Radiofrequency ablation followed by resection of malignant liver tumors

Clinical translation of abdominal histotripsy: a review of preclinical studies in large animal models

Histotripsy is an emerging noninvasive, non-thermal, and non-ionizing focused ultrasound (US) therapy that can be used to destroy targeted tissue. Histotripsy has evolved from early laboratory prototypes to clinical systems which have been comprehensively evaluated in the preclinical environment to ensure safe translation to human use. This review summarizes the observations and results from preclinical histotripsy studies in the liver, kidney, and pancreas. Key findings from these studies include the ability to make a clinically relevant treatment zone in each organ with maintained collagenous architecture, potentially allowing treatments in areas not currently amenable to thermal ablation. Treatments across organ capsules have proven safe, including in anticoagulated models which may expand patients eligible for treatment or eliminate the risk associated with taking patients off anti-coagulation. Treatment zones are well-defined with imaging and rapidly resorb, which may allow improved evaluation of treatment zones for residual or recurrent tumor. Understanding the effects of histotripsy in animal models will help inform physicians adopting histotripsy for human clinical use.

Mechanical fractionation of tissues using microsecond-long HIFU pulses on a clinical MR-HIFU system

PURPOSE

High intensity focussed ultrasound (HIFU) can non-invasively treat tumours with minimal or no damage to intervening tissues. While continuous-wave HIFU thermally ablates target tissue, the effect of hundreds of microsecond-long pulsed sonications is examined in this work. The objective of this study was to characterise sonication parameter-dependent thermomechanical bioeffects to provide the foundation for future preclinical studies and facilitate clinical translation.

METHODS AND MATERIALS

Acoustic power, number of cycles/pulse, sonication time and pulse repetition frequency (PRF) were varied on a clinical magnetic resonance imaging (MRI)-guided HIFU (MR-HIFU) system. Ex vivo porcine liver, kidney and cardiac muscle tissue samples were sonicated (3 × 3 grid pattern, 1 mm spacing). Temperature, thermal dose and T2 relaxation times were quantified using MRI. Lesions were histologically analysed using H&E and vimentin stains for lesion structure and viability.

RESULTS

Thermomechanical HIFU bioeffects produced distinct types of fractionated tissue lesions: solid/thermal, paste-like and vacuolated. Sonications at 20 or 60 Hz PRF generated substantial tissue damage beyond the focal region, with reduced viability on vimentin staining, whereas H&E staining indicated intact tissue. Same sonication parameters produced dissimilar lesions in different tissue types, while significant differences in temperature, thermal dose and T2 were observed between the parameter sets.

CONCLUSION

Clinical MR-HIFU system was utilised to generate distinct types of lesions and to produce targeted thermomechanical bioeffects in ex vivo tissues. The results guide HIFU research on thermomechanical tissue bioeffects, inform future studies and advice sonication parameter selection for direct tumour ablation or immunomodulation using a clinical MR-HIFU system.

Real-time estimation of lesion depth and control of radiofrequency ablation within ex vivo animal tissues using a neural network

BACKGROUND

Radiofrequency ablation (RFA), a method of inducing thermal ablation (cell death), is often used to destroy tumours or potentially cancerous tissue. Current techniques for RFA estimation (electrical impedance tomography, Nakagami ultrasound, etc.) require long compute times (≥ 2 s) and measurement devices other than the RFA device. This study aims to determine if a neural network (NN) can estimate ablation lesion depth for control of bipolar RFA using complex electrical impedance - since tissue electrical conductivity varies as a function of tissue temperature - in real time using only the RFA therapy device's electrodes.

METHODS

Three-dimensional, cubic models comprised of beef liver, pork loin or pork belly represented target tissue. Temperature and complex electrical impedance from 72 data generation ablations in pork loin and belly were used for training the NN (403 s on Xeon processor). NN inputs were inquiry depth, starting complex impedance and current complex impedance. Training-validation-test splits were 70%-0%-30% and 80%-10%-10% (overfit test). Once the NN-estimated lesion depth for a margin reached the target lesion depth, RFA was stopped for that margin of tissue.

RESULTS

The NN trained to 93% accuracy and an NN-integrated control ablated tissue to within 1.0 mm of the target lesion depth on average. Full 15-mm depth maps were calculated in 0.2 s on a single-core ARMv7 processor.

CONCLUSIONS

The results show that a NN could make lesion depth estimations in real-time using less in situ devices than current techniques. With the NN-based technique, physicians could deliver quicker and more precise ablation therapy.

New Approaches in Locoregional Therapies for Hepatocellular Carcinoma

PURPOSE

Hepatocellular carcinoma (HCC) represent actually the fifth most common cancer worldwide, with liver transplantation and hepatic resection who represent the standard of care of curative treatment. Unfortunately, not all patient could benefit of curative treatment. For such patients, locoregional or systemic therapies represent a valid option in order to achieve the best survival possible.

METHODS

A review of most interesting paper actually present in literature on locoregional treatment for nonresectable nontransplantable HCC was performed.

RESULTS

A detailed description on each different approach has been detailed in each chapter.

CONCLUSION

In case of nontransplantable and nonresectable HCC, locoregional treatment represent a valid alternative in management of this patients.

Percutaneous Irreversible Electroporation: Long-term survival analysis of 71 patients with inoperable malignant hepatic tumors

Aim of this retrospective analysis was to evaluate the survival times after percutaneous irreversible electroporation (IRE) in inoperable liver tumors not amenable to thermal ablation. 71 patients (14 females, 57 males, median age 63.5 ± 10.8 years) with 103 liver tumors were treated in 83 interventions using IRE (NanoKnife® system). The median tumor short-axis diameter was 1.9 cm (minimum 0.4 cm, maximum 4.5 cm). 35 patients had primary liver tumors and 36 patients had liver metastases. The Kaplan-Meier method was employed to calculate the survival rates, and the different groups were compared using multivariate log-rank and Wilcoxon tests. The overall median survival time was 26.3 months; the median survival of patients with primary land secondary liver cancer did not significantly differ (26.8 vs. 19.9 months; p = 0.41). Patients with a tumor diameter >3 cm (p < 0.001) or more than 2 lesions (p < 0.005) died significantly earlier than patients with smaller or fewer tumors. Patients with hepatocellular carcinoma and Child-Pugh class B or C cirrhosis died significantly earlier than patients with Child-Pugh class A (p < 0.05). Patients with very early stage HCC survived significantly longer than patients with early stage HCC with a median survival of 22.3 vs. 13.7 months (p < 0.05).

Effect of thermal dose on heat shock protein expression after radio-frequency ablation with and without adjuvant nanoparticle chemotherapies

PURPOSE

The aim of this study was to evaluate the effect of different radio-frequency ablation (RFA) thermal doses on coagulation and heat shock protein (HSP) response with and without adjuvant nanotherapies.

MATERIALS AND METHODS

First, Fischer rats were assigned to nine different thermal doses of hepatic RFA (50-90 °C, 2-20 min, three per group) or no treatment (n = 3). Next, five of these RF thermal doses were combined with liposomal-doxorubicin (Lipo-Dox, 1 mg intravenously) in R3230 breast tumours, or no tumour treatment (five per group). Finally, RFA/Lipo-Dox was given without and with an Hsp70 inhibitor, micellar quercetin (Mic-Qu, 0.3 mg intravenously) for two different RFA doses with similar coagulation but differing peri-ablational Hsp70 (RFA/Lipo-Dox at 70 °C × 5 min and 90 °C × 2 min, single tumours, five per group). All animals were sacrificed 24 h post-RFA and gross tissue coagulation and Hsp70 (maximum rim thickness and % cell positivity) were correlated to thermal dose including cumulative equivalent minutes at 43 °C (CEM₄₃).

RESULTS

Incremental increases in thermal dose (CEM₄₃) correlated to increasing liver tissue coagulation (R² = 0.7), but not with peri-ablational Hsp70 expression (R² = 0.14). Similarly, increasing thermal dose correlated to increasing R3230 tumour coagulation for RF alone and RFA/Lipo-Dox (R² = 0.7 for both). The addition of Lipo-Dox better correlated to increasing Hsp70 expression compared to RFA alone (RFA: R² = 0.4, RFA/Lipo-Dox: R² = 0.7). Finally, addition of Mic-Qu to two thermal doses combined with Lipo-Dox resulted in greater tumour coagulation (p < 0.0003) for RFA at 90 °C × 2 min (i.e. greater baseline Hsp70 expression) than an RFA dose that produced similar coagulation but less HSP expression (p < 0.0004).

CONCLUSION

Adjuvant intravenous Lipo-Dox increases peri-ablational Hsp70 expression in a thermally dependent manner. Such expression can be exploited to produce greater tumour destruction when adding a second adjuvant nanodrug (Mic-Qu) to suppress peri-ablational HSP expression.

Efficacy of additional radiofrequency ablation after transcatheter arterial chemoembolization for intermediate hepatocellular carcinoma

AIM

For intermediate hepatocellular carcinoma (HCC), transcatheter arterial chemoembolization (TACE) therapy is recommended in the guidelines as a monotherapy, although TACE is a non-curative therapy. The aims of the present study were to evaluate the efficacy of adding radiofrequency ablation (RFA) to TACE in patients with intermediate HCC, and to identify the factors that were associated with favorable survival in these patients.

METHODS

Fifty-nine patients with intermediate HCC were enrolled in this retrospective study. Thirty-nine patients were treated with TACE alone and 20 patients were treated with additional RFA after TACE.

RESULTS

The recurrence-free survival rates at 0.5, 1 and 2 years for the additional RFA group were 32%, 19% and 13%, respectively, and these were significantly higher than those of the TACE group (8%, 3% and 0%, respectively; log-rank test, P = 0.001). The cumulative survival rates of the additional RFA group were significantly higher than those of the TACE group (log-rank test, P = 0.002), although this significant difference was not found in the subgroup of treatment naive patients because of small sample size. Multivariate analysis indicated male sex, lower total bilirubin, lower α-fetoprotein, lower des-γ-carboxyprothrombin, newly recurrent HCC nodules within the last 12 months and additional RFA as independent factors that were significantly associated with favorable overall survival.

CONCLUSION

Additional RFA of nodules insufficiently treated by TACE is effective therapy for obtaining favorable disease-free survival in patients with intermediate HCC, and leads to better overall survival particularly in recurrent patients.

Effect of liver regeneration on malignant hepatic tumors

Liver regeneration after major surgery may activate occult micrometastases and facilitate tumor growth, leading to liver tumor recurrence. Molecular changes during liver regeneration can provide a microenvironment that stimulates intrahepatic tumor propagation through alterations in cellular signaling pathways, where activation and proliferation of mature hepatocytes, hepatic progenitor cells, non-parenchymal liver cells might favor both liver regeneration and tumor growth. This review highlights recent advances of tumor growth and development in the regenerating liver, possible mechanisms and clinical implications.

Totally laparoscopic strategies for the management of colorectal cancer with synchronous liver metastasis

INTRODUCTION

Laparoscopy is an accepted treatment for colorectal cancer and liver metastases, but there is no consensus for its use in the management of synchronous liver metastases (SCRLM). The purpose of this study was to evaluate totally laparoscopic strategies in the management of colorectal cancer with synchronous liver metastases.

METHODS

Patients presenting to Ninewells Hospital between July 2007 and August 2010, with adenocarcinoma of the colon and rectum with synchronous liver metastases were considered. Patients underwent simultaneous laparoscopic liver and colon cancer resection, a staged laparoscopic resection of SCRLM and colon cancer, or simultaneous colon resection and radiofrequency ablation (RFA) of SCRLM. Primary endpoints were in-hospital morbidity and mortality, total hospital stay, intraoperative blood loss, duration of surgery, and resection margin status.

RESULTS

Twenty-eight patients presented with synchronous colorectal liver metastases. Thirteen patients underwent a simultaneous laparoscopic liver and colon resection (median operating time, 370 (range, 190-540) min; median hospital stay, 7 (range, 3-54) days), seven patients had a staged laparoscopic resection of SCRLM and primary colon cancer (median operating time, 530 (range, 360-980) min; median hospital stay 14, (range, 6-51) days), and eight patients underwent laparoscopic colon resection and RFA of SCRLM (median operating time, 310 (range, 240-425) min; median hospital stay, 8 (range, 6-13) days). There were no conversions to an open procedure. Overall in-hospital morbidity and mortality was 28 and 0 % respectively. An R0 resection margin was achieved in 91 % of the resection group. At a median follow-up of 26 (range, 18-55) months, 19 (90 %) patients remain disease-free.

CONCLUSIONS

Totally laparoscopic strategies for the radical treatment of stage IV colorectal cancer are feasible with low morbidity and favorable outcomes. A laparoscopic approach for the simultaneous management of SCRLM and primary colon cancer is associated with reduced surgical access trauma, postoperative morbidity, and hospital stay with no compromise in short-term oncological outcome.

Totally laparoscopic strategies for the management of colorectal cancer with synchronous liver metastasis

INTRODUCTION

Laparoscopy is an accepted treatment for colorectal cancer and liver metastases, but there is no consensus for its use in the management of synchronous liver metastases (SCRLM). The purpose of this study was to evaluate totally laparoscopic strategies in the management of colorectal cancer with synchronous liver metastases.

METHODS

Patients presenting to Ninewells Hospital between July 2007 and August 2010, with adenocarcinoma of the colon and rectum with synchronous liver metastases were considered. Patients underwent simultaneous laparoscopic liver and colon cancer resection, a staged laparoscopic resection of SCRLM and colon cancer, or simultaneous colon resection and radiofrequency ablation (RFA) of SCRLM. Primary endpoints were in-hospital morbidity and mortality, total hospital stay, intraoperative blood loss, duration of surgery, and resection margin status.

RESULTS

Twenty-eight patients presented with synchronous colorectal liver metastases. Thirteen patients underwent a simultaneous laparoscopic liver and colon resection (median operating time, 370 (range, 190-540) min; median hospital stay, 7 (range, 3-54) days), seven patients had a staged laparoscopic resection of SCRLM and primary colon cancer (median operating time, 530 (range, 360-980) min; median hospital stay 14, (range, 6-51) days), and eight patients underwent laparoscopic colon resection and RFA of SCRLM (median operating time, 310 (range, 240-425) min; median hospital stay, 8 (range, 6-13) days). There were no conversions to an open procedure. Overall in-hospital morbidity and mortality was 28 and 0 % respectively. An R0 resection margin was achieved in 91 % of the resection group. At a median follow-up of 26 (range, 18-55) months, 19 (90 %) patients remain disease-free.

CONCLUSIONS

Totally laparoscopic strategies for the radical treatment of stage IV colorectal cancer are feasible with low morbidity and favorable outcomes. A laparoscopic approach for the simultaneous management of SCRLM and primary colon cancer is associated with reduced surgical access trauma, postoperative morbidity, and hospital stay with no compromise in short-term oncological outcome.

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

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

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.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Heat shock protein 70 expression following hepatic radiofrequency ablation is affected by adjacent vasculature

BACKGROUND

Heat shock proteins are a highly conserved family of stress response proteins. Members of the heat shock protein 70 (Hsp70) family prevent protein misfolding and aggregation. Following radiofrequency ablation of unresectable liver tumors an interface appears between the irreversibly damaged and normal liver. The fate of this transition zone is critical and is believed to be responsible for local recurrences. Hsp70 is expressed in response to thermal stress and may influence the fate of cells in this transitional zone. It is also recognized that the presence of large vessels or a perivascular location of tumors also influences the recurrence rate. The aim of this study is to examine the transition zone and observe the effect of local blood flow on ablation morphology and Hsp70 expression.

METHODS

Radiofrequency ablation was performed in 25 rats at various distances from the liver hilum. Tissue was retrieved and analysed at time points 0, 4, 24, 48 h, and 2 wk following treatment. Tissue was analyzed histologically with hematoxylin and eosin staining (H and E,) and immunohistochemically for Hsp70 expression.

RESULTS

All rats survived the procedure. H and E staining revealed previously unreported foci of apoptosis at the ablation edge and deep in the normal hepatic parenchyma. Hsp70 was expressed in the transition zone at 4 h and peaked at 24 h. The degree of Hsp70 expression was significantly influenced by the distance from surrounding vasculature.

CONCLUSIONS

This study reports several previously unreported findings. There is increased apoptosis distal to the ablated zone suggests leakage of radiofrequency (RF) current down blood vessels originating in the ablation zone. The degree of Hsp70 expression in the transition zone correlates with time after treatment and the size and location of any adjacent vasculature. These findings suggest that heat shock proteins may play a role in the ability of damaged cells to recover and survive at the periphery of an ablation zone.

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.

Liver ablation techniques: a review

BACKGROUND

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

METHODS

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

RESULTS AND CONCLUSION

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

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

OBJECTIVE

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

SUMMARY BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Microbubbles in the pulmonary artery generated during experimental hepatic radiofrequency ablation is correlated with increased pulmonary arterial pressure

PURPOSE

Microbubbles in hepatic veins during hepatic radiofrequency (RF) ablation is a well-known observation. In this experimental study, we examined the association between microbubbles in the pulmonary artery and alterations in mean pulmonary arterial pressure (MPAP) during hepatic RF ablation with a perfusion electrode system.

MATERIALS AND METHODS

Sixteen domestic pigs were included in the study. Twelve animals were randomly assigned to RF ablation with maintained (n = 6) or interrupted (n = 6) hepatic inflow. Four animals were assigned to a control group where interruption of hepatic inflow but no RF ablation was performed. Microbubbles in the pulmonary artery were recorded by transesophageal echocardiography and scored according to the number of bubbles per heart cycle. Mean pulmonary arterial pressure was continuously registered by a pulmonary artery catheter. The association between the microbubble score and increase in MPAP during ablation was examined using Spearman's rank correlation coefficient.

RESULTS

Echocardiographic recordings were acquired in 9 of 12 animals in the two treatment groups. Microbubbles in the pulmonary artery were present in four animals in each treatment group. Mean pulmonary arterial pressure increased from a baseline value of 17.7 mm Hg +/- 2.3 to a maximum value of 29.7 mm Hg +/- 7.7 during ablation (P = .018). A significant association was found between the microbubble score and increase in MPAP (P = .001).

CONCLUSIONS

Microbubbles were detected in the pulmonary artery during hepatic RF ablation both during maintained and interrupted hepatic inflow. A strong association was found between microbubbles in the pulmonary artery and increased MPAP. The clinical implications of our findings are to be determined.

Inoperable colorectal liver metastases: a declining entity?

BACKGROUND

Untreated colorectal liver metastases (CLMs) have a dismal prognosis. Surgery remains the gold standard of treatment, but many patients will have inoperable disease at presentation. Until recently, the outlook for such patients was bleak. The purpose of this review was to report on available options in the treatment CLMs, which would be considered unresectable by conventional evaluation.

METHODS

Inclusion criteria were articles published in English-language journals reporting on either retrospective or prospective cohorts of patients undergoing treatment for conventionally inoperable CLM. Main outcome measures were survival, resectability rates, morbidity and mortality following treatment of the patients' disease.

RESULTS

Improved chemotherapy regimes and other innovative treatments have opened up new options for such patients and may even render conventionally inoperable disease resectable. The aim of treatment should be down-staging of metastases to achieve resectability, however, other treatments such as ablation may be also be used (either alone or in conjunction with resection).

CONCLUSION

A nihilistic attitude to the patient with seemingly inoperable liver metastases should be discouraged. Discussion of such patients at multi-disciplinary meetings is essential in order to plan and monitor treatments.

A radiofrequency-assisted device for bloodless rapid transection of the liver: A comparative study in a pig liver model

BACKGROUND

Efficient and safe liver parenchymal transection is dependent on the ability to address both parenchymal division and hemostasis simultaneously. In this article we describe and compare with a saline-linked instrument a new radiofrequency (RF)-assisted device specifically designed for tissue thermocoagulation and division of the liver used on an in vivo pig liver model.

METHODS

In total, 20 partial hepatectomies were performed on pigs through laparotomy. Two groups were studied: group A (n=8) with hepatectomy performed using only the proposed RF-assisted device and group B (n=8) with hepatectomy performed using only a saline-linked device. Main outcome measures were: transection time, blood loss during transection, transection area, transection speed and blood loss per transection area. Secondary measures were: risk of biliary leakage, tissue coagulation depth and the need for hemostatic stitches. Tissue viability was evaluated in selected samples by staining of tissue NADH.

RESULTS

In group A both blood loss and blood loss per transection area were lower (p=0.001) than in group B (70+/-74 ml and 2+/-2 ml/cm(2) vs. 527+/-273 ml and 13+/-6 ml/cm(2), for groups A and B, respectively). An increase in mean transection speed when using the proposed device over the saline-linked device group was also demonstrated (3+/-0 and 2+/-1cm(2)/min for group A and B, respectively) (p=0.002). Tissue coagulation depth was greater (p=0.005) in group A than in group B (6+/-2 mm and 3+/-1 mm, for groups A and B, respectively). Neither macroscopic nor microscopic differences were encountered in transection surfaces between both groups.

CONCLUSIONS

The proposed RF-assisted device was shown to address parenchymal division and hemostasis simultaneously, with less blood loss and faster transection time than saline-linked technology in this experimental model.

Insufficient radiofrequency ablation therapy may induce further malignant transformation of hepatocellular carcinoma

BACKGROUND

Radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC) is a thermoablative technique to kill tumor tissue by generating areas of coagulative necrosis. Recent reports have raised concern that RFA may lead to a local recurrence of HCC with an aggressive phenotype and unfavorable prognosis, suggesting that RFA may induce further malignant transformation of HCC. However, the biological effects of RFA on HCC cells have not been directly analyzed. The aim of this study was to determine whether heat stress of the type associated with RFA induces malignant transformation of HCC.

METHODS

We assessed the sensitivity of three HCC cell lines (HepG2, Alexander, and Huh7) to heat treatment for 10 min. We then determined the temperature at which a heat-resistant subline can be generated. We established and expanded sublines that survived heat treatment. And their proliferation rates, heat sensitivities, and invasive capacities were further examined.

RESULTS

All HepG2 died after 48 degrees C treatment, whereas 49 degrees C treatment was required to kill all Alexander and HuH7. We generated 20 sublines for each parental cell line. A HepG2 subline, HepG2#18, proliferated 100% faster than parental HepG2. Moreover, HepG2#18 survived after 50 degrees C treatment, whereas all parental HepG2 died after heat treatments at 48 degrees C or higher.

CONCLUSION

Our results showed that even a single heat treatment could induce further transformation of an HCC cell line. Our results suggest that an insufficient treatment of HCC by RFA that enables survival of some cells might induce further malignant transformation in vivo.

New horizons in MR-controlled and monitored radiofrequency ablation of liver tumours

There is a sustained interest in using magnetic resonance (MR) thermometry to monitor the radiofrequency ablation of liver tumours as a means of visualizing the progress of the thermal coagulation and deciding the optimal end-point. Despite numerous technical challenges, important progress has been made and demonstrated in animal studies. In addition to MR thermometry, MR can now be used for the guidance of the tumour targeting with ‘fluoroscopic’ rapid image acquisition, and it can provide several contrast mechanisms for post-procedural assessment of the extent of the thermal coagulation zone. Challenges of in vivo simultaneous MR thermometry implementation and the current limitations of the thermal dose model for the estimation of the extent of the thermal coagulation zone are discussed. MR imaging could enhance the success of RF ablation of liver tumours due to its potential to provide accurate targeting, monitoring, and post-procedural evaluation.

Influence de la proximité des gros vaisseaux sur les résultats du traitement des carcinomes hépato-cellulaires par radiofréquence : une étude contrôlée

PURPOSE

To evaluate the risk of radiofrequency ablation treatment failure for hepatocellular carcinomas (HCC) next to large vessels.

MATERIALS AND METHODS

Between May 2000 and October 2002, from a total of 83 patients treated by radiofrequency ablation for HCC in a single center, 13 patients with tumor<or=3.5 cm contacting a vessel >or=3 mm in diameter (Group A) were matched with 13 patients with similar size tumors located away from large vessels (Group B). Immediate response and recurrence rate were evaluated on CT.

RESULTS

After mean follow-up interval of 39+/-16.5 months for Group A and 39+/-14 months for Group B, local recurrence rates were 7/12 versus 1/12 respectively (p=0.03). For Group A, 6/7 local recurrences clearly contacted a large vessel.

CONCLUSION

The cooling effect from flowing blood in large vessels markedly increases the rate of local failure of radiofrequency ablation for small HCC located near large vessels.

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

INTRODUCTION

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSION

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

Rates and patterns of recurrence for percutaneous radiofrequency ablation and open wedge resection for solitary colorectal liver metastasis

INTRODUCTION

The purpose of this study was to compare rates and patterns of disease progression following percutaneous, image-guided radiofrequency ablation (RFA) and nonanatomic wedge resection for solitary colorectal liver metastases.

METHODS

We identified 30 patients who underwent nonanatomic wedge resection for solitary liver metastases and 22 patients who underwent percutaneous RFA because of prior major hepatectomy (50%), major medical comorbidities (41%), or relative unresectability (9%). Serial imaging studies were retrospectively reviewed for evidence of local tumor progression.

RESULTS

Patients in the RFA group were more likely to have undergone prior liver resection, to have a disease-free interval greater than 1 year, and to have had an abnormal carcinoembryonic antigen (CEA) level before treatment. Two-year local tumor progression-free survival (PFS) was 88% in the Wedge group and 41% in the RFA group. Two patients in the RFA group underwent re-ablation, and two patients underwent resection to improve the 2-year local tumor disease-free survival to 55%. Approximately 30% of patients in each group presented with distant metastasis as a component of their first recurrence. Median overall survival from the time of resection was 80 months in the Wedge group vs 31 months in the RFA group. However, overall survival from the time of treatment of the colorectal primary was not significantly different between the two groups.

CONCLUSIONS

Local tumor progression is common after percutaneous RFA. Surgical resection remains the gold standard treatment for patients who are candidates for resection. For patients who are poor candidates for resection, RFA may help to manage local disease, but close follow-up and retreatment are necessary to achieve optimal results.

Radiofrequency ablation of rabbit liver in vivo: effect of the pringle maneuver on pathologic changes in liver surrounding the ablation zone

Objective

We wished to evaluate the effect of the Pringle maneuver (occlusion of both the hepatic artery and portal vein) on the pathologic changes in the hepatic vessels, bile ducts and liver parenchyma surrounding the ablation zone in rabbit livers.

Materials and Methods

Radiofrequency (RF) ablation zones were created in the livers of 24 rabbits in vivo by using a 50-W, 480-kHz monopolar RF generator and a 15-gauge expandable electrode with four sharp prongs for 7 mins. The tips of the electrodes were placed in the liver parenchyma near the porta hepatis with the distal 1 cm of their prongs deployed. Radiofrequency ablation was performed in the groups with (n=12 rabbits) and without (n=12 rabbits) the Pringle maneuver. Three animals of each group were sacrificed immediately, three days (the acute phase), seven days (the early subacute phase) and two weeks (the late subacute phase) after RF ablation. The ablation zones were excised and serial pathologic changes in the hepatic vessels, bile ducts and liver parenchyma surrounding the ablation zone were evaluated.

Results

With the Pringle maneuver, portal vein thrombosis was found in three cases (in the immediate [n=2] and acute phase [n=1]), bile duct dilatation adjacent to the ablation zone was found in one case (in the late subacute phase [n=1]), infarction adjacent to the ablation zone was found in three cases (in the early subacute [n=2] and late subacute [n=1] phases). None of the above changes was found in the livers ablated without the Pringle maneuver. On the microscopic findings, centrilobular congestion, sinusoidal congestion, sinusoidal platelet and neutrophilic adhesion, and hepatocyte vacuolar and ballooning changes in liver ablated with Pringle maneuver showed more significant changes than in those livers ablated without the Pringle maneuver (p < 0.05)

Conclusion

Radiofrequency ablation with the Pringle maneuver created more severe pathologic changes in the portal vein, bile ducts and liver parenchyma surrounding the ablation zone compared with RF ablation without the Pringle maneuver. Therefore, we suggest that RF ablation with the Pringle maneuver should be performed with great caution in order to avoid unwanted thermal injury.

Experimental study on microwave tissue coagulation of canine pancreas

AIM: To evaluate the feasibility and safety of microwave tissue coagulation to pancreas through the observation of physiological state and pathological changes after the coagulation of canine pancreas.

METHODS: Microwave tissue coagulation of fifteen healthy mongrel dogs' pancreas was performed hrough laparotomy. The power and time were set on 50 Watt and three minutes respectively. The 5 coagulated points were selected at an interval of 1 cm. The blood amylase and other parameters were examined regularly after the operation. The dogs were killed at the instant time (n = 5), the 1^st d (n = 5) and 1^st wk (n = 5) after the operation. Hematoxylin and eosin (HE) staining together with nicotinamide adenine dinucleotide (NADH) and TUNEL staining was used to observe the pathological changes.

RESULTS: The level of blood amylase increased immediately after the operation and the maximal value occurred within 48-72 h. Furthermore, it returned to normal level 1 wk later if no complications occurred. The segmental microwave lesions included hyperintense zone of coagulative necrosis and peripheral hypointense zone. Apoptosis was observed at the peripheral zone 1 d after the operation. The fibrosis and tissue absorption occurred finally 1 wk after the operation.

CONCLUSION: Microwave tissue coagulation is safe and feasible, and it may be used in the treatment of pancreatic cancer at the late stage.

Percutaneous radiofrequency ablation of lung tumors with expandable needle electrodes: current status

Percutaneous radiofrequency thermal ablation (RFA) has been used to treat primary and secondary liver tumors under ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI) guidance for the past decade [Park et al., Radiol Clin North Am 38:545-561, 2000; Siperstein and Gotomirski, Cancer J 6:S293-S301, 2000; Kelekis et al., Eur Radiol 13:1100-1105, 2003]. RFA is a low-cost, minimally invasive treatment that has recently attracted attention for treating tumors in different solid organs with promising results [Dupuy and Goldberg, J Vasc Interv Radiol 12:1135-1148, 2001; Friedman et al., Cardiovasc Intervent Radiol 27:427-434, 2004]. It can be provided with minimal hospitalization, and experienced practitioners have reported low complication rates [Dupuy and Goldberg, J Vasc Interv Radiol 12:1135-1148, 2001; Livraghi et al., Radiology 226:441-451, 2003]. Patients with lung malignancies (primary lung cancer or pulmonary metastases), who cannot be operated, might be candidates for RFA treatment. It can also be used in association with other treatments (i.e., chemotherapy, radiotherapy) for better disease control. Combination of the above with RFA may help reduce morbidity and mortality. Many ways to apply energy to the tumor exist (monopolar and bipolar RFA, microwave, laser, brachytherapy). In this review we will focus on expandable monopolar systems, which despite their deficiencies are the most popular in the interventional radiology sector.

Intraoperative Radiofrequency Ablation Using a Loop Internally Cooled-Perfusion Electrode: In Vitro and In Vivo Experiments

OBJECTIVE

We sought to validate the efficiency of intraoperative radiofrequency ablation (RFA) using a prototype loop internally cooled-perfusion (LICP) electrode to induce coagulation in the subcapsular portion of the liver.

MATERIALS AND METHODS

In in vitro experiments, 30 ablation regions were created using a 200-W generator and a LICP electrode featured simultaneous intraelectrode cooling and continuous flow of hypertonic saline along the shaft in explanted bovine liver. In the in vivo experiments, 26 ablation zones were created according to one of the five protocols in 10 dogs: group A, RFA using a cooled-tip electrode (n = 6); group B, RFA using a LICP electrode with 2 cm loop tip (n = 6); group C, RFA using a LICP electrode with a 3-cm loop tip (n = 6); group D, RFA using a cooled-tip electrode and Pringle maneuver (n = 4); and group E, RFA using a LICP electrode with 2 cm loop tip and Pringle maneuver (n = 4). The dimensions of the coagulation parameters were compared between the groups.

RESULTS

In the in vitro experiments, RFA using a 2- or 3-cm diameter LICP electrode (3.6 +/- 0.3 cm, 3.4 +/- 0.5 cm, respectively) created deeper dimensions of coagulation than did a 4-cm electrode (2.3 +/- 0.2 cm; P < 0.05). In the in vivo experiments, the RFA using the LICP electrodes in porcine liver with normal perfusion induced wider but superficial ablation regions when compared to standard RFA using an internally cooled electrode (P < 0.05). However, using a Pringle maneuver, RFA with a LICP electrode created a larger volume of ablation area when compared to RFA using an internally cooled electrode with a similar range of axial diameter along the electrode axis: 30.0 +/- 6.1 cm3 (group D) versus 68.5 +/- 14.0 cm3 (group E; P < 0.05)

CONCLUSIONS

Intraoperative RFA using the LICP electrode induced a well-defined semicircular coagulation with a 3.5-cm axial diameter in the subcapsular region of the liver. This device appears to be promising for the treatment of superficial tumors during intraoperative RFA.

Radiofrequency thermal ablation of liver carcinoma

OBJECTIVES

The aim of this prospective study was to evaluate the feasibility of radiofrequency ablation of hepatic tumors. We studied the rates of mortality, morbidity, and recurrence and recorded overall and disease-free survival.

METHODS

All patients aged over 18 years with histologically proven malignant liver disease inaccessible to surgical treatment (one to four tumor localizations) were eligible for inclusion in the study. Child-Pugh score > B9, platelets count <or=50.103/mm3, prothrombin index <or=50% and pregnancy were exclusion factors.

RESULTS

Between July 2001 and June 2004, 51 patients (13 women, 38 men, mean age 66 +/- 9 years) were included and underwent 61 radiofrequency thermal ablation procedures for 82 hepatic lesions: hepatocarcinoma (N=44), cholangiocarcinoma (N=1), metastasic tumors (N=37). Hospital morbidity and mortality were 11.5% and 2% respectively. Recurrence rate at 3 years was 20.6%. In multivariate analysis, only tumor size > 3 cm was correlated significantly with recurrence (P=0.03). Actuarial 1-, 2- and 3-year survival rates in the hepatocarcinoma group (N=31) were 84.7%, 57.7% and 34.6% respectively. Actuarial 1-, 2- and 3-year survival rates in the metastasis from colorectal adenocarcinoma group (N=14) were 90%, 54% and 54% respectively (P=0.72).

CONCLUSION

Radiofrequency thermal ablation is an effective treatment for hepatic tumors measuring less than 3 cm. There is a low risk of complications and open surgery can be associated. However in the absence of randomized studies comparing radiofrequency and surgery, respective indications cannot be defined in detail.

A review of the general aspects of radiofrequency ablation

As an alternative to standard surgical resection for the treatment of malignant tumors, radiofrequency ablation (RFA) has rapidly evolved into the most popular minimally invasive therapy. To help readers gain the relevant background knowledge and to better understand the other reviews in this Feature Section on the clinical applications of RFA in different abdominal organs, the present report covers the general aspects of RFA. After an introduction, we present a simple definition of the energy applied during RFA, a brief historical review of its technical evolution, and an explanation of the mechanism of action of RFA. These basic discussions are substantiated with descriptions of RFA equipment including those commercially available and those under preclinical development. The size and geometry of induced lesions in relation to RFA efficacy and side effects are discussed. The unique pathophysiologic process of thermal tissue damage and the corresponding histomorphologic manifestations after RFA are detailed and cross-referenced with the findings in the current literature. The crucial role of imaging technology during and after RFA is also addressed, including some promising new developments. This report finishes with a summary of the key messages and a perspective on further technologic refinements and identifies some specific priorities.

Combined Tumor Therapy by Using Radiofrequency Ablation and 5-FU–Laden Polymer Implants: Evaluation in Rats and Rabbits

PURPOSE

To evaluate the use of 5-fluorouracil (5-FU)-laden polymer implants as an adjunct to radiofrequency (RF) ablation for tumor treatment.

MATERIALS AND METHODS

All animal studies were performed in compliance with the Case Western Reserve University Institutional Animal Care and Use Committee guidelines. Three studies were performed to investigate (a) in vitro dissolution of 5-FU-laden polymer implants in saline and bovine serum, (b) tissue distribution of 5-FU and its metabolite, 5-fluorouridine (5-FUrd), in the ablated liver tissue of rats (n = 4), and (c) efficacy of combined approach (n = 4) compared with that of ablation alone (n = 6) for VX2 liver tumor model in rabbits. Characterization of 5-FU release in vitro and distribution of 5-FU in rat liver tissue were analyzed by using high performance liquid chromatography; in vivo efficacy was assessed by using computed tomography and pathologic examination.

RESULTS

Results of the in vitro dissolution study showed that a 75% release of 5-FU occurred in 2 days when exposed to bovine serum and in 9 days when exposed to phosphate-buffered saline. In the ablated rat liver, the 5-FU level was higher at the center and lower at the periphery of the tissue both at 24 hours (41.0 mg per kilogram tissue vs 15.0 mg per kilogram tissue, respectively) and at 48 hours (8.0 mg per kilogram tissue vs 2.0 mg per kilogram tissue, respectively). The 5-FUrd concentration was twofold higher peripherally than centrally and was higher at 48 hours than at 24 hours. In rabbits, local delivery of 5-FU immediately after RF ablation provided a significant (P < .05) reduction in tumor size compared with ablation alone (1.80 cm3 +/- 0.28 [standard error] vs 3.53 cm3 +/- 0.52, respectively; P = .034) and a more than 20-fold reduction in tumor size compared with the control (1.80 cm3 +/- 0.28 vs 41.95 cm3 +/- 11.58, respectively; P = .018).

CONCLUSION

Combined treatment by using 5-FU polymer implants and RF ablation shows uniform sustained release of 5-FU for 48 hours at least 8 mm from the edge of the ablation zone and appears to be successful at controlling the growth of an experimental tumor in rabbits appreciably better than does ablation alone.

Short- and-long term results of intraoperative radiofrequency ablation of liver metastases

BACKGROUND

Surgical resection is the only therapeutic option with curative effect on malignant liver tumours, but in over 70% of cases, this is not a feasible option. A prospective study was performed to assess the short- and long-term effects of intraoperative radiofrequency ablation on unresectable liver metastases.

PATIENTS

Between 1997 and 2001, 57 patients (mean age 61.9 years; range 31-83 years) with 297 unresectable liver metastases (colorectal adenocarcinoma, n=38; carcinoid tumour, n=4; malignant melanoma, n=3; other metastases, n=12) underwent intraoperative radiofrequency ablation.

RESULTS

No mortality was observed in patients managed solely with radiofrequency ablation. Eight postoperative complications occurred in eight patients (14%). Three occurred when radiofrequency ablation was combined with resection. Of the 33 patients completely ablated, 30 patients are still alive and 21 are disease-free after a median follow-up of 18.1 months (range 2-43). Ten patients underwent more than one intraoperative radiofrequency ablation episode. Overall survival was 72.5% at 1 year and 52.5% at 3 years. Complete ablation and the number of lesions were significant independent prognostic factors for survival, with p<0.001 and p<0.0001, respectively.

CONCLUSION

Radiofrequency ablation is a safe and effective option for patients with inoperable liver metastases without extra hepatic disease. Prospective controlled trials comparing the results of different treatments are required to assess which patients will benefit best from this emerging new treatment.

Image guided tumour ablation

Several different technologies have been employed for the local ablation of tissue by thermal techniques. At the present time the most widely favoured technique is radiofrequency ablation (RFA) but developments in other techniques, e.g. microwave may change this. In many countries RFA or percutaneous ethanol injection (PEI) are accepted therapies for patients with Childs Pugh Class A or B cirrhosis and early hepatocellular carcinoma (HCC). Results for RFA in large series of patients with liver metastases from colon cancer are very promising. Five-year survival rates of 26% from the time of first ablation and 30% from the diagnosis of liver metastases for patients with limited (<6, <5 cm) liver disease who are not surgical candidates compares well with post resection series where 5-year survival rates vary between 29% and 39% in operable candidates. Sufficient experience has now been gained in lung and renal ablation to show that these are minimally invasive techniques which can produce effective tumour destruction with a limited morbidity. More novel areas for ablation such as adrenal or pelvic recurrence are being explored.

Local recurrence after hepatic radiofrequency coagulation: multivariate meta-analysis and review of contributing factors

OBJECTIVE

The purpose of this study was to analyze the factors that influence local recurrence after radiofrequency coagulation of liver tumors.

SUMMARY BACKGROUND DATA

Local recurrence rate varies widely between 2% and 60%. Apart from tumor size as an important risk factor for local recurrence, little is known about the impact of other factors.

METHODS

An exhaustive literature search was carried out for the period from January 1, 1990 to January 1, 2004. Only series with a minimal follow-up of 6 months and/or mean follow-up of 12 months were included. Univariate and multivariate meta-analyses were carried out.

RESULTS

Ninety-five independent series were included, allowing the analysis of the local recurrence rate of 5224 treated liver tumors. In a univariate analysis, tumor-dependent factors with significantly less local recurrences were: smaller size, neuroendocrine metastases, nonsubcapsular location, and location away from large vessels. Physician-dependent favorable factors were: surgical (open or laparoscopic) approach, vascular occlusion, general anesthesia, a 1-cm intentional margin, and a greater physician experience. In a multivariate analysis, significantly less local recurrences were observed for small size (P < 0.001) and a surgical (versus percutaneous) approach (P < 0.001).

CONCLUSIONS

Radiofrequency coagulation by laparoscopy or laparotomy results in superior local control, independent of tumor size. The percutaneous route should mainly be reserved for patients who cannot tolerate a laparoscopy or laparotomy. The short-term benefits of less invasiveness for the percutaneous route do not outweigh the longer-term higher risk of local recurrence.

Cancer cell dissemination during curative surgery for colorectal liver metastases

AIM

The amount of cancer cells disseminated during curative surgery for colorectal liver metastases (CRLM) may be responsible for recurrence. Haematogenous and intrahepatic cancer cell dissemination was evaluated, and its impact on cancer recurrence was assessed.

METHOD

Twenty patients with resectable CRLM were included in a prospective study. Twelve patients underwent curative resection for 21 metastases. Ten selected metastases in eight patients were treated with radiofrequency ablation (RFA) followed by resection at the same operative session. Cancer cell dissemination was determined before, during and after surgery using 'real time' quantitative RT-PCR assay, based on detection and quantification of CEA and CK20 mRNA transcripts.

RESULTS

Circulating cancer cells were detected in 80% and intrahepatic cancer cells in 37% of the patients, though without impact on cancer recurrence. The amounts of disseminated cancer cells were significantly increased after surgery. This increase was similar in patients treated with and without RFA. RFA caused complete tumour destruction.

CONCLUSION

Curative surgery for CRLM significantly increases the amount of disseminated cancer cells. Radiofrequency ablation can completely destroy selected resectable CRLM without excessive cancer cell dissemination. Neither haematogenous nor intrahepatic cancer cell dissemination were related to cancer recurrence in this small patient series.

Results of radio frequency ablation of primary and secondary liver tumors: long-term follow-up with computed tomography and positron emission tomography-18F-deoxyfluoroglucose scanning

BACKGROUND

In the literature, promising results have been obtained with radiofrequency ablation (RFA) of primary liver malignancies (e.g. hepatocellular carcinoma, HCC) and secondary liver malignancies (e.g. metastases of colorectal tumors). In our center, positron emission tomography with FDG (FDG-PET) and computed tomography (CT) were used for follow-up. Patient outcome was compared with that in the literature, and PET and CT were analyzed regarding positive and negative predictive values for early detection of tumor recurrence.

METHODS

The data were analyzed of patients who were treated with RFA for primary or secondary liver tumors between January 1999 and December 2002. Indications for treatment with RFA were liver tumors that could not be resected owing to size, number, or tumor location. In all patients, a CT scan was performed before RFA, and follow-up was performed with a CT scan in all patients and with an additional PET scan at various intervals in 11 patients. At evaluation with PET, tumor recurrence was defined as positive uptake of tracer either at the previous RFA lesion or at a new site in the liver.

RESULTS

In total, 15 patients (8 M, 7 F) were treated in 21 sessions with RFA. The mean follow-up period was 16.8 months (range: 7-42). Average age of the patients was 63 years (range: 40-74). One patient had a primary liver tumor; all other patients had metastases of the breast (1), ovary (1), renal cells (1), and colorectal carcinoma (11 patients). The mean number of tumors per patient was 2.7 (range: 1-5). No treatment-related morbidity or mortality occurred. In 4 of 11 patients evaluated with PET at a mean period of 6.8 months, positive uptake of tracer was noted. At CT evaluation, tumor recurrence was observed in 4 of these patients, at a mean time of 9.8 months. Two patients (13.3%) died of cancer recurrence during follow-up.

CONCLUSIONS

Tumor recurrence is comparable with that in other studies. Centrally located tumors showed more recurrence than peripheral tumors. The use of PET in combination with CT scan at follow-up may lead to earlier detection of tumor recurrence than contrast-enhanced CT alone.

Development and validation of an experimental model for the assessment of radiofrequency ablation of pancreatic parenchyma

OBJECTIVES

The aim of this study was to develop and validate an ex vivo model for the assessment of radiofrequency (RF) ablation of the pancreas.

METHODS

Porcine pancreata were used within 1 hour of sacrifice. RF was delivered to a premarked area in the center of the pancreatic head using a thermocouple-tipped multiprobe array. Four temperature presets were evaluated: 70 degrees-100 degrees C in 10 degrees increments. Immediately after ablation serial sections of the pancreatic head were cut to incorporate duodenum, portal vein, and bile duct. For each experiment, a portion of pancreatic tail was sampled as nonablated control. Hematoxylin and eosin (H&E) slides together with nicotinamide adenine dinucleotide (NADH) stained preparations were made. The NADH staining was quantified using computerized digital image recognition techniques.

RESULTS

Control sections (n = 20) demonstrated normal pancreatic architecture on H&E and strong NADH staining indicating preserved tissue oxidative metabolism. RF produced a temperature-dependent destruction of parenchymal architecture (H&E) with a corresponding loss of NADH activity. There was no evidence of thermal injury to the duodenum. Quantification of NADH staining demonstrated a median positive staining of 69.26% (55.87-97.28) for control tissue compared with 1.40% (0-7.77) for ablated pancreas (P < 0.001; Mann-Whitney U test).

CONCLUSION

This study describes the development of a relatively simple, reliable, and reproducible model for evaluation of RF ablation of pancreatic parenchyma.

Porcine liver: morphologic characteristics and cell viability at experimental radiofrequency ablation with internally cooled electrodes

PURPOSE

To evaluate morphologic characteristics and cell viability of radiofrequency ablation zones in porcine liver.

MATERIALS AND METHODS

Approval of the study protocol was obtained from the Ethics Committee on Use of Live Animals for Teaching and Research at University of Hong Kong. Internally cooled electrodes were used to produce 120 ablated zones ex vivo and 60 ablated zones in vivo with single electrodes (1-, 2-, and 3-cm exposed lengths) or clustered electrodes (1.0-, 2.0-, and 2.5-cm exposed lengths) at 4, 8, 12, and 16 minutes of ablation (ex vivo) and 8 and 12 minutes of ablation (in vivo). Morphologic measurements of each ablated zone were performed. Cell viability in each ablated zone was assessed qualitatively with histochemical staining and quantitatively with measurement of intracellular adenosine 5'-triphosphate (ATP) concentration.

RESULTS

Exposed length of electrode (coefficient = 0.79, standard error = 0.04, P < .001), duration of ablation (coefficient = 0.14, standard error = 0.01, P < .001), and clustered electrode design (coefficient = 1.21, standard error = 0.05, P < .001) were independent factors that affected minimal transverse diameter and volume of ablated zone in ex vivo study. Similar morphologic characteristics existed among ablated zones in in vivo study. Mean distance of ablation beyond the electrode tip remained constant (ex vivo, 1.0 cm +/- 0.08 [standard deviation]; in vivo, 0.5 cm +/- 0.05) regardless of different ablation conditions. Histochemical staining revealed no viable hepatocytes from center to margins of white zone in each ablated area. Mean intracellular ATP concentration in margins of white zone (9.5 x 10(-12) mol/microg DNA +/- 1.43) was lower than that in red zone (4088 x 10(-12) mol/microg DNA +/- 65.97, P < .001) and in adjacent normal liver (4528 x 10(-12) mol/microg DNA +/- 52.74, P < .001).

CONCLUSION

Distance of ablation beyond the tip of the electrode remained constant (ex vivo, 1.0 cm; in vivo, 0.5 cm) with different conditions of ablation. Complete and uniform cellular destruction was achieved in the white zone of ablated area.

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.