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

US-Guided Percutaneous Radiofrequency Ablation of Locally Advanced Pancreatic Adenocarcinoma: A 5-Year High-Volume Center Experience

PURPOSE

 The aim of this study was to investigate the safety and effectiveness of percutaneous radiofrequency ablation (RFA) in locally advanced pancreatic cancer (LAPC) of the pancreatic body by assessing the overall survival of patients and evaluating the effects of the procedure in the clinical and radiological follow-up.

MATERIALS AND METHODS

 Patients with unresectable LAPC after failed chemoradiotherapy for at least six months were retrospectively included. Percutaneous RFA was performed after a preliminary ultrasound (US) feasibility evaluation. Contrast-enhanced computed tomography (CT) and CA 19.9 sampling were performed before and 24 hours and 30 days after the procedure to evaluate the effects of the ablation. Patients were followed-up after discharge considering the two main endpoints: procedure-related complications and death.

RESULTS

 35 patients were included, 5 were excluded. All patients underwent RFA with no procedure-related complications reported. The mean size of tumors was 49 mm before treatment. The mean dimension of the ablated necrotic zone was 32 mm, with a mean extension of 65 % compared to the whole tumor size. Tumor density was statistically reduced one day after the procedure (p < 0.001). The mean CA 19.9 levels before and 24 hours and 30 days after the procedure were 285.8 U/mL, 635.2 U/mL, and 336.0 U/mL, respectively, with a decrease or stability at the 30-day evaluation in 80 % of cases. The mean survival was 310 (65-718) days.

CONCLUSION

 Percutaneous RFA of LAPC is a feasible technique in patients who cannot undergo surgery, with great debulking effects and a very low complication rate.

Effect of Portal Vein and Hepatic Artery Occlusion on Radiofrequency Ablation: Animal Experiment Comparing MR and Histology Measurements of the Ablation Zones

PURPOSE

This animal experimental study evaluated how hepatic artery and portal vein transient occlusion affects the ablation zone of hepatic radiofrequency ablation (RFA).

MATERIAL AND METHODS

Twenty-one rabbits were divided into three groups of seven each: (1) control, (2) hepatic artery occlusion, and (3) portal vein occlusion by a balloon catheter. For each rabbit, two or three RFA sessions were performed using an electrode needle. Ablation time, temperature around the tip of RFA needle at the end of RFA, ablation volume on fat-suppressed T1-weighted image in the hepatobiliary phase, and coagulative necrosis area on histopathology were measured and compared between the three groups using the Kruskal-Wallis paired Mann-Whitney U tests.

RESULTS

In 43 RFA sessions (group 1, 15; group 2, 14; group 3, 14), mean tissue temperature in group 3 (77.0 °C ± 7.7 °C) was significantly higher compared to groups 1 (59.2 °C ± 18.8 °C; P = 0.010) and 2 (67.5 °C ± 9.9 °C; P = 0.010). In addition, mean ablation volume and coagulative necrosis in group 3 (2.10 ± 1.37 mm³ and 0.86 ± 0.28 mm², respectively) were larger compared to groups 1 (0.84 ± 0.30 mm³; P < 0.001 and 0.55 ± 0.26 mm²; P = 0.020, respectively) and 2 (0.89 ± 0.59 mm³; P = 0.002 and 0.60 ± 0.22 mm²; P = 0.024, respectively).

CONCLUSION

Portal vein occlusion potentially boosts tissue temperature, ablation volume, and area of histopathologically proven coagulative necrosis during hepatic RFA in the non-cirrhotic liver.

Liver Transection with Precoagulation Therapy in Liver Cirrhosis: Effective Use of an Energy Device at Hepatectomy

Background

Hepatectomy for liver cirrhosis patients requires skillful surgical technique and careful attention because of the fibrotic parenchyma, elevated portal pressure, and impaired coagulation. This report evaluated short- and long-term outcomes for liver cirrhosis patients receiving precoagulation therapy on the parenchymal transection plane, compared with noncoagulation cases.

Methods

Seventy-three patients diagnosed with cirrhosis via postoperative pathological findings were selected after reviewing 887 hepatectomy patient files. They were divided into a precoagulation group (n = 20) and a noncoagulation group (n = 53). There were no significant differences in patient and tumor factors between 2 groups.

Results

The precoagulation group had significantly less blood loss compared with noncoagulation group [282 vs 563g (P &lt; 0.05)], shorter operative time [214 vs 276 min (P = 0.06)], and shorter postoperative hospital stays [14.5 vs 22.5 days (P = 0.12)]. The median recurrence free survival rates time in the pre-coagulation group (733 days) was significantly longer than that in the non-coagulation group (400 days) (P &lt; 0.05). Overall survival rates showed rates showed no difference between the 2 groups (P = 0.62).

Conclusions

Precoagulation therapy may be the a preferred treatment application for hepatectomy patients with severe liver fibrosis.

In vivo ultrasound thermal ablation control using echo decorrelation imaging in rabbit liver and VX2 tumor

The utility of echo decorrelation imaging feedback for real-time control of in vivo ultrasound thermal ablation was assessed in rabbit liver with VX2 tumor. High-intensity focused ultrasound (HIFU) and unfocused (bulk) ablation were performed using 5 MHz linear image-ablate arrays. Treatments comprised up to nine lower-power sonications, followed by up to nine higher-power sonications, ceasing when the average cumulative echo decorrelation within a control region of interest exceeded a predefined threshold (- 2.3, log10-scaled echo decorrelation per millisecond, corresponding to 90% specificity for tumor ablation prediction in previous in vivo experiments). This threshold was exceeded in all cases for both HIFU (N = 12) and bulk (N = 8) ablation. Controlled HIFU trials achieved a significantly higher average ablation rate compared to comparable ablation trials without image-based control, reported previously. Both controlled HIFU and bulk ablation trials required significantly less treatment time than these previous uncontrolled trials. Prediction of local liver and VX2 tumor ablation using echo decorrelation was tested using receiver operator characteristic curve analysis, showing prediction capability statistically equivalent to uncontrolled trials. Compared to uncontrolled trials, controlled trials resulted in smaller thermal ablation regions and higher contrast between echo decorrelation in treated vs. untreated regions. These results indicate that control using echo decorrelation imaging may reduce treatment duration and increase treatment reliability for in vivo thermal ablation.

Percutaneous cryoablation for the treatment of liver cancer at special sites: an assessment of efficacy and safety

Background

To assess the safety and efficacy of cryoablation (CA) devices for the treatment of liver cancer at special sites in a retrospective study.

Methods

Special site liver cancer was defined as the tumors directly abutting surrounding structures (such as the liver capsule, gallbladder, vessel, diaphragm, intestine, and adrenal gland) with a maximum distance of 1.0 cm between the tumor and these organs. Sixty-six patients (49 men, 17 women; mean age, 60.8 years; age range, 27-82 years) were included. CA procedure was performed to treat 69 tumors under the guidance of computed tomography or ultrasound. Local tumor progression was assessed during the follow-up. A visual analog scale (VAS) evaluated the pain degree. Complications were assessed during and after every procedure.

Results

The number of tumors under the liver capsule and adjacent to the gallbladder, portal or hepatic vein, diaphragm, intestine, and adrenal gland were 29, 5, 8, 14, 7, and 6, respectively. The median follow-up time was 14 months (range, 2-28 months). In the 69 procedures, the technical success rate was 100%. The cumulative local tumor progression rates at 6, 9, 15, and 24 months were 10.2%, 16.5%, 20.9%, and 30.5%, respectively. No cases of serious complications occurred. During operation, the occurrence rates of subcapsular hemorrhage and pneumothorax were 2.9% and 1.4%, respectively. After the operation, the occurrence rate of biloma, capsular injury, subcapsular planting metastasis, and pneumothorax were 1.4%, 18.8%, 1.4%, and 2.8%, respectively. The average score of 66 patients with a VAS was 2.15±0.63 during the operation.

Conclusions

Percutaneous CA is safe and effective for patients with special site liver cancer.

Experience and outcomes in living donor liver procurement using the water jet scalpel

BACKGROUND

The aim of the present study was to clarify treatment outcomes of living donor liver procurement using the water jet scalpel (WJS).

METHODS

This single-center, retrospective cohort study included 40 living donors who underwent liver procurement from January 2014 to December 2018. One living donor who underwent posterior segmentectomy was excluded. Clinical data and outcomes after surgery for 20 WJS donors and 19 Cavitron Ultrasonic Surgical Aspirator (CUSA) donors were compared.

RESULTS

Preoperative and excised graft data did not differ significantly between the WJS and CUSA groups. Operation time (P = 0.025) and parenchymal transection time (P = 0.007) were significantly shorter in the WJS group. There was no difference between the groups in terms of short-term outcomes after surgery. Multivariate analysis revealed that WJS offered significant advantages over CUSA in terms of shortening parenchymal transection time (P = 0.017).

CONCLUSION

Living donor liver procurement using WJS contributes to shortening of parenchymal transection time while maintaining the same level of safety as when using CUSA.

Real-Time Spatiotemporal Control of High-Intensity Focused Ultrasound Thermal Ablation Using Echo Decorrelation Imaging in ex Vivo Bovine Liver

The ability to control high-intensity focused ultrasound (HIFU) thermal ablation using echo decorrelation imaging feedback was evaluated in ex vivo bovine liver. Sonications were automatically ceased when the minimum cumulative echo decorrelation within the region of interest exceeded an ablation control threshold, determined from preliminary experiments as -2.7 (log-scaled decorrelation per millisecond), corresponding to 90% specificity for local ablation prediction. Controlled HIFU thermal ablation experiments were compared with uncontrolled experiments employing two, five or nine sonication cycles. Means and standard errors of the lesion width, area and depth, as well as receiver operating characteristic curves testing ablation prediction performance, were computed for each group. Controlled trials exhibited significantly smaller average lesion area, width and treatment time than five-cycle or nine-cycle uncontrolled trials and also had significantly greater prediction capability than two-cycle uncontrolled trials. These results suggest echo decorrelation imaging is an effective approach to real-time HIFU ablation control.

Percutaneous Radiofrequency Ablation of Unresectable Locally Advanced Pancreatic Cancer: Preliminary Results

AIM

The objective of this study was to evaluate the efficacy of percutaneous radiofrequency ablation of locally advanced pancreatic cancer located in the pancreatic body.

MATERIALS AND METHODS

Patients with biopsy-proven locally advanced pancreatic adenocarcinoma were considered for percutaneous radiofrequency ablation. Postprocedural computed tomography studies and Ca19.9 tumor marker evaluation were performed at 24 hours and 1 month. At computed tomography, treatment effect was evaluated by excluding the presence of complications. The technical success of the procedure is defined at computed tomography as the achievement of tumoral ablated area.

RESULTS

Twenty-three patients have been included in the study. Five of the 23 patients were excluded. At computed tomography, the mean size of the intralesional postablation necrotic area was 32 mm (range: 15-65 mm). Technical success of the procedure has been obtained in 16 (93%) of the 18 cases. None of the patients developed postprocedural complications. Mean Ca19.9 serum levels 1 day before, 1 day after, and 1 month after the procedure were 285.8 U/mL (range: 16.6-942.0 U/mL), 635.2 U/mL (range: 17.9-3368.0 U/mL), and 336.0 U/mL (range: 7.0-1400.0 U/mL), respectively. Follow-up duration was less than 6 months for 11 patients and more than 6 months for 7 patients. At the time of the draft of this article, the mean survival of the patients included in the study was 185 days (range: 62-398 days).

CONCLUSION

Percutaneous radiofrequency ablation of locally advanced adenocarcinoma has a high technical success rate and is effective in cytoreduction both at imaging and laboratory controls.

Percutaneous ablation of pancreatic cancer

Pancreatic ductal adenocarcinoma is a highly aggressive tumor with an overall 5-year survival rate of less than 5%. Prognosis and treatment depend on whether the tumor is resectable or not, which mostly depends on how quickly the diagnosis is made. Chemotherapy and radiotherapy can be both used in cases of non-resectable pancreatic cancer. In cases of pancreatic neoplasm that is locally advanced, non-resectable, but non-metastatic, it is possible to apply percutaneous treatments that are able to induce tumor cytoreduction. The aim of this article will be to describe the multiple currently available treatment techniques (radiofrequency ablation, microwave ablation, cryoablation, and irreversible electroporation), their results, and their possible complications, with the aid of a literature review.

Safety and Efficacy of Transarterial Chemoembolization Combined with CT-Guided Radiofrequency Ablation for Hepatocellular Carcinoma Adjacent to the Hepatic Hilum within Milan Criteria

PURPOSE

To retrospectively evaluate safety and efficacy of conventional transarterial chemoembolization with ethiodized oil (Lipiodol) combined with CT-guided radiofrequency (RF) ablation for hepatocellular carcinoma (HCC) adjacent to the hepatic hilum.

MATERIALS AND METHODS

Between January 2007 and December 2010, conventional transarterial chemoembolization combined with CT-guided RF ablation was performed in 40 patients with HCC adjacent to the hepatic hilum within Milan criteria (group A). Major complications, complete tumor ablation rate, local tumor progression rate, and overall survival were compared with 107 patients with HCC nonadjacent to the hepatic hilum (group B) treated by conventional transarterial chemoembolization combined with CT-guided RF ablation during the same period.

RESULTS

Major complications included one case of large hepatic artery-portal vein fistula in group A (2.5%; 1/40) and one case of acute portal vein thrombosis, left heart failure, and tumor seeding in group B (2.8%; 3/107); the difference was not significant between the two groups (P = 1.000). There were no significant differences between the two groups in complete tumor ablation rate (80.0% vs 86.0%; P = .374), local tumor progression rates (1-year, 12.5% vs 14.1%; 2-year, 28.2% vs 24.2%; 3-year, 32.0% vs 27.6%; P = .723), and overall survival (1-year, 92.3% vs 91.8%; 3-year, 79.1% vs 79.3%; 5-year, 59.5% vs 58.4%; P = .555).

CONCLUSIONS

Conventional transarterial chemoembolization combined with CT-guided RF ablation was safe and effective in selected patients with HCC adjacent to the hepatic hilum within Milan criteria.

Liver resection for hepatocellular carcinoma using a microwave tissue coagulator: Experience of 1118 cases

AIM: To present our extensive experience of hepatectomy for hepatocellular carcinoma using a microwave tissue coagulator to demonstrate the effectiveness of this device.

METHODS: A total of 1118 cases (1990-2013) were reviewed, with an emphasis on intraoperative blood loss, postoperative bile leakage and fluid/abscess formation, and adaptability to anatomical resection and hepatectomy with hilar dissection.

RESULTS: The median intraoperative blood loss was 250 mL; postoperative bile leakage and fluid/abscess formation were seen in 3.0% and 3.3% of cases, respectively. Anatomical resection was performed in 275 cases, including 103 cases of hilar dissection that required application of microwave coagulation near the hepatic hilum. There was no clinically relevant biliary tract stricture or any vascular problems due to heat injury. Regarding the influence of cirrhosis on intraoperative blood loss, no significant difference was seen between cirrhotic and non-cirrhotic patients (P = 0.38), although cirrhotic patients tended to have smaller tumors and underwent less invasive operations.

CONCLUSION: This study demonstrated outcomes of an extensive experience of hepatectomy using heat coagulative necrosis by microwave tissue coagulator.

Complications of image-guided thermal ablation of liver and kidney neoplasms

Image-guided thermal ablation is a widely accepted tool in the treatment of a variety of solid organ neoplasms. Among the different techniques of ablation, radiofrequency ablation, cryoablation, and microwave ablation have been most commonly used and investigated in the treatment of liver and kidney neoplasms. This article will review complications following thermal ablation of tumors in the liver and kidney, and discuss the risks and clinical presentation of each complication as well as how to treat and potentially avoid complications.

MAFR. Complications of radiofrequency ablation of hepatic tumors: Frequency and risk factors

Radiofrequency ablation (RFA) has become an important option in the therapy of primary and secondary hepatic tumors. Surgical resection is still the best treatment option, but only a few of these patients are candidates for surgery: multilobar disease, insufficient liver reserve that will lead to liver failure after resection, extra-hepatic disease, proximity to major bile ducts and vessels, and co-morbidities. RFA has a low mortality and morbidity rate and is considered to be safe. Thus, complications occur and vary widely in the literature. Complications are caused by thermal damage, direct needle injury, infection and the patient’s co-morbidities. Tumor type, type of approach, number of lesions, tumor localization, underlying hepatic disease, the physician’s experience, associated hepatic resection and lesion size have been described as factors significantly associated with complications. The physician in charge should promptly recognize high-risk patients more susceptible to complications, perform a close post procedure follow-up and manage them early and adequately if they occur. We aim to describe complications from RFA of hepatic tumors and their risk factors, as well as a few techniques to avoid them. This way, others can decrease their morbidity rates with better outcomes.

Comparison of internally cooled wet electrode and hepatic vascular inflow occlusion method for hepatic radiofrequency ablation

Background/Aims

Various strategies to expand the ablation zone have been attempted using hepatic radiofrequency ablation (RFA). The optimal strategy, however, is unknown. We compared hepatic RFA with an internally cooled wet (ICW) electrode and vascular inflow occlusion.

Methods

Eight dogs were assigned to one of three groups: only RFA using an internally cooled electrode (group A), RFA using an ICW electrode (group B), and RFA using an internally cooled electrode with the Pringle maneuver (group C). The ablation zone diameters were measured on the gross specimens, and the volume of the ablation zone was calculated.

Results

The ablation zone volume was greatest in group B (1.82±1.23 cm³), followed by group C (1.22±0.47 cm³), and then group A (0.48±0.33 cm³). The volumes for group B were significantly larger than the volumes for group A (p=0.030). There was no significant difference in the volumes between groups A and C (p=0.079) and between groups B and C (p=0.827).

Conclusions

Both the usage of an ICW electrode and hepatic vascular occlusion effectively expanded the ablation zone. The use of an ICW electrode induced a larger ablation zone with easy handling compared with using hepatic vascular occlusion, although this difference was not statistically significant.

Venous thrombosis after radiofrequency ablation for hepatocellular carcinoma

OBJECTIVE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

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

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

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

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

Imaging to optimize liver tumor ablation

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

Radiofrequency ablation of locally advanced pancreatic adenocarcinoma: an overview

Radiofrequency ablation (RFA) of pancreatic neoplasms is restricted to locally advanced, non-resectable but non-metastatic tumors. RFA of pancreatic tumors is nowadays an ultrasound-guided procedure performed during laparotomy in open surgery. Intraoperative ultrasound covers the mandatory role of staging, evaluation of feasibility, guidance and monitoring of the procedure. Different types of needle can be used. The first aim in the evaluation of RFA as a treatment for locally advanced pancreatic ductal adenocarcinoma, in order of evaluation but not of importance, is to determine the feasibility of the procedure. The second aim is to establish the effect of RFA on tumoral mass in terms of necrosis and cytoreduction. The most important aim, third in order of evaluation, is the potential improvement of quality of life and survival rate. Nowadays, only a few studies assess the feasibility of the procedure. The present paper is an overview of RFA for pancreatic adenocarcinoma.

High-intensity focused ultrasound (HIFU): effective and safe therapy for hepatocellular carcinoma adjacent to major hepatic veins

Hepatocellular carcinoma (HCC) is an especially frequent malignancy in China. Radiofrequency ablation, percutaneous ethanol injection, transarterial chemoembolization, cryoablation, microwave coagulation, and laser-induced interstitial thermotherapy all offer potential local tumor control and occasionally achieve long-term disease-free survival. High-intensity focused ultrasound (HIFU), as a noninvasive therapy, can be applied to treat tumors that are difficult to treat with other techniques. The preliminary results of HIFU in clinical studies are encouraging. The aims of this investigation were to assess the efficacy of the system in obtaining necrosis of the target tissue and to determine whether HIFU ablation is hazardous to adjacent major blood vessels. Over 7 years, thirty-nine patients with HCC were enrolled in this investigation. The inferior vena cava (IVC), main hepatic vein branches, and the portal vein and its main branches were evaluated. The distance between tumor and main blood vessel was less than 1 cm in all these enrolled patients. Contrast-enhanced MRI was used to evaluate the perfusion of tumors and major blood vessels. We conducted HIFU ablation for the treatment of 39 patients with 42 tumors, with each tumor measuring 7.4+/-4.3 (1.5-22) cm in its greatest dimension. Among the 39 patients, 23 were males and 16 females. The average age was 53.2 years (range 25-77 years). Thirty-seven patients had a solitary lesion, one had two lesions, and the remaining one had three lesions. Nineteen lesions were located in the right lobe of liver, 18 in the left lobe, and 5 in both right and left lobes. Among the 42 tumors, 25 were adjacent to 1 blood vessel, 12 adjacent to 2 main vessels, 2 adjacent to 3 main vessels, and 1 adjacent to 4 main vessels. Twenty-one of the 42 tumors were completely ablated, while the rest of the tumors were ablated by more than 50% of lesion volume after one session of HIFU. No major blood vessel injury was observed in any subject after 23.8+/-17.2 months follow-up. HIFU can achieve complete tumor necrosis even when the lesion is located adjacent to the major hepatic blood vessels. Short-term and long-term follow-up results show that HIFU can be safely used to ablate the tumors adjacent to major vessels.

Influence of approach on outcome in radiofrequency ablation of liver tumors

In this article some recent data concerning the approach on radiofrequency ablation (RFA) of liver tumors are reviewed. Specifically, several critical statements between surgical and percutaneous approach are raised and discussed: (1) Open approach may lead to a higher complication rate; (2) Temporary occlusion of hepatic inflow during surgical approach may lead to a higher rate of ablation of the liver tumors; (3) Surgical approach may permit better targeting of the tumor to be ablated. (4) Surgical approach may discover additional liver tumors. Finally, several conclusions and recommendations are also addressed.

Temporary liver blood-outflow occlusion increases effectiveness of radiofrequency ablation: An experimental study on pigs

AIM

To evaluate the feasibility of liver blood outflow (LBOF) occlusion and its impact on the effectiveness of radiofrequency ablation (RFA).

METHODS

The experiment was performed on 10 pigs. The animals were divided into groups A and B according to RFA protocol. In group A (n=5) the RFA time was that taken to reach the target temperature of 105 degrees C, whereas group B (n=5) had a constant RFA temperature of 105 degrees C and constant time of 8min. The liver blood flow (LBF) was quantified using Doppler ultrasonography before LBOF occlusion and after that. RFA were performed using an expandable 3cm RF needle. Two liver ablations created in different liver lobes were compared; the first ablation was created before balloon inflation and the second one was created under LBOF occlusion. The time required for RFA procedure, liver ablation volumes, shape and microscopic changes of the thermoablated zones were recorded.

RESULTS

The LBF dropped significantly in all liver vessels after balloon inflation. The volume of the ablated area was 8.2+/-2.2cm(3) and increased significantly after LBOF occlusion to 17.4+/-3.8cm(3) (p<0.001), in group A. A significant enlargement of the ablated area with occluded LBF was registered in group B, it was 6.7+/-2.8cm(3) versus 19.4+/-1.8cm(3) respectively (p<0.01).

CONCLUSIONS

Temporary LBOF occlusion led to a significant reduction in liver blood flow, enlargement of the thermoablated area volume and homogeneity of the coagulated zones.

Incomplete ablation after radiofrequency ablation of hepatocellular carcinoma: analysis of risk factors and prognostic factors

BACKGROUND

Complete ablation rates after a single session of radiofrequency ablation (RFA) of hepatocellular carcinoma (HCC) vary from 48% to 97%. Limited data are available regarding risk factors and prognostic significance of incomplete ablation.

METHODS

Between April 2001 and March 2006, 298 patients underwent RFA of 393 HCC nodules with an intent of complete ablation after a single session. Risk factors for incomplete ablation and its effect on overall survival were analyzed.

RESULTS

Two hundred seventy-three (91.6%) underwent complete tumor ablation, whereas the other 25 (8.4%) underwent incomplete tumor ablation after a single session of RFA. By multivariate analysis, tumor size > 3 cm (P = .049) was found to be the only independent risk factor for incomplete ablation. There was no statistically significant difference in overall survival between patients with complete and incomplete ablation. By univariate analysis, no previous transarterial chemoembolization (TACE), preoperative serum alfa-fetoprotein < or = 100 microg/mL, and complete response after further treatment of incomplete ablation were associated with better overall survival in patients with incomplete ablation.

CONCLUSIONS

This study demonstrated that incomplete ablation after RFA of HCC was associated with tumor size > 3 cm. Our data also suggest that aggressive further treatment of tumors with incomplete ablation aiming at complete tumor response improves overall survival.

Radiofrequency Ablation of Hepatocellular Carcinoma: Correlation Between Local Tumor Progression After Ablation and Ablative Margin

OBJECTIVE

To identify the determinants of tumor progression, we examined the ablation zones and patterns of local progression of small single primary hepatocellular carcinomas after radiofrequency ablation.

MATERIALS AND METHODS

Eighty-five patients with single primary hepatocellular carcinoma less than 3 cm in diameter underwent complete tumor ablation. Clinical and biochemical features, tumor characteristics, tumor location within 5 mm from intrahepatic vessels, needle biopsy before treatment, and presence of ablative margin of 5 mm or more were statistically analyzed as determinants of local tumor progression. The Kaplan-Meier method and a Cox model were used for the analyses. Patterns of local tumor progression were examined by image analysis.

RESULTS

During a median observation period of 30.3 months, 14 (16.5%) of the 85 patients had local tumor progression. The results of the log-rank test showed that the presence of vessels contiguous with the tumor (p = 0.0292) and the absence of an ablative margin of at least 5 mm (p = 0.019) significantly correlated with local tumor progression. Cox regression analysis showed that the absence of an ablative margin of at least 5 mm was an independent factor (p = 0.04). The most common pattern of local tumor progression was a single viable outgrowth from the side of the ablated area when the ablative margin was less than 5 mm. Multiple viable outgrowths were observed in one case despite the presence of an ablative margin greater than 5 mm.

CONCLUSION

An ablation zone with an ablative margin of 5 mm or greater was the most important factor for local control of hepatocellular carcinoma.

A novel approach to brachytherapy in hepatocellular carcinoma using a phosphorous32 (32P) brachytherapy delivery device--a first-in-man study

PURPOSE

While potentially very useful, percutaneously delivered brachytherapy of inoperable intra-abdominal solid tumors faces significant technical challenges. This first-in-man study is designed to determine the safety profile and therapeutic efficacy of a novel phosphorous (32P) brachytherapy device (BrachySil) in patients with unresectable hepatocellular carcinoma.

METHODS AND MATERIALS

Patients received single percutaneous and transperitoneal implantations of BrachySil under local anesthesia directly into liver tumors under ultrasound or computed tomographic guidance, at an activity level of 4 MBq/cc of tumor. Toxicity was assessed by the nature, incidence, and severity of adverse events (Common Toxicity Criteria scores) and by hematology and clinical chemistry parameters. Target tumor response was assessed with computed tomographic scans at 12 and 24 weeks postimplantation using World Health Organization criteria.

RESULTS

Implantations were successfully carried out in 8 patients (13-74 MBq, mean 40 MBq per tumor) awake and under local anesthesia. Six of the 8 patients reported 19 adverse events, but no serious events were attributable to the study device. Changes in hematology and clinical chemistry were similarly minimal and reflected progressive underlying hepatic disease. All targeted tumors were responding at 12 weeks, with complete response (100% regression) in three lesions. At the end of the study, there were two complete responses, two partial responses, three stable diseases, and one progressive disease.

CONCLUSION

Percutaneous implantation of this novel 32P brachytherapy device into hepatocellular carcinoma is safe and well tolerated. A significant degree of antitumor efficacy was demonstrated at this low dose that warrants further investigation.

Kinetics of indocyanine green removal from blood can be used to predict the size of the area removed by radiofrequency ablation of hepatic nodules

BACKGROUND AND AIM

The size of radiofrequency ablation (RFA) in the liver can be negatively influenced by the surrounding blood flow. The indocyanine green (ICG) test can be used to evaluate the effective blood flow in the liver, and distance from the hilus can affect local blood flow. The aim of this study was to assess whether the ICG test or distance from the hilus could be used to predict the size of the ablated area in liver by RFA treatment of hepatocellular carcinoma (HCC) nodules.

METHODS

The RFA measurements of 44 HCC nodules in 39 patients were retrospectively studied. Cases were included if they met the following criteria: (i) no catheter treatment before RFA; (ii) no movement of the RFA device; (iii) strict ablation time; and (iv) only one ablation. In all patients, ICG-R15 testing was done immediately before RFA and the initial therapeutic efficacy was evaluated by dynamic computed tomography scanning 2-5 days after RFA. The correlation between the maximum size of the RFA area and the ICG test results or the distance of the target area from the hilus (site of first portal vein divergence) were analyzed statistically.

RESULTS

The ICG-R15 result was significantly correlated with the maximum diameter of the ablated area both in 2 cm-electrode tip length (R2 = 0.35, P = 0.0012), and in 3 cm-tip length (R2 = 0.26, P = 0.0377). Multiple-regression analysis showed that the electrode tip length (P = 0.0010) and ICG-R15 (P = 0.0046) were independent factors that could predict the maximum diameter of the RFA area.

CONCLUSION

The results of ICG testing can be used to predict the size of the area that will be ablated at a target liver site before RFA treatment.

Experimental Radiofrequency Ablation Near the Portal and the Hepatic Veins in Pigs: Differences in Efficacy of a Monopolar Ablation System

BACKGROUND

We sought to compare the efficacy of a monopolar radiofrequency ablation system in vivo near the portal vein and the hepatic veins in porcine liver.

MATERIALS AND METHODS

Radiofrequency ablation of healthy livers near the portal vein and the hepatic veins was performed in 10 pigs with a multitined expandable electrode. Volumes and diameters of zones of ablation were assessed by magnetic resonance imaging.

RESULTS

Volumes (16.0 +/- 5.5 mL, P = 0.001) and diameters (4.0 +/- 0.7 cm, 3.3 +/- 0.7 cm, 3.0 +/- 0.6 cm, P <or= 0.05) of the zones of ablation near the hepatic veins were larger than that near the portal vein (7.5 +/- 4.1 mL, 3.2 +/- 0.7 cm, 2.6 +/- 0.7 cm, 2.4 +/- 0.6 cm). Energy deposition needed to ablate liver tissue was higher (P = 0.003) for radiofrequency ablation near the portal vein (3.16 +/- 1.58 kJ/mL) than for radiofrequency ablation near the hepatic veins (1.65 +/- 1.14 kJ/mL).

CONCLUSIONS

Higher energy deposition is needed to ablate liver tissue near the portal vein than near the hepatic veins. As a result, the zone of ablation is larger near the hepatic vein than near the portal vein.

Efficacy and safety of radiofrequency ablation for perivascular hepatocellular carcinoma without hepatic inflow occlusion

BACKGROUND

The role of radiofrequency ablation (RFA) for perivascular (up to 5 mm from the major intrahepatic portal vein or hepatic vein branches) hepatocellular carcinoma (HCC) is unclear because of possible incomplete tumour ablation and potential vascular damage. This study aimed to evaluate the safety and efficacy of RFA for perivascular HCC without hepatic inflow occlusion.

METHODS

Between May 2001 and November 2003, RFA using an internally cooled electrode was performed on 52 patients with perivascular HCC (group 1) through open (n = 39), percutaneous (n = 9), laparoscopic (n = 2) and thoracoscopic (n = 2) approaches. Hepatic inflow occlusion was not applied during the ablation procedure. The perioperative and postoperative outcomes were compared with those of 90 patients with non-perivascular HCC (group 2) treated by RFA during the same period.

RESULTS

The morbidity rate was similar between groups 1 and 2 (25 versus 28 per cent; P = 0.844). One patient in group 1 (2 per cent) and two in group 2 (2 per cent) had developed thrombosis of major intrahepatic blood vessels on follow-up computed tomography scan. There were no significant differences between groups 1 and 2 in mortality rate (2 versus 0 per cent; P = 0.366), complete ablation rate for small HCC (92 versus 98 per cent; P = 0.197), local recurrence rate (11 versus 9 per cent; P = 0.762) and overall survival (1-year: 86 versus 87 per cent; 2-year: 75 versus 75 per cent; P = 0.741).

CONCLUSION

RFA without hepatic inflow occlusion is a safe and effective treatment for perivascular HCC.

Complications of percutaneous radiofrequency ablation for hepato-cellular carcinoma: imaging spectrum and management

Percutaneous radiofrequency (RF) ablation is feasible for the treatment of unresectable hepatocellular carcinoma, and experience at the authors' institution during 5 years indicates that percutaneous RF ablation can be performed safely in most cases. However, early or late complications related to mechanical or thermal damage may be observed at follow-up examination. Complications may be classified in three groups: vascular (eg, portal vein thrombosis, hepatic vein thrombosis with partial hepatic congestion, hepatic infarction, and subcapsular hematoma), biliary (eg, bile duct stenosis and biloma, abscess, and hemobilia), and extrahepatic (eg, injury to the gastrointestinal tract, injury to the gallbladder, pneumothorax and hemothorax, and tumor seeding). Most complications can be managed with conservative treatment, percutaneous or endoscopic drainage, or surgical repair. Because an early and accurate diagnosis is necessary for proper management, radiologists should be familiar with the imaging features of each type of complication.

Experimental hepatic radiofrequency ablation using wet electrodes: electrode-to-vessel distance is a significant predictor for delayed portal vein thrombosis

The aim of this study was to examine possible explanatory variables associated with acute and delayed portal vein thrombosis after hepatic radiofrequency (RF) ablation using wet electrodes. Coagulations were created within 1.5 cm of the right portal vein (RPV) branch in 12 pigs with (n = 6) or without (n = 6) Pringle manoeuvre. Sham operations with Pringle manoeuvre were performed in four animals. Rotational portal venography was performed prior to ablation, 10 min after ablation and 4 days after ablation. Vessel diameters and vessel patency was determined from the portal venograms. Distance between the ablation electrode and RPV was measured from 3-dimensional reconstructions of the portal venograms. The portal veins were examined by microscopy. Delayed portal vein thrombosis was found in two of six animals in the Pringle group and three of six animals in the control group 4 days after ablation (P = 1.0, Fisher's exact test). All five occurrences of delayed portal vein thrombosis were found in the six animals with a distance between the ablation electrode and RPV of 5 mm or less (P = 0.030), indicating that the electrode-to-vessel distance may be an independent explanatory factor for delayed portal vein thrombosis after RF ablation with wet electrodes.

High operative risk of cool-tip radiofrequency ablation for unresectable pancreatic head cancer

BACKGROUND AND OBJECTIVES

To report and discuss the effect, complications and mortality of cool-tip radiofrequency ablation (RFA) for unresectable pancreatic cancer.

METHODS

During October 2003 to July 2004, sixteen patients with unresectable pancreatic cancer were treated by open cool-tip RFA. One-half of the 16 patients had tumors located in the pancreatic head. A 5-mm minimum safe distance between RFA site and major peripancreatic vessels was kept to avoid injury to the vessels.

RESULTS

Six of twelve patients with back pain got pain relief postoperatively. Pancreatic fistula occurred in three patients (18.8%) and healed smoothly in 7-10 days with routine abdominal drainage. The mortality was 25% (4/16). In the four death cases, tumors were all located in the pancreatic head; three patients with tumor close to portal vein died suddenly of massive gastrointestinal hemorrhage on the 4th, 30th, 40th postoperative day respectively and a 79-year-old patient died of acute renal failure on the 2nd postoperative day.

CONCLUSIONS

Standard use of cool-tip RFA was dangerous for pancreatic head cancer close to portal vein, in which a 5-mm minimum safe distance between RFA site and major peripancreatic vessels might not be enough to avoid injury to the vessels.

IMPACT OF BLOOD FLOW OCCLUSION ON LIVER NECROSIS FOLLOWING THERMAL ABLATION

BACKGROUND

Laser, radiofrequency and microwave are common techniques for local destruction of liver tumours by thermal ablation. The main limitation of thermal ablation treatment is the volume of necrosis that can be achieved. Blood flow occlusion is commonly advocated as an adjunct to thermal ablation to increase the volume of tissue necrosis based on macroscopic and histological assessment of immediate or direct thermal injury. This study examines the impact of blood flow occlusion on direct and indirect laser induced thermal liver injury in a murine model using histochemical methods to assess tissue vitality.

METHODS

Thermal ablation produced by neodymium yttrium-aluminium-garnet laser (wavelength 1064 nm) was applied to the liver of inbred male CBA strain mice at 2 W for 50 s (100 J). Treatment was performed with and without temporary portal vein and hepatic artery blood flow occlusion. Animals were killed upon completion of the procedure to assess direct thermal injury or at 24, 48 and 72 h to assess the progression of tissue damage. The maximum diameter of necrosis was assessed by vital staining for nicotinamide adenine dinucleotide (NADH) diaphorase. Microvascular changes were assessed by laser Doppler flowmetry, confocal in vivo microscopy and scanning electron microscopy.

RESULTS

The direct thermal injury (mean SE) assessed by NADH diaphorase staining was significantly greater following thermal ablation treatment without blood flow occlusion than with blood flow occlusion (3.3 (0.4) mm vs 2.9 (0.3) mm; P = 0.005). Tissue disruption, cracking and vacuolization was more pronounced adjacent to the fibre insertion site in the group treated with thermal ablation combined with blood flow occlusion. There was an equivalent increase in the extent of injury following therapy in both groups that reached a peak at 48 h. The maximum diameter of necrosis in the thermal ablation alone group at 48 h was significantly greater than the thermal ablation combined with blood flow occlusion group (5.8 (0.4) mm vs 5.3 (0.3) mm; P = 0.011). The patterns of microvascular injury were similar in both groups, varying in extent.

CONCLUSION

Temporary blood flow inflow occlusion appears to decrease the extent of initial injury measured by vital staining techniques and does not alter the time sequence of progressive tissue injury following thermal ablation therapy.

Evaluation of liver parenchymal pressure and portal endothelium damage during radio frequency ablation in an in vivo porcine model

BACKGROUND/AIMS

We previously developed a multi-step, incremental expansion method (multi-step method) for radio frequency ablation (RFA) in vitro, which prevented increases in pressure and reduced the ablation time as compared with other methods. In this study, we evaluated liver parenchymal pressure and portal endothelium damage during RFA with different devices and protocols in an in vivo porcine model.

METHOD

Nine healthy female pigs were anaesthetized. RFA was performed with two different devices and protocols; one involved the use of a LeVeen needle with a single-step full expansion method or a multi-step method, and the other used a cool-tip needle with 40 or 60 W power. We measured the pressure in the liver parenchyma and the gallbladder during RFA. We also evaluated portal endothelium damage by NADH staining.

RESULTS

The multi-step method with the LeVeen electrode resulted in the lowest parenchymal and intra-gallbladder pressures (multi-step method<single-step method <cool-tip 40 W <cool-tip 60 W). In contrast, the ablation time was shortest with the cool-tip needle at 60 W (cool-tip 60 W <cool-tip 40 W=multi-step method <single-step method). NADH staining revealed severe endothelium damage after ablation with the cool-tip needle, but only slight damage with the LeVeen needle.

CONCLUSION

Ablation with the LeVeen needle, especially when used with a multi-step protocol, produced less of an increase in liver parenchymal and intra-gallbladder pressures and less damage to portal endothelial cells than did the cool-tip electrode.

Precoagulation minimizes blood loss during standardized hepatic resection in an experimental model

BACKGROUND

Precoagulation of liver tissue before transection is a novel concept in hepatic surgery. Comparative data with conventional techniques are lacking. This study tested the hypothesis that precoagulation results in reduced blood loss during hepatic transection.

METHODS

Precoagulation was performed with two different devices, the TissueLink floating ball (group 1) and a dissecting sealer (group 2), and compared with ultrasonic dissection (group 3). For each technique 12 partial liver resections were performed in six pigs. Blood loss per dissection surface area was the main outcome parameter.

RESULTS

The transected surface area was similar in all groups. Animals in groups 1 and 2 had significantly less blood loss than those in group 3 (3.6 and 1.3 versus 11.9 ml/cm2 respectively; P = 0.009 and P = 0.002). One pig in group 1 died as a result of wound dehiscence. In one animal in group 2 a gastric perforation was observed after death. In group 3 bile leakage occurred in two animals, and a large haematoma was observed on the transection surface in one animal after death.

CONCLUSION

Precoagulation of liver tissue before transection is associated with less blood loss compared with ultrasonic dissection.

Mechanisms of Focal Heat Destruction of Liver Tumors

BACKGROUND

Focal heat destruction has emerged as an effective treatment strategy in selected patients with malignant liver tumors. Radiofrequency ablation, interstitial laser thermotherapy, and microwave treatment are currently the most widely applied thermal ablative techniques. A major limitation of these therapies is incomplete tumor destruction and overall high recurrences. An understanding of the mechanisms of tissue injury induced by focal hyperthermia is essential to ensure more complete tumor destruction. Here, the currently available scientific literature concerning the underlying mechanisms involved in the destruction of liver tumors by focal hyperthermia is reviewed.

METHODS

Medline was searched from 1960 to 2004 for literature regarding the use of focal hyperthermia for the treatment of liver tumors. All relevant literature was searched for further references.

RESULTS

Experimental evidence suggests that focal hyperthermic injury occurs in two distinct phases. The first phase results in direct heat injury that is determined by the total thermal energy applied, tumor biology, and the tumor microenvironment. Tumors are more susceptible to heat injury than normal cells as the result of specific biological features, reduced heat dissipating ability, and lower interstitial pH. The second phase of hyperthermic injury is indirect tissue damage that produces a progression of tissue injury after the cessation of the initial heat stimulus. This progressive injury may involve a balance of several factors, including apoptosis, microvascular damage, ischemia-reperfusion injury, Kupffer cell activation, altered cytokine expression, and alterations in the immune response. Blood flow modulation and administration of thermosensitizing agents are two methods currently used to increase the extent of direct thermal injury. The processes involved in the progression of thermal injury and therapies that may potentially modulate them remain poorly understood.

CONCLUSION

Focal hyperthermia for the treatment of liver tumors involves complex mechanisms. Evidence suggests that focal hyperthermia produces both direct and indirect tissue injury by differing underlying processes. Methods to enhance the effects of treatment to achieve complete tumor destruction should focus on manipulating these processes.

Experimental bile duct protection by intraductal cooling during radiofrequency ablation

BACKGROUND

The use of radiofrequency ablation (RFA) for liver tumours is limited by the proximity of large bile ducts to the targeted lesion. The aim of this randomized study was to evaluate intraductal cooling as a mean of protecting the bile ducts during RFA.

METHODS

Twelve pigs underwent RFA adjacent to the right bile duct. After placement of an intraductal cooling catheter and a RFA probe, pigs were randomized to cooling or no cooling. Intraductal temperature was measured in all animals. The bile ducts were assessed by magnetic resonance imaging (MRI) and cholangiography 1 and 28 days after the procedure.

RESULTS

Intraductal cooling abolished the increase of intraductal temperature seen in the absence of cooling. Concurrent cholangiography and MRI showed a biliary lesion in one of six pigs subjected to intraductal cooling and in five of six without cooling (P = 0.040). The biliary injuries were barely visible by MRI on day 1 but were clearly visible on day 28.

CONCLUSION

Intraductal cooling can prevent biliary injury induced by RFA. The exact parameters for intraductal cooling require further investigation to establish the best compromise between bile duct protection and complete ablation of surrounding tissue.

Radiofrequency ablation for malignant liver tumor

Radiofrequency ablation (RFA) has been widely practiced to treat unresectable malignant liver tumors. It has the merits of localized tumor ablation and preservation of maximal normal liver parenchyma. In recent years, there has been a tremendous expansion in the application of RFA for patients with malignant liver tumors. However, the therapeutic effect of this local ablation treatment needs to be balanced against its risks and possible local failure. This review focuses on the current status of RFA for malignant liver tumors, with special attention to the indication, approaches, complications, survival benefits, combination therapies, and comparison with other treatment modalities. Although the results of most clinical studies of RFA seem favorable, the associated risks and tumor recurrence should not be underestimated. Careful patient selection, meticulous RFA techniques, and prompt treatment of residual and recurrent tumors are necessary to ensure a better outcome after RFA. Until recently, there has been no strong evidence showing that RFA can replace any other treatment modalities in the management of liver tumors. Nonetheless, more convincing evidence by randomized trials is required for the establishment of a treatment protocol of RFA for patients with malignant liver tumors.

Selective portal vein clamping for radiofrequency ablation of hepatocellular carcinoma with portal vein invasion

Surgical resection provides potential cure for patients with hepatocellular carcinoma. Unfortunately, resection is suitable in only about 10-37% of patients because of the limited hepatic functional reserve from the underlying chronic liver disease in the majority of patients. Survival of patients with unresectable diseases, especially those with portal vein tumor invasion, remains very poor. Radiofrequency ablation (RFA) is a form of locoregional therapy that allows a selected group of previously inoperable patients to be treated. However, problems with RFA leading to induced portal vein thrombosis have been reported in the literature. Nevertheless, patients with portal vein tumor invasion may be considered for radiofrequency tumor ablation to improve survival. We report the case of a patient with hepatocellular carcinoma with left portal vein invasion. Complete tumor ablation was achieved after RFA with left portal vein clamping. He remained disease free both radiologically and biochemically 6 months after the operation.

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.

Progressive microvascular injury in liver and colorectal liver metastases following laser induced focal hyperthermia therapy

BACKGROUND AND OBJECTIVES

Focal hyperthermia by laser or radiofrequency is currently the preferred method for local ablation of liver tumors. The underlying mechanism of action of focal hyperthermia, in particular the relationship between the microvascular and tissue effect is uncertain and was investigated in a murine model.

STUDY DESIGN/MATERIALS AND METHODS

Focal hyperthermia produced by a Neodymium-Yttrium-Aluminium-Garnet laser (wavelength 1,064 nm) was applied to the normal liver and colorectal cancer liver metastases in inbred male CBA strain mice at 2 W for 50 seconds (100 J). Tissue injury was assessed at 0, 24, 48, 72, 120, and 168 hours following therapy by measurements of necrosis in tissue sections stained for nicotinamide adenine dinucleotide (NADH) diaphorase activity. Characteristics of microvascular injury were assessed at the various time points by scanning electron microscopy (SEM) of vascular resin casts, Laser Doppler flowmetry, and confocal in vivo microscopy.

RESULTS

Focal hyperthermia produced progressive tissue and vascular injury. There was an initial reduction in blood flow and increased vascular permeability in the microcirculation of both tumor and liver tissue immediately following heat application as assessed by laser Doppler flowmetry and confocal in vivo microscopy, respectively. SEM of vascular casts showed heterogeneous regions of microvascular injury immediately following heat application. The extent of initial vascular disruption or occlusion on SEM of vascular resin casts (mean+/-SE) was significantly less than the tissue necrosis in liver (1.9+/-0.1 mm vs. 3.0 mm+/-0.2 mm P<0.001), but was equivalent to the tissue injury in tumor tissue (3.5 mm+/-0.2 mm vs. 3.6 mm+/-0.1 mm P = 0.907). This was followed by a progressive increase in both microvascular and tissue injury in liver and tumor that peaked by 72 hours following treatment. The peak microvascular injury and tissue damage in liver (6.6 mm+/-0.2 and 6.3 mm+/-0.2 mm, respectively) was significantly greater than the extent of microvascular and tissue damage in tumors (4.8 mm+/-0.2 mm and 4.5 mm+/-0.2 mm, respectively) (P<0.001). The progression of microvascular injury in liver and tumor at times preceded the tissue injury.

CONCLUSION

Focal hyperthermia produces both progressive microvascular and tissue damage in liver and colorectal liver metastases. An increase in tissue injury following focal hyperthermia may be a direct result of progressive microvascular damage. Tumor vessels appear more susceptible to direct focal hyperthermia destruction than liver sinusoids. The liver sinusoids are however more susceptible to progressive damage or occlusion following the initial laser thermal stimulus.