Lesion progression with time and the effect of vascular occlusion following radiofrequency ablation of the liver

Efficacy and safety of radiofrequency ablation for primary and secondary hyperparathyroidism: a retrospective study

There is now growing interest in the use of Ultrasound-guided radiofrequency ablation (RFA) to treat hyperparathyroidism. But the efficacy and limitations of this treatment have not been described in sufficient detail. Assessing and contrasting the effectiveness and safety of RFA in treating primary hyperparathyroidism (PHPT) and secondary hyperparathyroidism (SHPT). This retrospective study included 57 HPT patients (48 for PHPT and 9 for SHPT) who underwent RFA between January 2017 and April 2021. The serum intact parathyroid hormone (iPTH) and calcium, hyperplastic parathyroid volume, volume reduction rate (VRR) before and after RFA, clinical success rate, symptoms, and complications were analyzed and compared. In SHPT group, bone pain (7/9, 77.8%), skin pruritus (4/9, 44.4%), and multiple hyperplastic parathyroid glands (4/9, 44.4%) were more common compared to the PHPT group. After 12 months of follow-up, the serum iPTH, calcium, and the volume of PHPT and SHPT groups had decreased by more than 60%, 10%, and 90%, respectively (P < 0.05). In the VRR, 13 glands of SHPT (72.2%) and 42 glands of PHPT (87.5%) had achieved the clinical success. In addition, the preoperative and postoperative serum iPTH were higher in the SHPT group than in the PHPT group (P < 0.05). In terms of the serum iPTH and calcium, the PHPT group had substantially higher rates of clinical success, with 42 patients (87.5%) and 46 patients (95.8%) meeting the criteria, respectively compared to 3 patients (33.3%) and 6 patients (66.7%) of SHPT group (P < 0.05). After RFA, the clinical symptoms improved in both groups. The overall incidence of complications (hoarseness and postoperative hematoma) of RFA in the two groups was 10.5% (6/57), and hoarseness (3/9, 33.3%) of SHPT group was more common than PHPT group. All the complications were resolved spontaneously within 12 months after symptomatic treatments. In the treatment of PHPT and SHPT, ultrasound-guided RFA is both successful and safe. PHPT patients have better results in restoring normal iPTH by RFA, and have no considerable difference with the SHPT patients in terms of serum calcium, the volume of the ablation area, and the VRR.

Direct and indirect damage zone of radiofrequency ablation in porcine lumbar vertebra

Objectives

To explore the direct and indirect heat damage zone of radiofrequency ablation (RFA) in porcine vertebrae and to verify the safety of RFA in a vascularized vertebral tumor model.

Methods

RFA was performed in the porcine lumbar vertebrae. Magnetic resonance (MR) imaging, hematoxylin and eosin (HE), and terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) were used to assess the extent of direct and indirect injuries after RFA. The cavity of lumbar vertebrae was made, and the adjacent muscle flap was used to fill the cavity to make a vertebrae tumor model. RFA was performed in the vascularized vertebral tumor model.

Results

T1-weighted images showed a hypointensive region in the center surrounded by a more hypointensive rim on day 0 and 14. T2-weighted images showed that RFA zone was hypointensive on day 0. On day 7, hypointensity was detected in the center surrounded by a hyperintensive rim. HE showed that the RFA zone could be clearly observed on day 14. Thin bone marrow loss areas were seen around the RFA zone, which was consistent with the hyperintensive rim on the T2-weighted images. TUNEL showed a large number of apoptotic cells in the RFA zone. During RFA in the vertebral tumor model, the temperature of all monitoring positions was less than 45 °C.

Conclusion

Using in vivo experiments, the effective zone of RFA was evaluated by MR imaging and pathology, and the direct and indirect damage range were obtained. The safety of RFA was verified by RFA in a vascularized vertebral tumor model.

Differences in the therapeutic effects of high-intensity focused ultrasound (HIFU) ablation on uterine fibroids with different shear wave velocity (SWV): a study of histopathological characteristics

OBJECTIVE

To explore correlations between the therapeutic effect of high intensity focused ultrasound (HIFU) and histopathological characteristics of uterine fibroids with different Shear Wave Velocity (SWV) values.

METHODS

A retrospective study was conducted on 36 women (43 fibroids) who had undergone high intensity focused ultrasound (HIFU) uterine fibroids ablation between January 2019 and January 2020. Preoperative fibroids tissue sections were obtained for histopathological examination. The pathological sections were stained with Masson-trichrome, and were observed and imaged under a Low-power microscope (4 × 10), while the smooth muscle cell (SMC) and collagen fiber content were semi-quantitatively measured. Preoperative fibroid SWV was measured using the Virtual Touch tissue quantification (VTQ) technique. Within one month after HIFU ablation, all patients had undergone a pelvic cavity MRI examination, which measured the size, volume, and non-perfused volume (NPV) of the fibroids. The formula: the ablation rate = NPV/target fibroid volume × 100% was used to calculate the ablation rate of the uterine fibroids. Correlation analysis of SWV values, HIFU ablation rate, along with the smooth muscle cell (SMC) and collagen fiber content, were conducted using the Spearman's correlation test.

RESULTS

The collagen fiber and SMC content of the preoperative fibroids were 32.09 ± 15.90%/view and 37.61 ± 15.32%/view, respectively. Preoperative fibroid SWV value was 3.56 ± 0.71 m/s. Preoperative fibroid SWV was negatively correlated with SMC content (r = -0.445, p = 0.003), but positively correlated with collagen fiber content (r = 0.454, p = 0.002). The ablation rate was negatively correlated with collagen fiber content (r = -0.377, p = 0.013), but positively correlated with SMC content (r = 0.402, p = 0.007).

CONCLUSION

Differences in histopathological characteristics may be important factors that induce differences in the therapeutic effects of HIFU ablation on uterine fibroids with different SWV values.

Thermal ablation of a confluent lesion in the porcine kidney with a clinically available MR-HIFU system

The incidence of small renal masses (SRMs) sized  <4 cm has increased over the decades (as co-findings/or due to introduction of cross sectional imaging). Currently, partial nephrectomy (PN) or watchful waiting is advised in these patients. Ultimately, 80-90% of these SRMs require surgical treatment and PN is associated with a 15% complication rate. In this aging population, with possible comorbidities and poor health condition, both PN and watchful waiting are non-ideal treatment options. This resulted in an increased need for early, non-invasive treatment strategies such as MR-guided high intensity focused ultrasound (MR-HIFU). (i) To investigate the feasibility of creating a confluent lesion in the kidney using respiratory-gated MR-HIFU under clinical conditions in a pre-clinical study and (ii) to evaluate the reproducibility of the MR-HIFU ablation strategy. Healthy pigs (n  =  10) under general anesthesia were positioned on a clinical MR-HIFU system with integrated cooling. A honeycomb pattern of seven overlapping ablation cells (4  ×  4  ×  10 mm³, 450 W, <30 s) was ablated successively in the cortex of the porcine kidney. Both MR thermometry and acoustic energy delivery were respiratory gated using a pencil beam navigator on the contralateral kidney. The non-perfused volume (NPV) was visualized after the last sonication by contrast-enhanced (CE) T ₁-weighted MR (T ₁ w) imaging. Cell viability staining was performed to visualize the extent of necrosis.

RESULTS

a median NPV of 0.62 ml was observed on CE-T ₁ w images (IQR 0.58-1.57 ml, range 0.33-2.75 ml). Cell viability staining showed a median damaged volume of 0.59 ml (IQR 0.24-1.35 ml, range 0-4.1 ml). Overlooking of the false rib, shivering of the pig, and too large depth combined with a large heat-sink effect resulted in insufficient heating in 4 cases. The NPV and necrosed volume were confluent in all cases in which an ablated volume could be observed. Our results demonstrated the feasibility of creating a confluent volume of ablated kidney cortical tissue in vivo with MR-HIFU on a clinically available system using respiratory gating and near-field cooling and showed its reproducibility.

Irreversible Electroporation of the Pancreas Using Parallel Plate Electrodes in a Porcine Model: A Feasibility Study

BACKGROUND

Irreversible electroporation (IRE) with needle electrodes is being explored as treatment option in locally advanced pancreatic cancer. Several studies have shown promising results with IRE needles, positioned around the tumor to achieve tumor ablation. Disadvantages are the technical difficulties for needle placement, the time needed to achieve tumor ablation, the risk of needle track seeding and most important the possible occurrence of postoperative pancreatic fistula via the needle tracks. The aim of this experimental study was to evaluate the feasibility of a new IRE-technique using two parallel plate electrodes, in a porcine model.

METHODS

Twelve healthy pigs underwent laparotomy. The pancreas was mobilized to enable positioning of the paddles. A standard monophasic external cardiac defibrillator was used to perform an ablation in 3 separate parts of the pancreas; either a single application of 50 or 100J or a serial application of 4x50J. After 6 hours, pancreatectomy was performed for histology and pigs were terminated.

RESULTS

Histology showed necrosis of pancreatic parenchyma with neutrophil influx in 5/12, 11/12 and 12/12 of the ablated areas at 50, 100, and 4x50J respectively. The electric current density threshold to achieve necrosis was 4.3, 5.1 and 3.4 A/cm2 respectively. The ablation threshold was significantly lower for the serial compared to the single applications (p = 0.003). The content of the ablated areas differed between the applications: areas treated with a single application of 50 J often contained vital areas without obvious necrosis, whereas half of the sections treated with 100 J showed small islands of normal looking cells surrounded by necrosis, while all sections receiving 4x 50 J showed a homogeneous necrotic lesion.

CONCLUSION

Pancreatic tissue can be successfully ablated using two parallel paddles around the tissue. A serial application of 4x50J was most effective in creating a homogeneous necrotic lesion.

Hyperthermia mediated by dextran-coated La0.7Sr0.3MnO3 nanoparticles: in vivo studies

PURPOSE

The aim of this study was to evaluate radiofrequency-induced dextran-coated lanthanum strontium manganese oxide nanoparticles-mediated hyperthermia to be used for tumor regression in mice.

MATERIALS AND METHODS

Nanoparticles were injected intra-tumorally in melanoma-bearing C57BL/6J mice and were subjected to radiofrequency treatment.

RESULTS

Hyperthermia treatment significantly inhibited tumor growth (~84%), increased survival (~50%), and reduced tumor proliferation in mice. Histopathological examination demonstrated immense cell death in treated tumors. DNA fragmentation, increased terminal deoxynucleotidyl transferase-dUTP nick end labeling signal, and elevated levels of caspase-3 and caspase-6 suggested apoptotic cell death. Enhanced catalase activity suggested reactive oxygen species-mediated cell death. Enhanced expression of heat shock proteins 70 and 90 in treated tumors suggested the possible development of "antitumor immunity".

CONCLUSION

The dextran-coated lanthanum strontium manganese oxide-mediated hyperthermia can be used for the treatment of cancer.

A clinically feasible treatment protocol for magnetic resonance-guided high-intensity focused ultrasound ablation in the liver

OBJECTIVES

Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) allows for noninvasive thermal ablation under real-time temperature imaging guidance. The purpose of this study was to assess the feasibility and safety of MR-HIFU ablation of liver tissue in a clinically acceptable setting. The experimental protocol was designed with a clinical ablation procedure of a small malignant tumor in mind; the procedures were performed within a clinically feasible time frame and care was taken to avoid adverse events. The main outcome was the size and quality of the ablated liver tissue volume on imaging and histology. Secondary outcomes were safety and treatment time.

MATERIALS AND METHODS

Healthy pigs (n = 10) under general anesthesia were positioned on a clinical MR-HIFU system, which consisted of an HIFU tabletop with a skin cooling system integrated into a 1.5-T MR scanner. A liver tissue volume was ablated with multiple sonication cells (4 × 4 × 10 mm, 450 W). Both MR thermometry and sonication were respiratory-gated using a pencil beam navigator on the diaphragm. Contrast-enhanced T1-weighted (CE-T1w) imaging was performed for treatment evaluation. Targeted total treatment time was 3 hours. The abdominal wall, liver, and adjacent organs were inspected postmortem for thermal damage. Ablated tissue volumes were processed for cell viability staining. The ablated volumes were analyzed using MR imaging, MR thermometry, and cell viability histology.

RESULTS

Eleven volume ablations were performed in 10 animals, resulting in a median nonperfused volume (NPV) on CE-T1w imaging of 1.6 mL (interquartile range [IQR], 0.8-2.3; range, 0.7-3.0). Cell viability histology showed a damaged volume of 1.5 mL (IQR, 1.1-1.8; range, 0.7-2.3). The NPV was confluent in 10 of the 11 cases. The ablated tissue volume on cell viability histology was confluent in all 9 available cases. In all cases, there was a good correspondence between the aspects of the NPV on CE-T1w and the ablated volume on cell viability histology. Two treatment-related adverse events occurred: 1 animal had a 7-mm skin burn and 1 animal showed evidence of thermal damage on the surface of the spleen. Median ablation time was 108 minutes (IQR, 101-120; range, 96-181 minutes) and median total treatment time was 180 minutes (IQR, 165-224; 130-250 minutes).

CONCLUSIONS

Our results demonstrate the feasibility and safety of MR-HIFU ablation of liver tissue volumes. The imaging data and cell viability histology show, for the first time, that confluent ablation volumes can be achieved with motion-gated ablation and MR guidance. These results were obtained using a readily available MR-HIFU system with only minor modifications, within a clinically acceptable time frame, and with only minor adverse events. This shows that this technique is sufficiently reliable and safe to initiate a clinical trial.

Real-time monitoring of radiofrequency ablation and postablation assessment: accuracy of contrast-enhanced US in experimental rat liver model

PURPOSE

To examine the accuracy of the unenhanced zone at contrast material-enhanced ultrasonography (US) in predicting coagulative necrosis during and 21 days after radiofrequency (RF) ablation by using radiologic-pathologic comparison.

MATERIALS AND METHODS

Animal studies were approved by the Institutional Animal Care and Use Committee. The livers of 28 rats underwent US-guided RF ablation. In four animals, contrast-enhanced US was performed during ablation and 2 hours and 2, 7, 14, and 21 days after ablation. The unenhanced zone area on US images was measured. DiI-labeled microbubbles were administered during ablation at 2, 4, and 6 minutes or at 2 hours and 2, 7, 14, and 21 days after ablation in the remaining 24 animals (n = 3 at each time point). One minute later, the animal was euthanized, and the ablated liver was harvested. Tissue samples were imaged to quantify total fluorescence, and NADH staining was performed on the same slice. Hematoxylin-eosin staining was also performed. The findings on fluorescence images, NADH-stained images, and hematoxylin-eosin-stained images were compared. The areas of DiI bubble-negative zones, NADH-negative zones, and lightly NADH-staining zones were measured. Data were analyzed by using one-way analysis of variance.

RESULTS

The area of the unenhanced zone on contrast-enhanced US images increased during RF ablation and reached a maximum within 2 days after ablation. At histopathologic examination, a transition zone manifested adjacent to the coagulation zone until 2 days after ablation. The DiI-bubble negative zone on fluorescence images and the damaged zone (transition zone plus coagulation zone) on NADH-stained images increased rapidly within 2 hours after ablation, then slowly reached the maximum on day 2. The ratios of the mean areas of these two zones at hour 2 to those at day 2 were 94.6% and 95.6%, respectively. High uniformity between the damaged zone on NADH-stained images and the DiI bubble-negative zone on fluorescence images was noted at all time points.

CONCLUSION

The temporary transition zone in NADH staining is partially damaged and should transition to nonviability 2 days after ablation. These results demonstrate that contrast-enhanced US can help delineate the maximum area of cell damage (to within 5% of the maximum) as early as 2 hours after ablation. Contrast-enhanced US may be a simple and accurate tool for monitoring the effects of RF ablation and quantifying the size of thermal damage after treatment.

Percutaneous radiofrequency ablation versus partial hepatectomy for small centrally located hepatocellular carcinoma

BACKGROUND

It is not known whether percutaneous radiofrequency ablation (PRFA) could get the same treatment efficacy and fewer complications as partial hepatectomy (PH) in patients with small centrally located hepatocellular carcinoma (HCC). The present study was designed to evaluate the efficacy of PH and PRFA in the treatment of small centrally located HCC.

METHODS

From January 2002 until December 2007, 196 patients with small centrally located HCC (≤5 cm) were included. Of these 196 patients, 94 received PRFA and 102 patients were treated with PH. Treatment outcomes, including major complications and survival data, were studied.

RESULTS

No treatment-related death occurred in either group. There were no significant differences in survival rates between the two groups. The 1-, 3-, and 5-year disease-free survival rates for the PRFA and PH groups were 57.9%, 36.4%, 34.0%, and 59.8%, 42.4%, 40.8%, respectively (P = 0.50). The 1-, 3-, and 5-year overall survival rates for the two groups were 94.3%, 74.7%, and 49.8%, and 89.2%, 74.1%, and 63.1%, respectively (P = 0.96). PRFA had a lower rate of major complications than PH (8.5 vs. 19.6%), and the hospital stay was also shorter in the PRFA group than in the PH subgroup (4 vs. 13 days).

CONCLUSIONS

Based on the data obtained, we concluded that PRFA might be equal to PH for the treatment of small centrally located HCC. However, PRFA has the benefits of shorter hospital stay as well as a lower rate of complications.

High intensity focused ultrasound ablation and antitumor immune response

The ideal cancer therapy not only induces the death of all localized tumor cells without damage to surrounding normal tissue, but also activates a systemic antitumor immunity. High intensity focused ultrasound (HIFU) has the potential to be such a treatment, as it can non-invasively ablate a targeted tumor below the skin surface, and may subsequently augment host antitumor immunity. This paper is to review increasing pre-clinical and clinical evidence linking antitumor immune response to HIFU ablation, and to discuss the potential mechanisms involved in HIFU-enhanced host antitumor immunity. The seminal studies performed so far indicate that although it is not possible to conclude definitively on the connection between HIFU treatment and antitumor immune response, it is nonetheless important to conduct extensive studies on the subject in order to elucidate the processes involved.

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.

Pringle maneuver deteriorates gut barrier dysfunction induced by extended-liver radiofrequency ablation

BACKGROUND

Large volume radiofrequency ablation (RFA) of the liver disrupts intestinal mucosa barrier with subsequent bacterial translocation.

AIMS

To investigate the effect of the Pringle maneuver applied concurrently with extended liver RFA on gut barrier integrity and bacterial translocation.

MATERIALS AND METHODS

Rats were subjected to 30% liver RFA following laparotomy (group RFA), RFA plus 30 min Pringle (group RFA + P), Pringle (group P) or sham operation (group S). Intestinal tissue specimens were excised for histopathological examination and assessment of mucosal morphometry, apoptotic activity, mitotic activity and oxidative state. Tissue specimens were collected from the mesenteric lymph nodes, non-ablated liver parenchyma, kidneys and lungs for bacterial culture. Blood samples were collected from the portal and systemic circulation for endotoxin level measurement.

RESULTS

In group RFA + P, intestinal histopathologic lesions, mucosal atrophy and crypt cell apoptosis were more prominent compared to group RFA. Mitotic activity was suppressed. Oxidative stress was equally induced in all experimental groups. The incidence of positive bacterial cultures, bacterial counts and endotoxin levels were higher in group RFA + P compared to the other groups.

CONCLUSION

The application of the Pringle maneuver concurrently with extended liver RFA aggravates gut barrier dysfunction with more aggressive translocation of endotoxins and intestinal bacteria.

Pringle maneuver exacerbates systemic inflammatory response and multiple-organ injury induced by extended liver radiofrequency ablation

AIM

To assess the systemic inflammatory response (SIR) and the multi-organ damage after large-volume liver radiofrequency ablation (RFA) with or without concurrent Pringle maneuver.

METHODS

Wistar rats were subjected to 30% liver RFA (group RFA), liver RFA under 30-min Pringle maneuver (group RFA + P), Pringle only (group P) or sham operation (group S). Serum levels of interleukin-1α (IL-1α), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), serum biochemical profile, multiple-organ pathology and the activity of nuclear factor-κB (NF-κB) in the liver were assessed post-operatively.

RESULTS

The levels of IL-6 and TNF-α were increased from 1h up to 1w and 6h, respectively, in both RFA groups, while IL-6 was only mildly increased at 3 h in group P. IL-6 was higher in group RFA + P compared to group RFA. Serum biochemical profile was altered more intensely in group RFA + P compared to RFA. There was tissue injury in the non-ablated liver portion as well as in adjacent and remote organs with lesions being more severe in group RFA + P. At 1 h, NF-κB was equally activated in all study groups.

CONCLUSIONS

Extended liver RFA causes SIR and multi-organ injury, which are exacerbated when a concurrent Pringle maneuver is applied.

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.

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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

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

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

Mesna preserves hepatocyte regenerating capacity following liver radiofrequency ablation under Pringle maneuver

BACKGROUND

The objectives of the present study were to test the hypothesis that hepatocyte regenerating activity induced by radiofrequency ablation (RFA) of the liver is attenuated when performed under Pringle maneuver, and to investigate the potentially protective effect of mesna prophylactic administration.

MATERIALS AND METHODS

Wistar rats were subjected to liver RFA (group RFA), RFA plus Pringle maneuver for 30 min (group RFA+P), RFA plus Pringle plus mesna (400mg/kg, per os, 3h prior to operation) (group RFA+P+M), Pringle only (group P), or sham operation (group S) after midline laparotomy. At 1h, liver oxidative state (glutathione to glutathione disulfide ratio-GSH/GSSG) and nuclear factor κB (NF-κB) activity were assessed in liver specimens. At 1, 3, and 6h, the levels of interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α) were measured in blood serum. At 24h, 48 h, 1 wk, and 3 wk, the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were measured in blood serum and the histopathologic profile and hepatocyte mitotic activity were assessed in liver specimens.

RESULTS

Mitotic activity was low but sustained in groups RFA and RFA+P+M, more intense in group P, while suppressed in group RFA+P. Histopathologic profile was deteriorated with lesions being more intense in group RFA+P but significantly less severe in group RFA+P+M. Oxidative stress was equally induced in all experimental groups. NF-κB was activated in groups RFA, RFA+P, and P, but not in group RFA+P+M. IL-6 and TNF-α serum levels were increased; the levels were significantly higher in group RFA+P, while lower in group RFA+P+M. Serum transaminases levels were increased during the first 48 h.

CONCLUSIONS

Hepatocyte regenerating activity is suppressed following liver RFA under Pringle maneuver. Prophylactic administration of mesna preserves hepatocyte regenerating capacity by attenuating acute inflammatory response and minimizing hepatic tissue injury in the non-ablated liver parenchyma.

Effect of vascular occlusion on radiofrequency ablation of the liver in a rabbit VX2 tumor model

AIM: To evaluate the effects of vascular occlusion of hepatic blood flow on radiofrequency lesion and liver injury in rabbit VX2 tumor model.

METHODS: Rabbit VX2 liver tumor models were successfully established, and than they were assigned to two groups: radiofrequency ablation alone group and radiofrequency ablation with hepatic blood flow occlusion (vascular-occluded RFA) group. Radiofrequency lesions were created in vivo using a cool-tip radiofrequency electrode (radiofrequency parameters were 8 min in time and 30 W in power). The hepatic blood flow occlusion was got by pringle maneuver. Serum ALT, AST, AKP and GGT were detected before the operation and the 1^st, 3^rd, 7^th day after the operation, and the adverse events were observed. The animals were sacrificed one week later. The size, volume of necrosis lesions in the two groups were then analyzed.

RESULTS: Volume and vertical diameter of the coagulated area were significantly greater with the pringle maneuver. The parallel diameter was larger than that coagulated by standard RFA, but there were no significantly differences between the groups. Serum ALT, GGT was higher in radiofrequency ablation combined with Pringle maneuver group than radiofrequency ablation alone group at each time after the operation (P < 0.05), and serum GGT lever was gradually increased postoperatively. Differences in serum AST, AKP between the two groups at each time postoperatively were not significant. One case of vascular-occluded RFA group was complicated with mild bile leakage, one case died on the 1^st day for hemorrhage, and one case died for liver injury on the 4^th day.

CONCLUSION: Radiofrequency ablation combined with occlusion of the hepatic artery and portal vein increases the volume of necrosis when compared with radiofrequency ablation alone, but much more serious liver injuries are found, careful attention should be paid when this technique is used in clinical practice.

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.

Role of B-mode ultrasound screening in detection of local tumor recurrence in the first year after radiofrequency ablation in the liver

BACKGROUND

Ultrasound is known to be useful in imaging radiofrequency ablation (RFA) lesions intra- and postoperatively. The presented study intends to prove the value of ultrasound examination as a means of screening RFA-treated patients for local tumor recurrence.

PATIENTS AND METHODS

During a period of 47 months, 91 RFA treatments were performed in 61 patients in a single institution. Indications for RFA were hepatocellular carcinoma (74%), colorectal metastases (18%), recurrent cholangiocellular carcinoma (5%) and one neuroendocrine tumor metastasis as well as one metastasis of pancreatic cancer (1.5% each). RFA was only considered in non-resectable liver cancer. All applications were conducted under sonographic guidance following preoperative evaluation. Postoperative screening included sonographic examinations at intervals of 3, 6 and 12 months postoperatively, and further annual follow-up examinations. Mean follow-up period was 11.8 months.

RESULTS

Within the first 12 months after treatment, the lesions become more and more inhomogenous with mixed echogeneity. Occasionally, this evolves as a misleading finding, mimicking early tumor recurrence. To clarify suspicious cases (31%), magnetic resonance imaging (20%) or computed tomography (10%) was engaged. Ultrasound led to the detection of local tumor recurrence in 78% of recurrent HCC (13 patients), but only in 67% of metastatic diseases (3 patients). Overall local recurrence rate was 18%.

CONCLUSION

Ultrasound screening as a follow-up of primary hepatic malignancies is, due to its sensitivity, capable of detecting early local recurrence despite its low specifity. Appropriate application of particular criteria of local recurrence allows B-mode ultrasound to play a major role in screening RFA-treated patients.

Laparoscopic radiofrequency of hepatocellular carcinoma using ultrasound-guided selective intrahepatic vascular occlusion

BACKGROUND

The optimal treatment for hepatocellular carcinoma (HCC) is surgical resection. However, only a small percentage of patients are operative candidates. The authors aimed to assess a novel operative combination of laparoscopic radiofrequency (LRF) with a selective intrahepatic vascular occlusion (SIHVO) to obtain an increased rate of total necrosis and a reduced rate of local HCC recurrences.

METHODS

For this study, 37 patients with HCC in liver cirrhosis were submitted to LRF with SIHVO. An LRF was indicated for patients not amenable to liver resection who evidenced at least one of the following criteria: severe impairment of the coagulation tests, large tumors (but <5 cm) or multiple lesions requiring repeated punctures, superficial lesions adjacent to visceral structures, deep-sited lesions with a very difficult or impossible percutaneous approach, and short-term recurrence of HCC after percutaneous loco-regional therapies.

RESULTS

Laparoscopic ultrasound identified seven new malignant lesions (19%) undetected by preoperative imaging. There was no operative mortality. Of the 37 patients, 31 experienced no complications (84%). Computed tomography (CT) evaluation 1 month after treatment showed that a complete response with 100% necrosis had been achieved for all the patients (100%). During the follow-up period (mean, 11.8 +/- 8.2 months), new malignant nodules developed in 14 patients (42%), and 36% of these recurrences were located in the same treated segment of the HCC.

CONCLUSIONS

The combined LRF and SIHVO procedure proved to be a safe and effective technique at least in the short and mid term. In fact, it permitted the treatment of lesions not treatable using the percutaneous approach with a complete clearance, and it had a low morbidity rate.

Assessment of systemic inflammatory response (SIR) in patients undergoing radiofrequency ablation or partial liver resection for liver tumors

INTRODUCTION

Local therapies for liver tumors are considered to be safe. However, cryoablation (CA) has been associated with an exaggerated systemic inflammatory response (SIR). Aim of this study was to assess the degree of SIR after radiofrequency ablation (RFA) in comparison with major (MR) or minor (mR) liver resection.

MATERIAL AND METHODS

Thirty-nine patients were treated with RFA (n = 11), MR (n = 10) or mR (n = 18). SIR parameters [white blood count (WBC) and C-reactive protein (CRP)], proinflammatory mediators [IL-6, TNF-alpha and sPLA2], liver damage parameters [AST/ALT] and platelet counts were determined at different time points. The volume of ablated liver was calculated on the first CT after RFA in order to correlate ablated liver volume with liver enzyme release and SIR. All data are expressed as median values with quartiles [25%, 75%].

RESULTS

RFA induced a moderate SIR, as demonstrated by a significant elevation of CRP (77 mg/L vs 3 mg/L), IL-6 (96 pg/ml vs 4 pg/ml) and sPLA2 (41 ng/ml vs 7 ng/ml, p < 0.05). Peak point values of SIR (WBC and CRP at 24 vs 48 h and 48 vs 72 h) and proinflammatory response parameters (24 vs 48 h) occurred earlier after RFA than after mR or MR. Time-to-time comparison revealed even increased levels of CRP (77 mg/L [59, 160]) 24h after RFA when compared to patients undergoing major or minor resection (50 mg/L [28, 66] and 59 mg/L [24, 91], respectively) and increased levels of IL-6 (67 pg/ml [42, 131]) 4 h after RFA when compared to patients undergoing minor resection (29 pg/ml [20, 55]). Postoperative levels of AST and LDH correlated significantly with the ablated liver volume 1h after RFA (RC = 0.860 and RC = 0.868, respectively, p < 0.05).

CONCLUSION

RFA induced a moderate SIR of the same magnitude as in patients undergoing partial liver resection. None of the patients showed signs of an exaggerated SIR, as has been reported after cryoablation.

Experimental and Clinical Radiofrequency Ablation: Proposal for Standardized Description of Coagulation Size and Geometry

BACKGROUND

Radiofrequency (RF) ablation is used to obtain local control of unresectable tumors in liver, kidney, prostate, and other organs. Accurate data on expected size and geometry of coagulation zones are essential for physicians to prevent collateral damage and local tumor recurrence. The aim of this study was to develop a standardized terminology to describe the size and geometry of these zones for experimental and clinical RF.

METHODS

In a first step, the essential geometric parameters to accurately describe the coagulation zones and the spatial relationship between the coagulation zones and the electrodes were defined. In a second step, standard terms were assigned to each parameter.

RESULTS

The proposed terms for single-electrode RF ablation include axial diameter, front margin, coagulation center, maximal and minimal radius, maximal and minimal transverse diameter, ellipticity index, and regularity index. In addition a subjective description of the general shape and regularity is recommended.

CONCLUSIONS

Adoption of the proposed standardized description method may help to fill in the many gaps in our current knowledge of the size and geometry of RF coagulation zones.

Technology insight: Image-guided therapies for hepatocellular carcinoma--intra-arterial and ablative techniques

Locoregional techniques have become the mainstay of therapy for patients with unresectable hepatocellular carcinoma (HCC). Such image-guided interventions include catheter-based approaches (transarterial chemoembolization and yttrium-90 radiotherapy) and locoregional ablative techniques, either chemical (percutaneous ethanol injection), or thermal (radiofrequency ablation, laser ablation, microwave ablation and cryoablation). These therapies are mainly utilized for palliation, but have also been used with curative intent. In selected cases, percutaneous interventional treatments have shown good results (5-year survival 40-50%), but, even when chosen as first-line treatment, have not been able to achieve the response rates and outcomes achieved by surgical options (resection or transplantation). New promising image-guided therapies are continuously emerging, as we attempt to improve tumor targeting, minimize hepatic toxicity and ultimately improve quality of life and survival of patients with HCC. With new technologies in imaging and drug delivery becoming available, it is likely that, in the future, patients with HCC will be best treated by a multidisciplinary team approach, utilizing a combination of techniques to improve patient survival. This review outlines the current status of the most commonly used image-guided locoregional interventions in the treatment of patients with HCC, and describes recent research and advances related to image-guided interventions for liver cancer.

Selective portal clamping to minimize hepatic ischaemia-reperfusion damage and avoid accelerated outgrowth of experimental colorectal liver metastases

BACKGROUND

Temporary vascular clamping during local ablation for colorectal liver metastases increases destruction volumes. However, it also causes ischaemia-reperfusion (IR) injury to the liver parenchyma and accelerates the outgrowth of microscopic tumour deposits. The aim of this study was to investigate the effects of selective portal clamping on hepatocellular damage and tumour growth.

METHODS

Mice carrying pre-established hepatic colorectal micrometastases underwent either simultaneous clamping of both the portal vein and the hepatic artery or selective clamping of the portal vein to the median and left liver lobes for 45 min. Sham-operated mice served as controls. Hepatic injury and tumour growth were assessed over time.

RESULTS

Standard inflow occlusion resulted in a rise in liver enzymes, a local inflammatory response and hepatocellular necrosis. The outgrowth of pre-established micrometastases was accelerated three- to fourfold in clamped compared with non-clamped liver lobes (27.4 versus 7.8 per cent, P < 0.010). Conversely, selective portal clamping induced minimal liver injury, tissue inflammation or hepatocellular necrosis, and completely stopped the accelerated outgrowth of micrometastases.

CONCLUSION

Selective portal clamping does not induce liver tissue damage or accelerate micrometastasis outgrowth and may therefore be the preferable clamping method during local ablative treatment of hepatic metastases.

The surgical approach for radiofrequency ablation of liver tumors

Radiofrequency ablation for the treatment of liver tumors is one of the best alternative treatment modalities when surgical resection is not possible. To find the right indication for the treatment, every patient should be treated in a high-volume center for the treatment of liver tumors in an interdisciplinary conference consisting of liver surgeons, interventional radiologists, medical oncologists, and gastroenterologists. With a multimodal approach including anatomic segmental and wedge resection of the liver, RFA, and chemotherapy, a median survival of 36 months was achieved in technically unresectable patients with colorectal liver metastases (Elias et al. 2005). This survival doubles the survival rate of any other treatment modality in this group of patients. These interdisciplinary conferences also serve to determine the approach for RFA, whether it should be percutaneous, laparoscopic, or open surgery. The safest ablation with the fewest adverse events from RFA is the open surgical approach, followed by the laparoscopic approach. The approach with the highest risk of injury to organs in proximity to the liver is the percutaneous approach. Therefore, many variables must be evaluated before making definite decisions. After choosing RFA as the best alternative treatment option after evaluation of all variables for a particular patient, it offers a treatment option with a potential cure. A major advantage is the possible combination with liver resection, which extends the indication for surgical or ablative therapy.

Factors influencing the local failure rate of radiofrequency ablation of colorectal liver metastases

BACKGROUND

The prognosis of patients with colorectal cancer is poor, especially when there is distant metastatic disease. Local ablation of tumor by radiofrequency ablation (RFA) has emerged as a safe and effective new treatment modality, but its long-term efficacy may be hindered by renewed local tumor growth at the site of RFA. The objectives of this study were to identify risk factors for local RFA failure and to define exclusion criteria for RFA treatment of colorectal liver metastases.

METHODS

A total of 199 lesions in 87 patients were ablated with RFA. Factors influencing local failure rates were identified and compared with data from the literature.

RESULTS

The local failure rate was 47.2%, and the average time to local disease progression was 6.5 months. Factors that significantly correlated with increased failure rates were metachronous occurrence of liver metastases, large mean lesion size, and central tumor location.

CONCLUSIONS

Because accurate electrode placement is pivotal in achieving adequate tumor necrosis, RFA should not be performed percutaneously when electrode placement is impaired. We suggest that lesions >5 cm and lesions located near great vessels or adjacent organs should be treated with open RFA, thus allowing vascular inflow occlusion and complete mobilization of the liver. Lesions that are difficult to reach by electrodes should be approached by an open procedure.

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.

Bipolar radiofrequency ablation of liver metastases during laparotomy. First clinical experiences with a new multipolar ablation concept

BACKGROUND AND OBJECTIVE

Radiofrequency ablation (RFA) is a promising method for local treatment of liver malignancies. Currently available systems for radiofrequency ablation use monopolar current, which carries the risk of uncontrolled electrical current paths, collateral damages and limited effectiveness. To overcome this problem, we used a newly developed internally cooled bipolar application system in patients with irresectable liver metastases undergoing laparotomy. The aim of this study was to clinically evaluate the safety, feasibility and effectiveness of this new system with a novel multipolar application concept.

PATIENTS AND METHODS

Patients with a maximum of five liver metastases having a maximum diameter of 5 cm underwent laparotomy and abdominal exploration to control resectability. In cases of irresectability, RFA with the newly developed bipolar application system was performed. Treatment was carried out under ultrasound guidance. Depending on tumour size, shape and location, up to three applicators were simultaneously inserted in or closely around the tumour, never exceeding a maximum probe distance of 3 cm. In the multipolar ablation concept, the current runs alternating between all possible pairs of consecutively activated electrodes with up to 15 possible electrode combinations. Post-operative follow-up was evaluated by CT or MRI controls 24-48 h after RFA and every 3 months.

RESULTS

In a total of six patients (four male, two female; 61-68 years), ten metastases (1.0-5.5 cm) were treated with a total of 14 RF applications. In four metastases three probes were used, and in another four and two metastases, two and one probes were used, respectively. During a mean ablation time of 18.8 min (10-31), a mean energy of 48.8 kJ (12-116) for each metastases was applied. No procedure-related complications occurred. The patients were released from the hospital between 7 and 12 days post-intervention (median 9 days). The post-interventional control showed complete tumour ablation in all cases.

CONCLUSIONS

Bipolar radiofrequency using the novel multipolar ablation concept permits a safe and effective therapy for the induction of large volumes of coagulation in the local treatment of liver metastases.

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.

Extension of radiofrequency ablation of the liver by transcatheter arterial embolization with iodized oil and gelatin sponge: results in a pig model

PURPOSE

To determine whether transcatheter arterial embolization (TAE) with iodized oil and gelatin sponge particles can be used to expand radiofrequency (RF)-induced coagulation necrosis, the morphology and histologic characteristics of ablation lesions were evaluated in the normal pig liver after three different TAE procedures.

MATERIALS AND METHODS

Ten consecutive animals with 33 ablation lesions produced with an RF ablation system were randomly assigned to one of three treatment groups and a control group: a group treated with TAE with iodized oil, a group treated with TAE with gelatin sponge, a group treated with TAE with iodized oil and gelatin sponge, and a control group in which TAE was not performed. After the completion of ablation, the lesions were excised for gross and histologic examination.

RESULTS

The longest and shortest diameters of ablation lesions were greatest in the group treated with TAE with iodized oil and gelatin sponge, followed by the groups treated with TAE with gelatin sponge and TAE with iodized oil (P < .05 vs controls, respectively). The hemorrhagic rim was also widest in the group treated with TAE with iodized oil and gelatin sponge (P < .05 vs controls), and it spread toward the liver periphery like a segmental hemorrhagic area adjacent to the ablation lesion. Histochemical staining for lactate dehydrogenase, maleate dehydrogenase, and nicotinamide adenine dinucleotide diaphorase showed what appeared to be 100% cellular destruction in all the ablation lesions and their hemorrhagic rims.

CONCLUSION

RF ablation combined with TAE with iodized oil and gelatin sponge induces the greatest area of coagulation necrosis accompanied by peripherally spreading segmental necrosis in normal pig liver tissue.

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.

Outcome of regional and local ablative therapies for hepatocellular carcinoma: a collective review

BACKGROUND

Transcatheter arterial (chemo) embolization (TACE), cryoablation (CA) and percutaneous ethanol injection (PEI) were the first regional and local ablative techniques that came into use for irresectable HCC. Radiofrequency ablation (RFA) and interstitial laser coagulation (ILC) followed and have now evolved rapidly. It would not be ethical to compare resection with ablation in patients well enough to undergo major surgery. Therefore, hepatic resection and hepatic transplantation remain the only curative treatment options for HCC.

METHODS

On the basis of a Medline literature search and the authors' experiences, the principles, current status and prospects of TACE and local ablative techniques in HCC are reviewed.

RESULTS

Complete tumour necrosis can be achieved in 60-100% of patients treated with PEI (70-100%), cryoablation (60-85%), RFA (80-90%) or ILC (70-97%). After TACE significant tumour response is achieved in 17-61.9% but complete tumour response is rare (0-4.8%) as viable tumour cells remain after TACE. Five-year survival rates are available for TACE (1-8%), PEI (0-70%) and cryoablation (40%). Only PEI and RFA were compared in one RCT. RFA was associated with fewer treatment sessions and a higher complete necrosis rate. Furthermore, all techniques are associated with low morbidity and mortality, but cryoablation seems to be associated with a higher morbidity rate.

CONCLUSION

TACE has shown to be a valuable therapy with survival benefits in strictly selected patients with unresectable HCC. RFA and PEI are now considered as the local ablative techniques of choice for the treatment of, preferably small, HCC. When tumours are located close to bile ducts or large vessels, PEI remains a valuable therapy. Completeness of ablation can be more easily monitored during cryoablation and another advantage of cryoablation is the possibility of edge freezing. The results of ILC are comparable to RFA with only few side effects and high tumour response rates.

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.

Survival and intra-hepatic recurrences after laparoscopic radiofrequency of hepatocellular carcinoma in patients with liver cirrhosis

BACKGROUND

The optimal treatment for hepatocellular carcinoma (HCC) is surgical resection. However, only a small percentage of patients are operative candidates. Percutaneous radiofrequency interstitial thermal ablation proved to be effective, too. Our objective was to assess a novel operative combination of laparoscopic ultrasound (LUS) with laparoscopic radiofrequency (LRF) in the treatment of HCC not amenable to liver resection.

METHODS

One hundred and four patients with HCC in liver cirrhosis were submitted to laparoscopic LRF. A LRF was indicated in patients not amenable to liver resection that had at least one of the following criteria: (a) severe impairment of the coagulation tests; (b) large tumors (but <5 cm) or multiple lesions requiring repeated punctures; (c) superficial lesions adjacent to visceral structures; (d) deep-sited lesions with a very difficult or impossible percutaneous approach; (e) short-term recurrence of HCC following percutaneous loco-regional therapies.

RESULTS

The LRF procedure was completed in 102 out of 104 patients (98% feasibility rate). LUS identified 26 new malignant lesions (25%) undetected by pre-operative imaging. There was no operative mortality. Seventy-six patients had no complication (73%). At 1-month computed tomography (CT) evaluation, a complete response with a 100% necrosis was achieved in 88 out of 101 patients (87%). During the follow-up (mean follow-up: 22.5 +/- 15.9 months), 55 patients (54%) developed new malignant nodules (42% of these recurrences were localized in the same segment of the HCC treated).

CONCLUSIONS

LRF of HCC proved to be a safe and effective technique at least in the short and mid-term: in fact it permits to treat lesions not treatable with the per cutaneous approach, to detect 25% of new HCC nodules and it has a low morbidity rate.

Focal hyperthermia produces progressive tumor necrosis independent of the initial thermal effects

Focal hyperthermia, produced using laser, radio frequency, and microwave, is used to treat liver tumors. The exact mechanisms of tissue destruction using focal hyperthermia are, however, unknown. Clinical and experimental studies suggest a progression of injury after cessation of the initial heat stimulus. This study investigates the mechanisms and time sequence of progressive tissue necrosis induced using focal hyperthermia in a murine model of colorectal liver metastases. Focal hyperthermia produced using a neodymium-yttrium aluminum garnet (Nd-YAG) laser source was applied to the normal liver and colorectal cancer liver metastases in inbred male CBA strain mice. The extent of direct lethal thermal injury was assessed histochemically using vital stain for nicotinamide adenine dinucleotide (NADH) diaphorase immediately after laser application. Tissue injury at subsequent time points was assessed using both NADH diaphorase staining and routine histology to determine the temporal relationship between tissue necrosis and time. Thermal injury occurring immediately after the application of 100 joules of energy was greater in the tumor tissue than in the normal liver (mean [standard error of the mean (SEM)]), measuring 23.5 (3.4) and 16.3 (2.6) mm(3), respectively (P=0.046), despite similar tissue temperature profiles. There was a significant increase in tissue necrosis after initial injury that was greater in the normal liver than in the tumor tissue. In the normal liver, the peak volume of necrosis was 137.4 (9.8) mm(3) and occurred at 3 days, whereas in the tumor tissue the peak was 49.0 (3.5) mm(3) at 4.5 days (P < 0.001). Focal hyperthermia produces tissue necrosis that occurs in two phases. The first phase is caused by the direct lethal thermal injury followed by a second phase involving a progression of necrosis beyond the initial thermal effects. The normal liver and the tumor tissue responded differently to focal hyperthermia. In the tumor tissue, the direct injury is more pronounced, whereas the progression of injury is more rapid and extensive in the normal liver.

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.

Radiofrequency ablation of primary and metastatic hepatic malignancies

Radiofrequency interstitial tissue ablation is a local ablative therapy in which tumors are destroyed in situ by thermal coagulation and protein denaturation through frictional heating produced by tissue ionic agitation from high-frequency alternating current. This technology can be used to destroy primary and metastatic hepatic lesions generally considered nonresectable or nonoperable, thus providing patients with these tumors, who have few treatment options, a relatively safe and effective alternative with the potential for improved chance of survival. Knowledge of the broad spectrum of potential complications associated with radiofrequency ablation (RFA) is essential for prevention, early detection, and proper management. Combining RFA with other modalities such as surgical resection or hepatic artery infusional chemotherapy is feasible, has increased the pool of operable patients, and may improve treatment efficacy and clinical outcome in properly selected patients. The approach to perform RFA percutaneously, laparoscopically, or during laparatomy should take into consideration tumor characteristics, imaging and technical limitations, and the role of other treatment modalities. Therefore, patients considered for RFA should be evaluated within the context of a multidisciplinary approach to insure proper patient selection and coordination of adjunct therapy.

Radiofrequency ablation of cancer

Radiofrequency ablation (RFA) has been used for over 18 years for treatment of nerve-related chronic pain and cardiac arrhythmias. In the last 10 years, technical developments have increased ablation volumes in a controllable, versatile, and relatively inexpensive manner. The host of clinical applications for RFA have similarly expanded. Current RFA equipment, techniques, applications, results, complications, and research avenues for local tumor ablation are summarized.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Variability of Size and Shape of Necrosis Induced by Radiofrequency Ablation in Human Livers: A Volumetric Evaluation

BACKGROUND

Definite size and shape of radiofrequency-induced ablations (RFAs) cannot be evaluated intraoperatively. Instead, surgeons choose a radiofrequency device that is supposed to cause a necrosis of a determined size greater than the malignant lesion. The aim of this study was to measure the variability of the induced necroses postoperatively and to define a reproducible ablation volume in human liver.

METHODS

In 24 patients, 34 RFA procedures were performed with single applications of the device. The deployment was 3 cm (n=16), 4 cm (n=5), or 5 cm (n=13). The induced necroses were analyzed by volumetric reconstructions of computed tomography (CT) scans. Measured volumes were compared with the expected volumes. Furthermore, the shape of the necrosis was classified according to an index of the diameters.

RESULTS

The measured volumes of postoperative necroses were 14 +/- 8 cm3 (deployment, 3 cm), 24 +/- 12 cm3 (4 cm), and 45 +/- 42 cm3 (5 cm). The diameter of a sphere fitted into the necroses reached 2.9 +/- .5 cm (3 cm), 3.5 +/- .7 cm (4 cm), and 4.1 +/- 1.1 cm (5 cm), at P<.02, significantly smaller than the deployment. The classification of shapes yielded a spherical shape (n=14), a teardrop shape (n=13), or an irregular shape (n=7). The energy consumption was 2.1 +/- 1.5 kJ/cm3 (3 cm), 2.6 +/- .5 kJ/cm3 (4 cm), or 3.5 +/- 2.0 kJ/cm3 (5 cm).

CONCLUSIONS

The diameter of RFA-induced liver necrosis is significantly smaller than expected from needle deployment, especially with full-needle deployment. The shape of the lesion differs in more than half of the cases from the anticipated spherical pattern. The upper limit for reproducible necrosis induction is a tumor diameter of 3.4 cm.

Hepatic vascular inflow occlusion enhances tissue destruction during cryoablation of porcine liver1

BACKGROUND

Local recurrences after cryoablation of liver tumors have been reported at rates from 5% to 44% and can be caused by inadequate coverage of the tumor by the frozen region. Hepatic vascular inflow occlusion may facilitate ablation by enlarging the size of the frozen region and the tissue necrosis induced by freezing. Few studies have documented these effects of inflow occlusion during liver cryoablation.

MATERIALS AND METHODS

Two cryolesions were induced in the liver of 12 pigs in a standardized set-up. Vascular inflow occlusion was used in six pigs during freezing. Two freeze cycles were performed at each location. Ice-ball volume was estimated by intraoperative magnetic resonance imaging. Cryolesion volume was estimated from histopathologic examination of the lesions 4 days after ablation.

RESULTS

The median volume of ice-balls produced during inflow occlusion was 107% larger than for ice-balls produced without occlusion (P < 0.001). The median volume of cryolesions made during inflow occlusion was 195% larger than for cryolesions induced without occlusion (P < 0.001). The geometry of the ice-balls was more regular if produced during inflow occlusion than if not. The ice-balls produced during the second freeze cycle were 17% and 20% larger than the ice-ball produced during the first freeze for lesions made with (P = 0.01) and without (P = 0.03) inflow occlusion.

CONCLUSIONS

Hepatic vascular inflow occlusion enables freezing of larger volumes of liver tissue andincreases the volume of tissue necrosis induced during cryoablation of porcine liver.