-month follow-up showed four cases of complete and 13 cases of partial lesion ablation, 11 cases of stabilized lesion size, and one case of increased lesion size. Contrast-enhanced CT performed at 1-year follow-up showed unchanged lesion size in six cases and reduction in four cases. Six-month cytohistologic examinations showed total coagulation necrosis in seven lesions and partial necrosis in 12. Clinical improvement in pretreatment symptoms was observed in 12 of 29 patients seen at 6-month follow-up. Eight patients died within 1 year of treatment of non-procedure-related causes.

CONCLUSION

Our experience suggests that radiofrequency ablation can be used successfully in unresectable lung cancer as an alternative or complementary treatment to radio- or chemotherapy. Larger studies are necessary to fully evaluate its potential combination with other treatment techniques.

Radiofrequency ablation of 40 lung neoplasms: preliminary results

OBJECTIVE

Radiofrequency thermal ablation is a minimally invasive treatment widely used for treatment of liver neoplasms and has also been tested on other types of tumor. Few studies have been published regarding the use of radiofrequency thermal ablation in the treatment of lung neoplasms. This study was performed to evaluate the technical feasibility, the safety, and the efficacy of lung radiofrequency thermal ablation.

SUBJECTS AND METHODS

Between February 2002 and March 2003, 18 subjects with unresectable lung neoplasms, four of whom had primary neoplasms and 14 of whom had metastatic neoplasms, underwent lung radiofrequency ablation. The technique was performed percutaneously using a monopolar cooled-tip electrode needle under CT guidance with the patient under general anesthesia. Patients had no more than three nodules with a total diameter of 10 cm and no evidence of extrathoracic disease. A total of 40 nodules were treated in 24 therapeutic sessions. After treatment, patients underwent follow-up every 3 months by CT and nuclear MRI with gadolinium for a median time of 8 months (range, 2-14 months).

RESULTS

No evidence of local relapse was discovered in 94.4% of subjects. The treatment was safe and well tolerated. Complications encountered included massive pneumothorax, which occurred in one subject, requiring pleural drainage. Other complications were moderate pneumothorax (also requiring pleural drainage), cough, fever, slight dyspnea, and pain, but these complications were short in duration and successfully treated.

CONCLUSION

Radiofrequency thermal ablation is a promising technique in the treatment of patients with lung neoplasms and has been found to be both safe and technically feasible.

Histopathologic evaluation of tissue extracted on the radiofrequency probe after ablation of liver tumors: preliminary findings

OBJECTIVE

Our aim was to evaluate the histologic characteristics of tissue extracted on the probe immediately after radiofrequency ablation of malignant tumors in the liver.

MATERIALS AND METHODS

From April to December 2001, 20 radiofrequency ablations were performed in 19 patients with primary (n = 17) and metastatic (n = 2) liver masses. Track ablation according to device protocol was performed after each ablation. Tissue was adherent to the probe after all radiofrequency probe passes. All pieces of tissue found on the probe were collected and preserved in formalin.

RESULTS

Tissue was examined by the study pathologist. In eight (40%) of 20 specimens, coagulation necrosis was present. In five (25%) of 20 specimens, possibly nonviable tissue was extracted, although some cell characteristics were identified. In seven (35%) of 20 specimens with hepatocellular carcinoma, possibly viable tissue was found. Five specimens were identified as hepatocellular carcinoma, and two, as cirrhotic nodules.

CONCLUSION

Histopathologic evaluation of the tissue extracted on the radiofrequency probe after ablation is feasible. This study showed that coagulation necrosis was clearly present in at least 40% of the patients, which proves that nonviable tissue can be seen immediately after ablation. Whether this pathologic finding has prognostic value is not known.

Intraoperative radiofrequency ablation (RFA) for irresectable liver malignancies

AIMS

To evaluate the outcome of patients who received radiofrequency ablation (RFA) at open laparotomy in patients with irresectable liver malignancies.

METHODS

Twenty-six consecutive patients who underwent explorative laparotomy and were found to be irresectable or who had been assessed not suitable for either resection or percutaneous RFA received intraoperative RFA. An expandable electrode (RITA Medical systems) was used. Follow-up comprised CT-scans in 6-12 week intervals.

RESULTS

Patients' age ranged from 35 to 72 years (median 61). A variety of pathologies were treated. In 26 patients, 88 hepatic lesions were treated: 32 with resection and 56 with RFA. The mean diameter was 4.0+/-2.6 cm with a maximum of 10 cm. In 22 patients with hepatic metastases (18 colorectal, one leiomyosarcoma, one endometrium carcinoma, one renal cell carcinoma, one malignant phaeochromocytoma) 74 lesions (median 3.4 per patient) were treated (25 by resection, 49 by RFA). Eleven patients received simultaneous resection and RFA: resection of anatomical segments in six and atypical resection in seven patients. Procedure related complication rate was 19.2%. The mean follow-up was 14.6+/-9.2 months (2-36 months). Three patients developed recurrence at the site of previous RFA indicating incomplete ablation. The overall local control rate after one year was 92 and 90.9% for patients with colorectal liver metastases, respectively. Seventeen patients (65.4%) suffered from tumour progress. In 14 patients (53.9%) tumour occurred at new hepatic localisations and in five patients extrahepatic tumour relapse was diagnosed. Twelve patients have died so far (median survival 18 months, range 4-27). Nineteen patients had either completed a follow-up of at least 12 months or died within this period, resulting in an one year survival rate of 79% (80% for liver metastases).

CONCLUSION

Intraoperative RFA is a valuable tool in liver surgery which extends the surgical spectrum in cases of irresectable malignancies.

Delayed portal vein thrombosis after experimental radiofrequency ablation near the main portal vein

BACKGROUND

Portal venous blood flow may protect adjacent tumour cells from thermal destruction with radiofrequency ablation (RFA). This study aimed to investigate the local effect of RFA on the main portal vein branch, and the completeness of cellular ablation in its vicinity, with or without a Pringle manoeuvre using a porcine model.

METHODS

This was an in vivo study on 23 domestic pigs. RFA using a cooled-tip electrode was performed 5 mm from the left main portal vein branch under ultrasonographic guidance for 12 min with (n = 10) or without (n = 10) a Pringle manoeuvre. Ten pigs were killed 4 h after the procedure to study the early effects of RFA and ten others were killed 1 week later to determine any delayed effect. As a control, sham operations with a Pringle manoeuvre for 12 min were performed on three pigs. The flow velocity changes of portal vein and hepatic artery were measured using Doppler ultrasonography, and the completeness of cellular ablation around the portal vein was assessed qualitatively by histochemical staining and quantitatively by measuring intracellular levels of adenosine 5'-triphosphate (ATP).

RESULTS

In the absence of the Pringle manoeuvre, there was no significant change in mean(s.d.) portal vein flow velocity before RFA (20.0(3.5) cm/s) and at 4 h (18.5(2.5) cm/s) (P = 0.210) and 1 week (19.5(2.2) cm/s) (P = 0.500) after the procedure. Gross and histological examination of the portal vein branches showed no damage without the Pringle manoeuvre. In all pigs that underwent RFA with a Pringle manoeuvre, the portal vein was occluded 1 week after the operation; histological examination of the affected portal vein showed severe thermal injury and associated venous thrombosis. The local effect of RFA on the hepatic artery was similar. With intact portal blood flow during RFA, complete ablation of liver tissue around the pedicle was demonstrated by histochemical staining and measurement of the intracellular ATP concentration.

CONCLUSION

RFA was safe when applied close to the main portal vein branch without a Pringle manoeuvre, with complete cellular destruction. Use of the Pringle manoeuvre resulted in delayed portal vein and hepatic artery thrombosis and injury to the hepatic artery and bile duct.

Saline-linked surface radiofrequency ablation: factors affecting steam popping and depth of injury in the pig liver

SUMMARY BACKGROUND DATA

Saline-linked surface radiofrequency (RF) ablation is a new technique for applying RF energy to surfaces. The surface is cooled, which prevents charring and results in deeper coagulation. However, subsurface heating may lead to steam formation and a form of tissue disruption called steam popping. We determined parameters that predict steam popping and depth of tissue destruction under nonpopping conditions. A commercially available saline-linked surface RF cautery device (Floating Ball 3.0, TissueLink, Inc.) was used.

METHODS

One hundred eighty circular lesions were created varying in lesion diameter, duration, power, and inflow occlusion. Variables affecting popping were determined. Then factors influencing lesion depth were studied at fixed nonpopping diameter/power combinations (1 cm/10W, 2 cm/15W, 4 cm/60W). Tissue viability was determined in selected samples by staining of tissue NADH.

RESULTS

The probability of steam popping was directly related to power level and inflow occlusion, and indirectly related to lesion diameter. Depth of injury under safe nonpopping conditions was directly related to power, lesion size, and inflow occlusion. Maximum depth in excess of 20 mm was achieved using a 4 cm diameter at 60W with inflow occlusion. Microscopy of NADH-stained tissues showed a complete cell killing in the macroscopically visible coagulated area.

CONCLUSIONS

Steam popping can be avoided by selecting power level/lesion diameter combinations. Tissue destruction to 20 mm can be safely achieved with short periods of inflow occlusion. The device has promise as a treatment of superficial tumors and close resection margins.

Comparison of transcatheter arterial chemoembolization, laparoscopic radiofrequency ablation, and conservative treatment for decompensated cirrhotic patients with hepatocellular carcinoma

AIM: To compare the therapeutic effect of transcatheter arterial chemoembolization (TACE), laparoscopic radiofrequency ablation (LRFA), and conservative treatment for the therapy of decompensated liver cirrhosis patients with hepatocellular carcinomas (HCC).

METHODS: Between October 2000 and July 2003, one hundred patients with histologically proven primary HCC and clinical decompensated liver cirrhosis (Child classification B or C) were included in this study. Forty patients received LRFA (LRFA group), twenty received TACE (TACE group), and forty received conservative treatment (control group). We compared the survival, recurrence, and complication rates in these three groups, making adjustment using the tumor metastastic node staging system.

RESULTS: The major complication rate in the TACE group (9/20) was significantly higher than that in the LRFA group (7/40). For patients with TMN stage II HCC, the survival rate of the LRFA group was better than that of the TACE and control groups (P = 0.003) but the recurrence rates befween the LRFA and TACE groups did not differ.

CONCLUSION: The LRFA group of patients had better clinical outcomes in terms of survival and complication rates in comparison with the TACE group or conservative treatment in patients with decompensated liver cirrhosis, especially in TMN patients with stage II HCC. LRFA is thus an appropriate alternative treatment for poor liver function among patients with HCC.

Percutaneous ablation of liver tumours

The goal of local ablation treatment of hepatic disease is to prolong survival for patients with unresectable tumours. Presently, influence on survival is difficult to estimate because of the heterogeneity of indications and treatments and short follow-up. This chapter therefore focuses on potential benefits and limitations, complications and solutions for improvement. The main problems with in situ ablation are the lack of good imaging techniques to determine the extent of disease and the lack of a method for real-time monitoring of irreversible tissue effect. With one exception, there are no prospective, randomized studies comparing local destruction methods. It appears that percutaneous ethanol injection and cryotherapy should be replaced by radiofrequency ablation (RFA) or interstitial laser thermotherapy (ILT) and that there is little difference in outcome between RFA and ILT. Intraoperative RFA or ILT is valuable as an adjunct to hepatic resection in order to increase the rate of resectability. The percutaneous approach needs further development. It might be valuable in a few truly unresectable or inoperable patients or in selected patients with neuroendocrine liver metastases. In the large majority of unresectable patients it should, however, presently be used and evaluated only in prospective, randomized studies.

Comparison of resection and radiofrequency ablation for treatment of solitary colorectal liver metastases

BACKGROUND

Liver resection is the treatment of choice for patients with solitary colorectal liver metastases. In recent years, however, radiofrequency ablation has been used increasingly in the treatment of colorectal liver metastases. In the absence of randomized clinical trials, this study aimed to compare outcome in patients with solitary colorectal liver metastases treated by surgery or by radiofrequency ablation.

METHODS

Solitary colorectal liver metastases were treated by radiofrequency destruction in 25 patients. The indications were extrahepatic disease in seven, vessel contiguity in nine and co-morbidity in nine patients. Outcome was compared with that of 20 patients who were treated by liver resection for solitary metastases and had no evidence of extrahepatic disease. Most patients in both groups also received systemic chemotherapy.

RESULTS

Median survival after liver resection was 41 (range 0-97) months with a 3-year survival rate of 55.4 per cent. There was one postoperative death and morbidity was minimal. Median survival after radiofrequency ablation was 37 (range 9-67) months with a 3-year survival rate of 52.6 per cent.

CONCLUSION

Survival after resection and radiofrequency ablation of solitary colorectal liver metastases was comparable. The latter is less invasive and requires either an overnight stay or day-case facilities only.

Bipolar saline-enhanced electrode for radiofrequency ablation: results of experimental study of in vivo porcine liver

PURPOSE

To evaluate whether a bipolar saline-enhanced radiofrequency (RF) ablation system embedded in one needle is able to consistently produce homogeneous and predictable areas of coagulation necrosis with or without the Pringle maneuver of vascular inflow occlusion.

MATERIALS AND METHODS

RF ablation (480 kHz) of the liver was performed in 24 healthy pigs by means of laparotomy: group A (n = 5), 4-cm distance between electrodes 1 and 2; group B (n = 7), 4-cm distance and the Pringle maneuver; group C (n = 5), 2-cm distance; and group D (n = 7), 2-cm distance with the Pringle maneuver. Twenty percent NaCl solution was infused continuously at a rate of 100 mL/h via each electrode during the procedure. The pigs were followed up, and they were euthanized on the 7th day. Livers were removed for histologic assessment. Time, impedance, current, power output, specific voltage of the contacts, energy output, temperatures in the liver, volume of the lesion, and energy delivered per lesion volume were determined and compared among groups. Predictability of lesion volume was evaluated with the coefficient of variability. Mean values of the variables were compared among the groups by means of one-way analysis of variance or Kruskall-Wallis test.

RESULTS

Impedance at the end of the RF ablation procedure was almost twofold lower than the corresponding initial value in all groups. In Pringle groups B and D, regular ellipsoids of coagulation necrosis were created (mean lesion volume, 149.50 cm3 +/- 34.26 and 69.43 cm3 +/- 15.48, respectively). In non-Pringle groups A and C, the shape of coagulation necrosis was influenced by the vessels encountered, and mean lesion size was lower than that in the Pringle groups (P <.01). The coefficient of variability of lesion size was lower in the Pringle groups (23% and 22%, respectively) than that in the non-Pringle groups (75% and 30%, respectively).

CONCLUSION

The bipolar saline-enhanced RF ablation method produces homogeneous and predictable areas of coagulation necrosis between two electrodes, regardless of the distance between them, preferably with vascular inflow occlusion.

Histopathological changes after microwave coagulation therapy for patients with hepatocellular carcinoma: review of 15 explanted livers

OBJECTIVES

Microwave coagulation therapy (MCT) is a well established local ablation technique for hepatocellular carcinoma (HCC). However, pathological changes in liver tissue after this therapy have not been well described. We examined the histological changes of HCC after MCT observed in explanted livers in relation to CT findings.

METHODS

A total of 15 patients with 18 lesions of HCC underwent MCT and subsequent liver transplantation. Explanted livers were examined macro- and microscopically, and an evaluation of mitochondrial activity of ablated tissue was accomplished by using succinic dehydrogenase (SDH) stain in frozen sections.

RESULTS

Of the 18 lesions, 16 were ablated completely and another two had residual tumor. The size of the ablated areas on CT scan corresponded to the macroscopic findings. Histologically the area of ablation was rimmed by a palisading, histiocytic, giant cell, inflammatory reaction associated with fibrotic bands. Coagulative necrosis with faded nuclei and eosinophilic cytoplasm were the predominant findings in the ablated areas. There were also areas in which the tumor cells had cytoplasmic eosinophilia, but nuclei were present and the cells seemed to be viable. On the SDH stain of frozen tissue taken from the edge of the ablated area, SDH activity was negative in both necrotic and nonnecrotic ablated areas.

CONCLUSIONS

Most of the treated areas after microwave ablation develop coagulative necrosis accompanied by a foreign body-like inflammatory reaction and fibrosis. Pathologists need to be aware that after this form of therapy, portions of the tumor maintain their native morphological features as if the area is fixed, but their cellular activity is destroyed.

Thermal ablative therapy for malignant liver tumors: a critical appraisal

The management of primary and secondary malignant liver tumors poses a great challenge to clinicians. Although surgical resection is the gold-standard treatment, most patients have unresectable malignant liver tumors. Over the past decade, various modalities of loco-regional therapy have gained much interest. Among them, thermal ablative therapy, including cryotherapy, microwave coagulation, interstitial laser therapy, and radiofrequency ablation (RFA), have been proven to be safe and effective. Despite the effective tumor eradication achieved within cryotherapy, the underlying freeze/thaw mechanism has resulted in serious complications that include bleeding from liver cracking and the 'cryoshock' phenomenon. Thermal ablation using microwave and laser therapy for malignant liver tumors is curative and is associated with minimal complications. However, this treatment modality is effective only for tumors <3 cm diameter. Radiofrequency ablation seems to be the most promising form of thermal ablative therapy in terms of a lower complication rate and a larger volume of ablation. However, its use is restricted by the difficulty encountered when using imaging studies to monitor the areas of ablation during and after the procedure. Moreover, the techniques of RFA need to be refined in order to achieve the same oncological radicality of malignant liver tumors as achieved by surgical resection. As each of the loco-regional therapies has its own advantages and limitations, a multidisciplinary approach using a combination of therapies will be the future trend for the management of malignant liver tumors.

Radiofrequency ablation extends the scope of surgery in colorectal liver metastases

AIMS

To assess outcome in patients treated by a multidisciplinary team, with a combination of liver resection and RF ablation.

METHODS

Sixteen unselected patients (f=9; m=7) with colorectal liver metastases who were not suitable for surgery alone, were treated as follows: six had RF ablation at open laparotomy, three patients had synchronous ablation and resection while seven patients had RF ablation after liver resection. Standard liver resection techniques were used. RF was performed using internally cooled, single or cluster electrodes with a high power (200 W) generator. All patients were followed with regular contrast enhanced CT and survival noted.

RESULTS

A total of 27 tumours with diameters 1.2-10 cm were treated. Two minor complications were recorded. 2/6 (33%) who had intraoperative RF had incomplete ablation due to large tumour size (6 and 10 cm respectively). Further RF ablation sessions were carried out successfully. 11/16 (69%) are alive at 2 years of whom 7 (44%) have no evidence of residual or recurrent liver disease.

CONCLUSION

In our study, RF ablation extends the therapeutic envelope, is an effective local treatment of liver metastases and improves life expectancy.

Interstitial ablative techniques for hepatic tumours

BACKGROUND

Most patients with liver tumours are not suitable for surgery but interstitial ablative techniques may control disease progression and improve survival rates.

METHODS

A review was undertaken using Medline of all reported studies of cryoablation, radiofrequency ablation, microwave ablation, interstitial laser photocoagulation, high-intensity focused ultrasound and ethanol ablation of primary liver tumours and hepatic metastases.

RESULTS

Although there are no randomized clinical trials, cryoablation, thermal ablation and ethanol ablation have all been shown to be associated with improved palliation in patients with primary and secondary liver cancer. The techniques can be undertaken safely with minimal morbidity and mortality.

CONCLUSION

Although surgical resection remains the first line of treatment for selected patients with primary and secondary liver malignancies, interstitial ablative techniques are promising therapies for patients not suitable for hepatic resection or as an adjunct to liver surgery.

Large hepatic ablation with bipolar saline-enhanced radiofrequency: an experimental study in in vivo porcine liver with a novel approach

SUMMARY BACKGROUND DATA

Radiofrequency ablation (RFA) is a relatively new technology for the local destruction of liver tumors. Development of recent devices has enabled the creation of larger lesions. Nevertheless, treating liver tumors larger than 2.5 cm in diameter often requires multiple overlapping ablations to encompass the tumor and the surrounding healthy tissue rim with an increasing risk of local recurrence.

MATERIAL AND METHODS

RFA (480 kHz) of the liver using our method was undertaken on a total number of 15 healthy farm pigs with (Group B, n = 8) or without (Group A, n = 5) the Pringle maneuver via laparotomy. The pigs were followed and euthanized on the seventh day of the experiment. Livers were removed for histological assessment. Time of the procedure, impedance, current, power output, energy output, temperatures in the liver, central temperature of the animal, volume size of the lesion, and delivered energy per lesion volume were determined and compared among groups. Additionally a regularity ratio (RR) was determined by gross examination of the specimen and scored (0-3) taking into account regularity and predictability of the ablation with pathologic assessment.

RESULTS

With both methods, ellipsoid lesions were created between the two probes. In both groups tissue impedance fell with time (r = -0.47, P < 0.01 and r = -0.34, P < 0.05, in Groups A and B, respectively). The mean lesion size achieved with the Pringle maneuver was the largest lesion size described in the literature for any RFA method in vivo and was greater in Group B than in Group A (123.22 cm(3) +/- 49.62 and 52.40 cm(3) +/- 23.59, respectively, P < 0.05). A better regularity and predictability evaluated by RR was observed in Group B compared to Group A (1.88 +/- 1.35 and 0.40 +/- 0.55, respectively, P < 0.05). Five major complications were described and attributed primarily to failure in isolation from hypertermic lesions.

CONCLUSIONS

Our new bipolar saline-enhanced electrode with Pringle maneuver achieves large hepatic ablations in in vivo pig liver. These large lesions are well-tolerated by the animal when thermal injuries to adjacent structures are avoided.

Portal vein thrombosis after radiofrequency ablation for recurrent hepatocellular carcinoma

Recurrent hepatocellular carcinoma (HCC) deserves multidisciplinary treatment in addition to surgical resection. Radiofrequency ablation (RFA) is an evolving, localized, thermal ablative treatment for unresectable hepatocellular carcinoma (HCC). Though the preliminary results of RFA in clinical studies are encouraging, its serious complications should not be underestimated. Portal vein thrombosis as a result of direct blood vessel injury by RFA is rarely reported and is potentially fatal in patients with limited liver reserve due to underlying liver cirrhosis. We present a case of portal vein thrombosis as a complication of RFA treatment for recurrent HCC and illustrate its underlying possible mechanism.

Complications of radiofrequency coagulation of liver tumours

BACKGROUND

Radiofrequency coagulation (RFC) is being promoted as a novel technique with a low morbidity rate in the treatment of liver tumours. The purpose of this study was to assess critically the complication rates of RFC in centres with both large and limited initial experience, and to establish causes and possible means of prevention and treatment.

METHODS

This is an exhaustive review of the world literature (articles and abstracts) up to 31 December 2001; 82 independent reports of RFC of liver tumours were analysed.

RESULTS

In total, 3670 patients were treated with percutaneous, laparoscopic or open RFC. The mortality rate was 0.5 per cent. Complications occurred in 8.9 per cent: abdominal bleeding in 1.6 per cent, abdominal infection in 1.1 per cent, biliary tract damage in 1.0 per cent, liver failure in 0.8 per cent, pulmonary complications in 0.8 per cent, dispersive pad skin burn in 0.6 per cent, hepatic vascular damage in 0.6 per cent, visceral damage in 0.5 per cent, cardiac complications in 0.4 per cent, myoglobinaemia or myoglobinuria in 0.2 per cent, renal failure in 0.1 per cent, tumour seeding in 0.2 per cent, coagulopathy in 0.2 per cent, and hormonal complications in 0.1 per cent. The complication rate was 7.2, 9.5, 9.9 and 31.8 per cent after a percutaneous, laparoscopic, simple open and combined open approach respectively. The mortality rate was 0.5, 0, 0 and 4.5 per cent respectively.

CONCLUSION

The morbidity and mortality of RFC, while low, is higher than previously assumed. With adequate knowledge, many complications are preventable.

Hyperkalaemia after radiofrequency ablation of hepatocellular carcinoma

Radiofrequency ablation of liver tumours is a useful therapy for otherwise unresectable tumours. The complication rate is said to be low. In this case report we describe hyperkalaemia after radiofrequency ablation of a hepatocellular carcinoma in a patient with end-stage renal insufficiency.

The effect of hepatic inflow occlusion on laparoscopic radiofrequency ablation using simulated tumors

BACKGROUND

The purpose of this study was to determine the effect of hepatic inflow occlusion (the Pringle maneuver) on laparoscopic radiofrequency (RF) ablation.

METHODS

Using a previously validated agarose tissue-mimic model, 1-cm simulated hepatic tumors (three per animal) were laparoscopically ablated in five pigs with normal perfusion and then in five pigs with hepatic artery and portal vein occlusion. Energy was applied until tissue temperature reached 100 degrees C (warm-up) and thereafter for eight min. Specimens were examined immediately after treatment.

RESULTS

Vascular occlusion was successful in all cases per color-flow Doppler ultrasound. Pringle time was 11.4 +/- 1.6 min. Warm-up time (2.7 +/- 1.4 vs 20.2 +/- 14.0 min) was significantly faster in the Pringle group. Ablation diameter (34.8 +/- 2.9 vs 24.7 +/- 3.1 mm), proportion of round/ovoid lesions (93% vs 20%), ablation symmetry (100% vs 40%), and margin distance (5.1 +/- 3.0 vs 1.1 +/- 1.2 mm) were significantly better for the Pringle group than the No Pringle group, respectively.

CONCLUSION

Using a Pringle maneuver during laparoscopic RF ablation significantly enhances ablation geometry and results in larger margins.

Clinical short-term results of radiofrequency ablation in liver cancers

AIM: To study local therapeutic efficacy, side effects, and complications of radiofrequency ablation (RFA), which is emerging as a new method for the treatment of patients with hepatocellular carcinoma (HCC) with cirrhosis or chronic hepatitis and metastatic liver cancer.

METHODS: Thirty-six patients with primary and secondary liver cancers (21 with primary hepatocellular carcinoma, 12 with colorectal cancer liver metastases and 3 with other malignant liver metastases), which were considered not suitable for curative resection, were include in this study. They were treated either with RFA (RITA2000, Mountain View, California, USA) percutaneously (n = 20) or intraoperatively (n = 16). The procedures were performed using the ultrasound guidance. The quality of RFA were based on monitoring of equipments and subject feeling of the practitioners. Patients treated with RFA was followed according to clinical findings, radiographic images, and tumor markers.

RESULTS: Thirty-six patients underwent RFA for 48 nodules. RFA was used to treat an average 1.3 lesions per patient, and the median size of treated lesions was 2.5 cm (range, 0.5-9 cm). The average hospital stay was 5.6 d overall (2.8 d for percutaneous cases and 7.9 d for open operations). Seven patients underwent a second RFA procedure (sequential ablations). Sixteen HCC patients with a high level of alpha fetoprotein (AFP) and 9 colorectal cancer liver metastases patients with a high level of serum carcinoembryonic antigen (CEA) have a great reduction benefited from RFA. Four (11.1%) patients had complications: one skin burn; one postoperative hemorrhage; one cholecystitis and one hepatic abscess associated with percutaneous ablations of a large lesion. There were 4 deaths: 3 patients died from local and system diseases (1 at 7 month, 1 at 9 month, and 1 at 12 month), 1 patients died from cardiovascular shock, but no RFA-related death. At a median follow-up of 10 mo (range, 1-24 mo), 6 patients (16.7%) had recurrences at an RFA site, and 20 patients (56.7%) remained clinically free of disease.

CONCLUSION: RF ablation appears to be an effective, safe, and relatively simple procedure for the treatment of unresectable liver cancers. The rate and severity of complications appear acceptable. However, further study is necessary to assess combination with other therapies, long-term recurrence rates and effect on overall survival.

Radiofrequency ablation of the porcine liver with complete hepatic vascular occlusion

BACKGROUND

We studied the effects of radiofrequency ablation, relative to hepatic blood flow, on the volume and shape of the resulting tissue necrosis. The extent of necrosis is directly proportional to the size of the electrode and inversely related to blood flow, which dissipates the heat generated.

METHODS

Two areas of necrosis were created in each of eight porcine livers, which were assigned to four groups according to blood flow occlusion: no occlusion, occlusion of the hepatic artery and portal vein, occlusion of the hepatic veins, and complete hepatic vascular occlusion. After 25 minutes of liver reperfusion, the animals were euthanized, and the livers were examined.

RESULTS

Complete vascular occlusion resulted in the greatest area of necrosis (28.6 +/- 3.4 cm(3)), followed by occlusion of the hepatic artery and portal vein (19.2 +/- 5.9 cm(3)), occlusion of hepatic veins (14.4 +/- 2.6 cm(3)), and no occlusion (4.9 +/- 1.5 cm(3)). The volume of the necrotic areas created during complete vascular occlusion were significantly greater than those created with no occlusion, as well as those created with only the hepatic artery and portal vein occluded (P <.05).

CONCLUSIONS

Complete vascular occlusion, combined with radiofrequency ablation, increases the volume of necrosis and creates a more spherical ablative area.

Treatment of hepatocellular carcinoma with radiofrequency ablation: radiologic-histologic correlation during follow-up periods

To determine whether radiographic images after radiofrequency (RF)-induced coagulation necrosis are correlated with the pathologic effects, we evaluated the morphology and histologic characteristics of RF ablation lesions over a 6-month follow-up period and compared the results with those of radiologic studies. Thirty-three hepatocellular carcinoma (HCC) tumors with a maximum diameter of 3 cm or less were treated percutaneously by using RF ablation in 26 patients. Six treated tumors were resected 4 weeks after ablation; the remaining 27 treated tumors underwent a biopsy procedure by using an 18-gauge fine needle 3 days, 4 weeks, and 24 weeks after ablation. The excised or biopsied lesions were examined by using histologic methods; the findings were then compared with those of contrast-enhanced computed tomography (CT). Three days after ablation, a core of hypoattenuation surrounded by an enhanced/hemorrhagic rim was observed on the contrast-enhanced CT images. Hematoxylin-eosin-stained specimens were inconclusive as to whether or not cellular viability remained; however, cell viability as determined by the presence of histochemical (lactate-dehydrogenase, maleate-dehydrogenase, and the reduced form of nicotinamide-adenine dinucleotide phosphate [NADPH]-diaphorase) stains was absent, suggesting 100% cellular destruction in the ablated lesion. Four and 24 weeks after ablation, the sizes of the ablated lesions were progressively smaller on the CT images; the histochemical stains remained superior to the hematoxylin-eosin stains for obtaining a definite diagnosis of cell death. We conclude that irreversible cellular destruction, as determined by the absence of positive histochemical staining patterns, was useful for evaluating the pathologic thermal effect of RF ablation. These pathologic findings can be correlated with those of contrast-enhanced CT.

Hand-assisted laparoscopic ultrasound-guided radiofrequency thermal ablation of liver tumors: a technical report

Ultrasound-guided radiofrequency thermal ablation has been performed for liver tumors by percutaneous, laparoscopic, or open surgical approaches. Each approach has specific advantages and disadvantages. Herein we describe a new technique for hand-assisted laparoscopic ultrasound-guided radiofrequency thermal ablation of liver tumors. A hand-access device is placed at the right or central portion of the abdomen, in addition to standard trocars. A conventional intraoperative ultrasound probe, with an ultrasound guidance system attached, is inserted into the peritoneal cavity together with the surgeon's hand. After pneumoperitoneum is established, an electrode-cannula for thermal ablation is introduced subcostally or intercostally, and advanced into a liver tumor under direct guidance by intraoperative ultrasound. We have used this technique in eight patients with unresectable liver tumors. Precise guidance of the cannula into tumors was possible. All tumors were well ablated. The postoperative recovery of patients was of shorter duration compared with that of an open surgical approach. A hand-assisted laparoscopic ultrasound-guided method has advantages of both laparoscopic and open surgical approaches for radiofrequency thermal ablation treatment of liver tumors. Accurate cannula insertion is possible with the ultrasound guidance system. The hand-assisted laparoscopic approach can become an additional useful technique, particularly as a valuable alternative to an open surgical method, for performing radiofrequency thermal ablation.

Sonographically observed echogenic response during intraoperative radiofrequency ablation of cirrhotic livers: pathologic correlation

OBJECTIVE

We performed a study to determine the correlation between the diameter of the echogenic response observed with intraoperative sonography during radiofrequency ablation of the cirrhotic liver and the mean diameter of tissue necrosis.

SUBJECTS AND METHODS

A total of 22 intraoperative radiofrequency ablations were created in 11 cirrhotic livers. The largest diameter of the sonographically observed echogenic response surrounding and perpendicular to the radiofrequency probe was measured. The subsequent zone of necrosis observed at pathology in the hepatectomy specimens after liver transplantation was measured in three planes and compared with the measured diameter of the echogenic response.

RESULTS

During all except three ablations, a hyperechoic region was visualized surrounding the radiofrequency probe. The diameter of the echogenic response correlated significantly with the mean diameter of necrosis (correlation coefficient, 0.84). However, the echogenic response overestimated the minimal diameter of necrosis (mean difference, 0.8 +/- 0.4 cm) in 18 of 22 ablations and underestimated the maximum diameter of necrosis (mean difference, 0.9 +/- 0.8 cm) in 16 of 22 ablations.

CONCLUSION

The diameter of the echogenic response observed with intraoperative sonography during radiofrequency ablation of the cirrhotic liver correlates closely with the mean diameter of the subsequent area of tissue necrosis. However, the solitary diameter of the echogenic response as measured in our study was often greater than the smallest diameter and less than the largest diameter of the area of tissue necrosis. Therefore, the echogenic response associated with radiofrequency ablation of the cirrhotic liver should be viewed only as a rough approximation of the area of induced tissue necrosis; the final assessment of the adequacy of ablation should be deferred to an alternative imaging technique.

Immunohistochemical detection of hepatocellular carcinoma in the setting of ongoing necrosis after radiofrequency ablation

After radiofrequency ablation (RFA), hepatocellular carcinoma undergoes complete necrosis and an ongoing necrosis that is irreversible and characterized histologically by disrupted cell outlines, homogenous cytoplasmic eosinophilia, and preserved nuclear staining, with the cells appearing quite distinct from viable cancer cells. Antibody to detect single-stranded DNA (ssDNA) specifically labeled nuclei in the setting of ongoing necrosis, but not viable tumor cells, whereas human mitochondrial antibody labeled the cytoplasm of viable cells but not cells of ongoing necrosis. The results demonstrate that RFA causes denaturation of both DNA and proteins and that the immunohistochemistry of ssDNA and mitochondrial protein is useful in detection of ongoing necrosis after RFA and provides pathological information on the validity of this procedure.

Radiofrequency ablation for unresectable hepatic tumors

BACKGROUND

Radiofrequency ablation (RFA) is a relatively new treatment for unresectable hepatic tumors. The purpose of this analysis was to examine the frequency of complications and local recurrence associated with RFA.

METHODS

Patients who underwent RFA of hepatic tumors with curative intent were included in this study. At laparotomy, RFA was performed using intraoperative ultrasound guidance. Computed tomography scans were obtained in the immediate postoperative period and every 3 to 6 months thereafter.

RESULTS

Forty patients underwent RFA for 122 hepatic tumors. Thirty-one patients had metastatic lesions from colorectal cancer; 9 had other liver tumors. Complications occurred in 8 patients. With 9.5 months median follow-up, 6 patients had local recurrence of their ablated tumors.

CONCLUSIONS

Our initial experience shows that RFA can effectively eradicate unresectable hepatic tumors. The rate and severity of complications appear acceptable. However, further study is necessary to assess long-term recurrence rates and effect on overall survival.

Ultrasound-guided radiofrequency thermal ablation of liver tumors: percutaneous, laparoscopic, and open surgical approaches

Only 10% to 20% of patients with primary and colorectal metastatic liver tumors are candidates for curative surgical resection. Even after curative treatment, tumors recur commonly in the liver. As a less invasive therapy, radiofrequency thermal ablation (RFA) of primary, metastatic, and recurrent liver tumors was performed under percutaneous, laparoscopic, or open intraoperative ultrasound guidance. The safety and local control efficacy of RFA were investigated. RFA was performed mostly in patients with unresectable hepatomas or metastatic liver tumors. Patients with large tumors, major vessel or bile duct invasion, limited extrahepatic metastases, or liver dysfunction were not excluded. An RFA system with a 15-gauge electrode-cannula with four-pronged retractable needles was used. All patients were followed for more than 8 months to assess morbidity and mortality, and to determine tumor recurrence. Sixty RFA operations were performed in 46 patients: 11 patients underwent repeat RFA once or twice. A total of 204 tumors were treated: 70 hepatomas and 134 metastatic tumors. Tumor size ranged from 5 mm to 180 mm (mean 36 mm). RFA was performed in 29 operations for 81 tumors percutaneously, in seven operations for 14 tumors laparoscopically, and in 24 operations for 109 tumors by open surgery. Combined colorectal resection was carried out in five operations and combined hepatic resection was carried out in three operations. There was one death (1.7%) from liver failure, and there were three major complications (5%): one case of bile leakage and two biliary strictures due to thermal injury. There were no intra-abdominal infectious or bleeding complications. The length of hospital stay ranged from 0 to 2, 1 to 3, and 4 to 7 days for percutaneous, laparoscopic, and open surgical RFA, respectively. During a mean follow-up period of 20.5 months, local tumor recurrence at the RFA site was diagnosed in 18 (8.8%) of 204 tumors. The risk factors for local recurrence included large tumor size and major vessel invasion: recurrence rates for tumors less than 4 cm, 4 to 10 cm, and greater than 10 cm, and for those with vessel invasion were 3.3%, 14.7%, 50%, and 47.8%, respectively. Ten of 18 tumors recurring locally were retreated by RFA, and eight of them showed no further recurrence. Ultrasound-guided RFA is a relatively safe, well-tolerated, and versatile treatment option that offers excellent local control of primary and metastatic liver tumors. The appropriate use of percutaneous, laparoscopic, and open surgical RFA is beneficial in the management of patients with liver tumors in a variety of situations.

Radiofrequency ablation of unresectable hepatic malignancies: lessons learned

Radiofrequency ablation (RFA) is increasingly used for the local destruction of unresectable hepatic malignancies. Relative contraindications include tumors in proximity to vital structures that may be injured by RFA and lesions whose size exceeds the ablation capabilities of the probe system employed. Given current technology, we believe that RFA should be cautiously utilized for lesions greater than 5 cm in diameter. Open (celiotomy) and laparoscopic approaches to RFA allow intraoperative ultrasonography, which may demonstrate occult hepatic disease. In addition, RFA performed via celiotomy can be accompanied by resection or cryosurgical ablation, and isolation of the liver from adjacent organs. Percutaneous RFA should be reserved for patients who cannot undergo general anesthesia, those with recurrent or progressive lesions, and those with smaller lesions sufficiently isolated from adjacent organs. Complications may be minimized when these approaches are selectively applied.

[Radiofrequency ablation of malignant hepatic tumors. Preliminary experience apropos of 25 cases]

STUDY AIM

Radiofrequency (RF) ablation of malignant hepatic tumors is an interesting and recent technique which offers new treatment possibilities. In this study, the preliminary findings have been reported on 25 patients with hepatic tumors who received RF treatment between January 1998 and February 2000.

PATIENTS AND METHODS

Twenty-five patients (11 cases of hepatocellular carcinoma, HCC; and 14 cases of liver metastases, LM) underwent RF treatment. Thirty tumors (range: 10 to 54 mm in diameter) out of a total of 63 were destroyed by RF: 13 HCC (average diameter: 32 mm) and 17 LM (average diameter: 26 mm). Treatment consisted of six percutaneous and 19 surgical RF procedures. In the surgical group, there were 11 cases of hepatectomy: right hepatectomy in five patients with segment IV enlargement in one case, and sub-segmentectomy in six other patients. In all cases, hepatic tomodensitometry was performed at one month post-treatment and then every three months.

RESULTS

Postoperative portal thrombosis occurred in two patients, one of whom died. Other postoperative complications were observed in five patients. During the mean follow-up period of 14 months (range: 2 to 28 months), two patients died (carcinosis, ascitic decompensation), two and four months respectively after RF treatment. In situ recurrence occurred in four HCC and two LM patients. Three HCC and four LM patients developed new hepatic or extra-hepatic lesions.

CONCLUSION

RF is a particularly interesting technique for the treatment of bilobar or unresectable metastases. It appears to be equally as efficient as other local treatments for small-sized HCC. However, technical improvements remain necessary to increase the destructive field covered by RF. A more important follow-up is needed so that the long-term efficacy and specific role of this new therapy can be accurately assessed.

Accuracy and effectiveness of laparoscopic vs open hepatic radiofrequency ablation

BACKGROUND

The purpose of this study was to compare the accuracy (in terms of ultrasound-guided probe placement) and the effectiveness (in terms of pathologic tumor-free margin) of laparoscopic vs open radiofrequency (RF) ablation.

METHODS

Using a previously validated tissue-mimic model, 1-cm simulated hepatic tumors were ablated in 10 pigs randomized to open or laparoscopic techniques. Energy was applied until tissue temperature reached 100 degrees C (warm-up) and thereafter for 8 min. A pathologist blinded to technique examined all specimens immediately after treatment. Analysis was by Fisher's exact test and the Mann-Whitney U test; p < 0.05 was considered significant.

RESULTS

Off-center distance (3.5 +/- 1.6 vs 4.2 +/- 1.4 mm), size (24.7 +/- 3.1 vs 25.6 +/- 3.8 mm), symmetry (40% vs 73%), margin positivity (33% vs 9%), and margin distance (1.1 +/- 1.2 vs 2.2 +/- 1.6 mm) were not significantly different between laparoscopic (n = 15) and open (n = 11) ablations, respectively. The proportion of round/ovoid lesions (20% vs 64%) was lower (p = 0.043), and warm-up time (20.2 +/- 14.0 vs 10.7 +/- 7.5) was longer (p = 0.049) for the laparoscopic than for the open groups, respectively.

CONCLUSION

Accurate probe placement can be achieved using laparoscopic and open RF ablation techniques. The physiologic effects of laparoscopy may alter ablation shape and warm-up time. Additional studies are needed to establish effective ways of achieving complete tumor destruction.

Radiofrequency liver ablation: experimental comparative study of water-cooled versus expandable systems

OBJECTIVE

We evaluate the uniformity and reproducibility of thermal lesion ablation and quantify the volume of tissue destruction and hemorrhage induced with two different commercially available radiofrequency ablation devices.

MATERIALS AND METHODS

A four-array anchor expandable needle electrode and a triple-cluster cooled-tip needle electrode were used to induce lesions in three explanted calf livers and in vivo in eight swine livers. The sizes of the radiofrequency-induced lesions were macroscopically evaluated by measuring two perpendicular dimensions immediately after the experiment. Bleeding was evaluated by weighing gauze swabs used to dry the hemorrhage caused by electrode insertions.

RESULTS

In explanted liver, the mean diameter of the radiofrequency-induced lesion was 5.3 +/- 0.7 cm for the cooled-tip needle and 3.7 +/- 0.4 cm for the expandable needle (p = 0.042), which correspond to approximate volumes of 65.35 +/- 26.22 cm(3) and 26.67 +/- 9.59 cm(3), respectively (p < 0.002). In vivo, the mean diameter was 3.7 +/- 0.4 cm for the cooled-tip needle and 3 +/- 0.4 cm for the expandable needle (p < 0.0001), which correspond to approximate volumes of 24.18 +/- 7.56 cm(3) and 11.16 +/- 3.65 cm(3), respectively (p < 0.0001). Blood loss attained a median value of 3.5 g for the cooled-tip needle and 2.6 g for the expandable needle; this difference was not statistically significant (p = 0.06).

CONCLUSION

The cooled-tip needle induced significantly larger lesions than the expandable needle, but the lesions produced by the expandable needle are more reproducible, uniform, and spheric. The larger size of the lesions produced by the cooled-tip needle may be attributed to the higher maximum power used by the generator and the higher energy deposition, which is due to the cooling of the needle electrode.

Radiofrequency ablation of 100 hepatic metastases with a mean follow-up of more than 1 year

OBJECTIVE

The objective of our study was to evaluate the efficacy and safety of radiofrequency ablation of hepatic metastases performed either percutaneously for treatment of hepatic metastases in patients deemed ineligible for surgery or intraoperatively during partial hepatectomy to destroy unresectable metastases.

SUBJECTS AND METHODS

Sixty-eight patients with 121 hepatic metastases (<5 metastases per patient) that were mainly colorectal in origin underwent 76 sessions of radiofrequency ablation with cooled-needle electrodes under sonographic guidance. Twenty-one patients with 33 metastases of 5-20 mm in diameter (mean +/- SD,13 +/- 7 mm) underwent intraoperative radiofrequency ablation. Forty-seven patients with 88 metastases of 10 to 42 mm in diameter (mean +/- SD, 26 +/- 9 mm) were treated with percutaneous radiofrequency ablation. Procedure efficacy was evaluated with dynamic enhanced CT and MR imaging performed 2, 4, and 6 months after treatment and then every 3 months.

RESULTS

Radiofrequency ablation allowed eradication of 91% of the 100 treated metastases that were followed up for 4-23 months (mean, 13.7 months). Tumor control was equivalent for percutaneous radiofrequency ablation (90%) and for intraoperative radiofrequency ablation (94%). Failure to achieve tumor control occurred mostly with the largest tumor nodules. One bilioperitoneum and two abscesses were the major complications encountered after treatment of 121 metastases with a follow-up of more than 2 months.

CONCLUSION

Radiofrequency ablation appears to be a promising therapeutic modality capable of extending the possibilities of partial hepatectomy and of efficiently treating small metastases percutaneously.

Development of an in vivo tumor-mimic model for learning radiofrequency ablation

Radiofrequency ablation requires accurate probe placement using ultrasound guidance. The purpose of this study was to develop an in vivo tumor-mimic model for learning open and laparoscopic radiofrequency ablation. Tumor-mimics were created in ex vivo porcine livers by injecting a mixture of 3% agarose, 3% cellulose, 7% glycerol, and 0.05% methylene blue, which formed 1 cm hyperechoic, discrete lesions on ultrasound. Open and laparoscopic (using a box-trainer) ablation techniques were practiced. In vivo experiments were then conducted in 10 pigs. Three tumor-mimics were created in each animal using a laparoscopic approach. Lesions were characterized sonographically, ablated using an open (n = 5) or laparoscopic (n = 5) approach, and examined pathologically. An ablation in normal liver tissue was performed as a control. Tissue impedance was recorded. Target creation took 81 minutes per animal and 96% of injections were successful. Tissue impedance (48.8 +/- 5.8 vs. 49.6 +/- 5.4) and ablation size (25.1 +/- 3.4 vs. 24.3 +/- 5.1) were not significantly different for controls (n = 8) and tumor-mimics (n = 26), respectively. One animal died of a pulmonary embolism following injection of agarose into a hepatic vein. The agarose-based tissue-mimic creates realistic sonographic targets for learning ultrasound-guided open and laparoscopic radiofrequency ablation in an in vivo model.