Optimal strategies for combining transcatheter arterial chemoembolization and radiofrequency ablation in rabbit VX2 hepatic tumors

Ultrasound-mediated nano-sized drug delivery systems for cancer treatment: Multi-scale and multi-physics computational modeling

Computational modeling enables researchers to study and understand various complex biological phenomena in anticancer drug delivery systems (DDSs), especially nano-sized DDSs (NSDDSs). The combination of NSDDSs and therapeutic ultrasound (TUS), that is, focused ultrasound and low-intensity pulsed ultrasound, has made significant progress in recent years, opening many opportunities for cancer treatment. Multiple parameters require tuning and optimization to develop effective DDSs, such as NSDDSs, in which mathematical modeling can prove advantageous. In silico computational modeling of ultrasound-responsive DDS typically involves a complex framework of acoustic interactions, heat transfer, drug release from nanoparticles, fluid flow, mass transport, and pharmacodynamic governing equations. Owing to the rapid development of computational tools, modeling the different phenomena in multi-scale complex problems involved in drug delivery to tumors has become possible. In the present study, we present an in-depth review of recent advances in the mathematical modeling of TUS-mediated DDSs for cancer treatment. A detailed discussion is also provided on applying these computational models to improve the clinical translation for applications in cancer treatment. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Radiofrequency ablation in the treatment of hepatocellular carcinoma

OBJECTIVE

The purpose of this article is to discuss the use, comparative efficacy, and research progress of radiofrequency ablation (RFA), alone or in combination with other therapies, for the treatment of hepatocellular carcinoma (HCC).

METHOD

To search and summarize the basic and clinical studies of RFA in recent years.

RESULTS

RFA is one of the radical treatment methods listed in the guidelines for the diagnosis and treatment of HCC. It has the characteristics of being minimally invasive and safe and can obtain good local tumor control, and it can improve the local immune ability, improve the tumor microenvironment and enhance the efficacy of chemotherapy drugs. It is commonly used for HCC treatment before liver transplantation and combined ALPPS and hepatectomy for HCC. In addition, the technology of RFA is constantly developing. The birth of noninvasive, no-touch RFA technology and equipment and the precise RFA concept have improved the therapeutic effect of RFA.

CONCLUSION

RFA has good local tumor control ability, is minimally invasive, is safe and has other beneficial characteristics. It plays an increasingly important role in the comprehensive treatment strategy of HCC. Whether RFA alone or combined with other technologies expands the surgical indications of patients with HCC and provides more benefits for HCC patients needs to be determined.

Impact of Chemoembolic Regimen on Immune Cell Recruitment and Immune Checkpoint Marker Expression following Transcatheter Arterial Chemoembolization in a VX2 Rabbit Liver Tumor Model

PURPOSE

To characterize the effects of commonly used transcatheter arterial chemoembolization (TACE) regimens on the immune response and immune checkpoint marker expression using a VX2 rabbit liver tumor model.

MATERIALS AND METHODS

Twenty-four VX2 liver tumor-bearing New Zealand white rabbits were assigned to 7 groups (n = 3 per group) undergoing locoregional therapy as follows: (a) bicarbonate infusion without embolization, (b) conventional TACE (cTACE) using a water-in-oil emulsion containing doxorubicin mixed 1:2 with Lipiodol, drug-eluting embolic-TACE with either (c) idarubicin-eluting Oncozene microspheres (40 μm) or (d) doxorubicin-eluting Lumi beads (40-90 μm). For each therapy arm (b-d), a tandem set of 3 animals with additional bicarbonate infusion before TACE was added, to evaluate the effect of pH modification on the immune response. Three untreated rabbits served as controls. Tissue was harvested 24 hours after treatment, followed by digital immunohistochemistry quantification (counts/μm² ± SEM) of tumor-infiltrating cluster of differentiation 3⁺ T-lymphocytes, human leukocyte antigen DR type antigen-presenting cells (APCs), cytotoxic T-lymphocyte-associated protein-4 (CTLA-4), and programmed cell death protein-1 (PD-1)/PD-1 ligand (PD-L1) pathway axis expression.

RESULTS

Lumi-bead TACE induced significantly more intratumoral T-cell and APC infiltration than cTACE and Oncozene-microsphere TACE. Additionally, tumors treated with Lumi-bead TACE expressed significantly higher intratumoral immune checkpoint markers compared with cTACE and Oncozene-microsphere TACE. Neoadjuvant bicarbonate demonstrated the most pronounced effect on cTACE and resulted in a significant increase in intratumoral cluster of differentiation 3⁺ T-cell infiltration compared with cTACE alone.

CONCLUSIONS

This preclinical study revealed significant differences in evoked tumor immunogenicity depending on the choice of chemoembolic regimen for TACE.

Combined Transarterial Chemoembolization with Microwave Ablation versus Microwave Alone for Treatment of Medium Sized Hepatocellular Carcinoma

Background & Aims:

Hepatocellular carcinoma (HCC) is the fifth most common cancer and the second leading cause of cancer-related deaths. The only definitive treatment for both HCC and cirrhosis is liver transplantation, but long wait times in some regions and a relatively fixed number of donor organs negatively impact access to liver transplantation. The aim of the work was to evaluate and compare the short outcome of patients with medium-sized HCC who will undergo percutaneous microwave ablation (MWA) alone and in combination with TACE.

Methods:

This prospective study included 40 patients with medium-sized HCC lesions who were classified into two groups; Group A that included twenty patients treated by TACE followed by percutaneous MWA after 2 weeks and group B that included twenty patients treated by 2 sessions of percutaneous MWA with 2 weeks interval. Full history taking, clinical examination, laboratory investigation, abdominal ultrasonography and abdominal tri-phasic computed tomography (CT) with contrast were obtained from the two groups. Laboratory and radiological follow up of the cases were done at 1 and 3 months after the treatment.

Results:

There was no statistically significant difference in the sociodemographic criteria, laboratory measurement and clinical criteria between the cases in the two study groups before initiation of treatment. The response was slightly better in the combined treatment group, but it did not show a statistically significant difference. The incidence of complications was higher in the MWA group.

Conclusion::

Hepatocellular carcinoma is a common complication of HCV related cirrhosis. Association of TACE-MWA led to better response rates than MWA with fewer complications.

In the Era of Systemic Therapy for Hepatocellular Carcinoma Is Transarterial Chemoembolization Still a Card to Play?

Conventional transarterial embolization (cTACE) has been proven to be effective for intermediate stage hepatocellular carcinoma (HCC), with a recent systematic review showing an overall survival (OS) of 19.4 months. Nevertheless, due to the rapid development of the systemic therapeutic landscape, the place of TACE is becoming questionable. Is there still a niche for TACE in the era of immunotherapy and combination treatments such as atezolizumab-bevacizumab, which has shown an OS of 19.2 months with excellent tolerance? The development of drug-eluting microspheres (DEMs) has led to the standardization of the technique, and along with adequate selection, it showed an OS of 48 months in a retrospective study. In order to increase treatment selectivity, new catheters have also been added to the TACE arsenal as well as the use of cone-beam CT (CBCT), which provides three-dimensional volumetric images and guidance during procedures. Moreover, the TACE indications have also widened. It may serve as a "bridging therapy" for liver transplantation candidates while they are on the waiting list, and it represents a valuable downstaging tool to transplantation criteria. The aim of this review is to explore the current data on the advancements of TACE and its future place amongst the growing panel of treatments.

Combined therapy with conventional trans-arterial chemoembolization (cTACE) and microwave ablation (MWA) for hepatocellular carcinoma >3-<5 cm

PURPOSE

To compare safety and efficacy of combined therapy with conventional transarterial chemoembolization (cTACE)+microwave ablation (MWA) versus only TACE or MWA for treatment of hepatocellular carcinoma (HCC) >3-<5 cm.

METHODS

This randomized controlled trial (NCT04721470) screened 278 patients with HCC >3-<5 cm. Patients were randomized into three groups: 90 underwent TACE (Group 1); 95 underwent MWA (Group 2); and 93 underwent combined therapy (Group 3). Patients were followed-up with contrast-enhanced CT or MRI. Images were evaluated and compared for treatment response and adverse events based on modified response evaluation criteria in solid tumor. Serum alpha-fetoprotein (AFP) concentration was measured at baseline and during every follow-up visit.

RESULTS

Final analysis included 265 patients (154 men, 111 women; mean age = 54.5 ± 11.8 years; range = 38-76 years). Complete response was achieved by 86.5% of patients who received combined therapy compared with 54.8% with only TACE and 56.5% with only MWA (p = 0.0002). The recurrence rate after 12 months was significantly lower in Group 3 (22.47%) than Groups 1 (60.7%) and 2 (51.1%) (p = 0.0001). The overall survival rate (three years after therapy) was significantly higher in Group 3 (69.6%) than Groups 1 (54.7%) and 2 (54.3%) (p = 0.02). The mean progression-free survival was significantly higher in Group 3 than groups 1 and 2 (p < 0.001). A decrease in AFP concentration was seen in 75%, 63%, and 48% patients of Group 3, 2, and 1, respectively.

CONCLUSIONS

Combined therapy with cTACE + MWA is safe, well-tolerated, and more effective than TACE or MWA alone for treatment of HCC >3-<5 cm.

Cerebral angiography using transauricular access in a rabbit model: a new technique

BACKGROUND

Cerebral angiography in a rabbit model is widely used in the field of interventional radiology. Conventionally, the femoral artery is used for cerebral angiography in radiology departments. However, angiographic studies require surgical cutdown of the femoral artery, which is technically difficult.

PURPOSE

To evaluate a new cerebral angiography technique involving a transauricular approach in a rabbit model.

MATERIAL AND METHODS

In each of 10 rabbits, central auricular arteries were punctured in the right or left ear with a 20-gauge i.v. catheter. A microcatheter (2.0 F) with a 0.016-inch guide wire was introduced through the i.v. catheter and advanced to the aortic arch. The microcatheter and guide wire were advanced selectively into cerebral arteries and angiography was performed.

RESULTS

Central auricular arteries were successfully punctured with 20-gauge i.v. catheters. After approaching the aortic arch, microcatheter tips and guide wires were advanced manually to cerebral arteries on both sides. Difficulties in selecting the carotid arteries were resolved by using a looping technique within the cardiac chamber. Microcatheter loops within the cardiac chamber disappeared or remained during artery superselection.

CONCLUSION

Transauricular cerebral angiography appears to be a feasible technique for brain or carotid intervention studies in rabbits. In addition, vertebral angiography using a transauricular approach is possible using the looping technique. Selection of carotid or vertebral arteries on each side was not difficult when the microcatheter and guide wire were looped within the cardiac chamber. The ear chosen for the initial puncture does not appear to be important.

Ablation plus Transarterial Embolic Therapy for Hepatocellular Carcinoma Larger than 3 cm: Science, Evidence, and Future Directions

Thermal ablation is widely regarded as definitive therapy for early-stage hepatocellular carcinoma, but its efficacy decreases in tumors greater than 3 cm. Extensive clinical studies have supported improved outcomes provided through combining transarterial embolic therapy with ablation in the treatment of larger tumors. This article will provide a survey of the science and data for combination therapy in both thermal and nonthermal ablation modalities, as well as describe emerging applications.

Molecular Imaging of Extracellular Tumor pH to Reveal Effects of Locoregional Therapy on Liver Cancer Microenvironment

PURPOSE

To establish magnetic resonance (MR)-based molecular imaging paradigms for the noninvasive monitoring of extracellular pH (pH_e) as a functional surrogate biomarker for metabolic changes induced by locoregional therapy of liver cancer.

EXPERIMENTAL DESIGN

Thirty-two VX2 tumor-bearing New Zealand white rabbits underwent longitudinal imaging on clinical 3T-MRI and CT scanners before and up to 2 weeks after complete conventional transarterial chemoembolization (cTACE) using ethiodized oil (lipiodol) and doxorubicin. MR-spectroscopic imaging (MRSI) was employed for pH_e mapping. Multiparametric MRI and CT were performed to quantify tumor enhancement, diffusion, and lipiodol coverage of the tumor posttherapy. In addition, incomplete cTACE with reduced chemoembolic doses was applied to mimic undertreatment and exploit pH_e mapping to detect viable tumor residuals. Imaging findings were correlated with histopathologic markers indicative of metabolic state (HIF-1α, GLUT-1, and LAMP-2) and viability (proliferating cell nuclear antigen and terminal deoxynucleotidyl-transferase dUTP nick-end labeling).

RESULTS

Untreated VX2 tumors demonstrated a significantly lower pH_e (6.80 ± 0.09) than liver parenchyma (7.19 ± 0.03, P < 0.001). Upregulation of HIF-1α, GLUT-1, and LAMP-2 confirmed a hyperglycolytic tumor phenotype and acidosis. A gradual tumor pH_e increase toward normalization similar to parenchyma was revealed within 2 weeks after complete cTACE, which correlated with decreasing detectability of metabolic markers. In contrast, pH_e mapping after incomplete cTACE indicated both acidic viable residuals and increased tumor pH_e of treated regions. Multimodal imaging revealed durable tumor devascularization immediately after complete cTACE, gradually increasing necrosis, and sustained lipiodol coverage of the tumor.

CONCLUSIONS

MRSI-based pH_e mapping can serve as a longitudinal monitoring tool for viable tumors. As most liver tumors are hyperglycolytic creating microenvironmental acidosis, therapy-induced normalization of tumor pH_e may be used as a functional biomarker for positive therapeutic outcome.

Combination transarterial chemoembolization and microwave ablation improves local tumor control for 3- to 5-cm hepatocellular carcinoma when compared with transarterial chemoembolization alone

PURPOSE

To compare transarterial chemoembolization (TACE) monotherapy to combination TACE and microwave ablation (MWA) for local control of 3- to 5-cm hepatocellular carcinoma (HCC).

METHODS

Patients with HCC between 3 and 5 cm treated with TACE monotherapy or combination TACE + MWA at a single institution between 2007 and 2016 were retrospectively reviewed. Twenty-four HCCs (median diameter 3.8 cm) in 16 patients (13 males; median age 64 years) were treated using TACE monotherapy. Combination TACE + MWA was used to treat 23 HCCs (median diameter 4.2 cm) in 22 patients (18 males; median age 61 years). Microwave ablation was performed at a target time of two weeks following TACE. Individual tumors were followed by serial contrast-enhanced CT or MR. Response to treatment was evaluated on a tumor-by-tumor basis using mRECIST criteria with the primary outcome being local tumor progression (LTP). Data were analyzed using Fisher's exact test for categorical variables and Wilcoxon rank sum test for continuous variables. Time to LTP was estimated with the Kaplan-Meier method.

RESULTS

Relative to TACE monotherapy, TACE + MWA provided a trend toward both a lower rate of LTP (34.8% vs. 62.5%, p = 0.11) and a higher complete response rate (65.2% vs. 37.5%; p = 0.12). Time to LTP (22.3 months vs. 4.2 months; p = 0.001) was significantly longer in the TACE + MWA group compared to TACE monotherapy.

CONCLUSIONS

Combination therapy with TACE and microwave ablation improves local control and increases time to LTP for 3-5 cm HCC.

Evaluation of the Heat Sink Effect After Transarterial Embolization When Performed in Combination with Thermal Ablation of the Liver in a Rabbit Model

PURPOSE

To assess the contribution of the heat sink effect when combining thermal ablation with transarterial embolization (TAE).

MATERIALS AND METHODS

Radiofrequency ablation (RFA) or microwave ablation (MWA) were performed in the liver of non-tumor bearing rabbits. Three perfusion groups were used: rabbits that were killed then immediately ablated (non-perfused liver group to simulate embolized tumor with no heat sink), rabbits that underwent hepatic TAE followed by ablation (embolized liver group), and rabbits that underwent ablation while alive (normally perfused liver control group). For each perfusion group, 8 RFAs and 8 MWAs were performed. Probes were inserted using ultrasound guidance to avoid areas with major blood vessels. During ablation, temperatures were obtained from a thermocouple located 1 cm away from the ablation probe to assess heat conduction. With MWA, temperatures were also measured from the antennae tip.

RESULTS

For RFA, embolization of normal liver did not increase temperature conduction when compared to the control group. However, temperature conduction was significantly increased in the non-perfused group (simulating embolized tumor) compared to controls (p = 0.007). For MWA, neither embolization nor non-perfusion increased temperature conduction compared to controls. With MWA, the probe tip temperature was significantly higher in the non-perfused group compared to the control and embolized group.

CONCLUSIONS

In non-perfused tissue simulating tumor, RFA demonstrated modest enhancement of temperature conduction, whereas MWA did not. Embolization of normal liver did not affect RFA or MWA. Findings suggest that heat sink mitigation plays a limited role with combination embolization-ablation therapies, albeit more with RFA than MWA.

Percutaneous Ablation for Hepatocellular Carcinoma

OBJECTIVE

The purpose of this article is to discuss the use, comparative efficacy, and general technical considerations of percutaneous ablation, alone or in combination with other therapies, for the treatment of hepatocellular carcinoma (HCC).

CONCLUSION

Percutaneous ablation is a mainstay treatment for early-stage HCC, offering survival comparable to that of surgical resection for small lesions. It can act as a primary curative therapy or bridge therapy for patients waiting to undergo liver transplant. New ablation modalities and combining tumor ablation with other therapies, such as transarterial chemoembolization, can improve clinical outcomes and allow treatment of larger lesions. Combining thermal ablation with systemic chemotherapy, including immunotherapy, is an area of future development.

Histological Comparison of Kidney Tissue Following Radioembolization with Yttrium-90 Resin Microspheres and Embolization with Bland Microspheres

BACKGROUND

Intra-arterial brachytherapy with yttrium-90 (⁹⁰Y) resin microspheres (radioembolization) is a procedure to selectively deliver high-dose radiation to tumors. The purpose of this research was to compare the radioembolic effect of ⁹⁰Y-radioembolization versus the embolic effect of bland microspheres in the porcine kidney model.

METHODS

In each of six pigs, ~25-33 % of the kidney volume was embolized with ⁹⁰Y resin microspheres and an equivalent number of bland microspheres in the contralateral kidney. Kidney volume was estimated visually from contrast-enhanced fluoroscopy imaging. Morphologic and histologic analysis was performed 8-9 weeks after the procedure to assess the locations of the microspheres and extent of tissue necrosis from ⁹⁰Y-radioembolization and bland embolization. A semi-quantified evaluation of the non-acute peri-particle and perivascular tissue reaction was conducted. All guidelines for the care and use of animals were followed.

RESULTS

Kidneys embolized with ⁹⁰Y-radioembolization decreased in mass by 30-70 % versus the contralateral kidney embolized with bland microspheres. These kidneys showed significant necrosis/fibrosis, avascularization, and glomerular atrophy in the immediate vicinity of the ⁹⁰Y resin microspheres. By contrast, glomerular changes were not observed, even with clusters of bland microspheres in afferent arterioles. Evidence of a foreign body reaction was recorded in some kidneys with bland microspheres, and subcapsular scarring/infarction only with the highest load (4.96 × 10⁶) of bland microspheres.

CONCLUSION

This study showed that radioembolization with ⁹⁰Y resin microspheres produces localized necrosis/fibrosis and loss of kidney mass in a porcine kidney model. This result supports the study of ⁹⁰Y resin microspheres for the localized treatment of kidney tumors.

Novel implications in the treatment of hepatocellular carcinoma

Worldwide hepatocellular carcinoma remains one of the leading causes of cancer-related death, associated with a poor prognosis due to late diagnosis in the majority of cases. Physicians at care are frequently confronted with patients who are ineligible for curative treatment such as liver resection, transplantation or radiofrequency ablation. Besides established palliative locoregional therapies, such as ablation or chemoembolization, new treatment options, such as microwave ablation, drug-eluting bead transarterial chemoembolization or selective internal radiation therapy, are emerging; however, data from randomized controlled trials are still lacking. In order to achieve optimal tumor control, patients should receive tailored treatment concepts, considering their tumor burden, liver function and performance status, instead of strictly assigning patients to treatment modalities following algorithms that may be partly very restrictive. Palliative locoregional pretreatment might facilitate downstaging to ensure later curative resection or transplantation. In addition, the combined utilization of different locoregional treatment options or systemic co-treatment has been the subject of several trials. In cases where local tumor control cannot be achieved, or in the scenario of extrahepatic spread, sorafenib remains the only approved systemic therapy option. Alternative targeted therapies, such as immune checkpoint inhibitors have shown encouraging preliminary results, while data from phase III studies are pending.

Hepatic Tumor Ablation

Tumor ablation is a safe and effective treatment available in the multidisciplinary care of the surgical oncology patient. The role of ablation is well established in the treatment of hepatocellular carcinoma and is becoming more accepted in the treatment of various malignancies metastatic to the liver, in particular colorectal cancer. Understanding the underlying technology, achieving appropriate applicator placement, using maximum energy delivery to create margins, and performing necessary adjunctive maneuvers are all required for successful tumor ablation.

Imaging Intratumoral Nanoparticle Uptake After Combining Nanoembolization with Various Ablative Therapies in Hepatic VX2 Rabbit Tumors

Combining image-guided therapy techniques for the treatment of liver cancers is a strategy that is being used to improve local tumor control rates. Here, we evaluate the intratumoral uptake of nanoparticles used in combination with radiofrequency ablation (RFA), irreversible electroporation (IRE), or laser induced thermal therapy (LITT). Eight rabbits with VX2 tumor in the liver underwent one of four treatments: (i) nanoembolization (NE) with radiolabeled, hollow gold nanoparticles loaded with doxorubicin (⁶⁴Cu-PEG-HAuNS-DOX); (ii) NE + RFA; (iii) NE + IRE; (iv) NE +LITT. Positron emission tomography/computed tomography (PET/CT) imaging was obtained 1-hr or 18-hrs after intervention. Tissue samples were collected for autoradiography and transmission electron microscopy (TEM) analysis. PET/CT imaging at 1-hr showed focal deposition of oil and nanoparticles in the tumor only after NE+ RFA but at 18-hrs, all animals had focal accumulation of oil and nanoparticles in the tumor region. Autoradiograph analysis demonstrated nanoparticle deposition in the tumor and in the ablated tissues adjacent to the tumor when NE was combined with ablation. TEM results showed the intracellular uptake of nanoparticles in tumor only after NE + IRE. Nanoparticles demonstrated a structural change, suggesting direct interaction, potentially leading to drug release, only after NE + LITT. The findings demonstrate that a combined NE and ablation treatment technique for liver tumors is feasible, resulting in deposition of nanoparticles in and around the tumor. Depending on the ablative energy applied, different effects are seen on nanoparticle localization and structure. These effects should be considered when designing nanoparticles for use in combination with ablation technologies.

Liver Ablation: Best Practice

Tumor ablation in the liver has evolved to become a well-accepted tool in the management of increasing complex oncologic patients. At present, percutaneous ablation is considered first-line therapy for very early and early hepatocellular carcinoma and second-line therapy for colorectal carcinoma liver metastasis. Because thermal ablation is a treatment option for other primary and secondary liver tumors, an understanding of the underlying tumor biology is important when weighing the potential benefits of ablation. This article reviews ablation modalities, indications, patient selection, and imaging surveillance, and emphasizes technique-specific considerations for the performance of percutaneous ablation.

Low-frequency and low-intensity ultrasound-mediated microvessel disruption enhance the effects of radiofrequency ablation on prostate cancer xenografts in nude mice

The aim of the present study was to examine the impact of low-frequency, low-intensity ultrasound (US)-stimulated microbubbles (USMB) on radiofrequency ablation (RFA) in the treatment of nude mice with human prostate cancer xenografts. The tumor‑bearing nude mice were divided into three groups: The USMB+RFA group was treated with USMB immediately followed by RFA, the RFA group was treated with RFA alone, and the control group remained untreated. The animals underwent enhanced US to calculate the tumor volumes, ablation volumes and ablation rates. Subsequently, the tumors were excised for hematoxylin and eosin staining, to identify necrosis in the tumors following the treatments, and immunohistochemical staining, to analyze the apoptotic index (AI), proliferative index (PI) and microvessel density (MVD) at 1, 4 and 7 days post-treatment. Each group contained five mice at each time‑point. Necrosis was apparent in the center of the tumors in the treatment groups. Ablation lesion volumes of the USMB+RFA group were larger than those in the RFA group at 1 and 4 days post‑treatment (P=0.002 and P=0.022, respectively), and the ablation rates of the USMB+RFA group were significantly higher, compared with the RFA group at the three time‑points (all P<0.001). There were fewer apoptotic cells and more proliferative cells in the RFA group, compared with the control group 1,4 and 7 days post‑treatment (all P<0.05). The AI of the USMB+RFA group was higher than that of the control group and lower than that of the RFA group 1 day post-treatment (P=0.034 and P=0.016, respectively). The PI of the USMB+RFA group was lower than that of the control group and higher than that of the RFA group 4 and 7 days post-treatment (all P<0.05). No significant differences were observed in MVD among the three groups throughout the experiment. In conclusion, exposure to USMB prior to RFA produced larger volumes of ablation, compared with treatment with RFA alone, and increased AI and reduced PI in the residual carcinoma cells induced by RFA.

Transcatheter embolization therapy in liver cancer: an update of clinical evidences

Transarterial chemoembolization (TACE) is a form of intra-arterial catheter-based chemotherapy that selectively delivers high doses of cytotoxic drug to the tumor bed combining with the effect of ischemic necrosis induced by arterial embolization. Chemoembolization and radioembolization are at the core of the treatment of liver hepatocellular carcinoma (HCC) patients who cannot receive potentially curative therapies such as transplantation, resection or percutaneous ablation. TACE for liver cancer has been proven to be useful in local tumor control, to prevent tumor progression, prolong patients' life and control patient symptoms. Recent evidence showed in patients with single-nodule HCC of 3 cm or smaller without vascular invasion, the 5-year overall survival (OS) with TACE was similar to that with hepatic resection and radiofrequency ablation. Although being used for decades, Lipiodol(®) (Lipiodol(®) Ultra Fluid(®), Guerbet, France) remains important as a tumor-seeking and radio-opaque drug delivery vector in interventional oncology. There have been efforts to improve the delivery of chemotherapeutic agents to tumors. Drug-eluting bead (DEB) is a relatively novel drug delivery embolization system which allows for fixed dosing and the ability to release the anticancer agents in a sustained manner. Three DEBs are available, i.e., Tandem(®) (CeloNova Biosciences Inc., USA), DC-Beads(®) (BTG, UK) and HepaSphere(®) (BioSphere Medical, Inc., USA). Transarterial radioembolization (TARE) technique has been developed, and proven to be efficient and safe in advanced liver cancers and those with vascular complications. Two types of radioembolization microspheres are available i.e., SIR-Spheres(®) (Sirtex Medical Limited, Australia) and TheraSphere(®) (BTG, UK). This review describes the basic procedure of TACE, properties and efficacy of some chemoembolization systems and radioembolization agents which are commercially available and/or currently under clinical evaluation. The key clinical trials of transcatheter arterial therapy for liver cancer are summarized.

Radiofrequency ablation combined with transcatheter therapy in rabbit VX2 liver tumors: effects and histopathological characteristics

BACKGROUND

Transarterial chemoembolization (TACE) combined with radiofrequency ablation (RFA) treatment (TACE-RFA) has been confirmed superior to TACE or RFA alone in animal liver tumors. TACE before RFA was shown to increase hepatocellular damage. Further optimization of the combination strategy for transcatheter arterial embolization (TAE) or TACE combined with RFA is warranted.

PURPOSE

To determine the optimal strategy for radiofrequency ablation combined with transcatheter therapies in VX2 liver tumors in a rabbit model.

MATERIAL AND METHODS

Twenty-four Japanese White rabbits with VX2 liver tumors were randomly divided into four groups: TACE-RFA (TACE-RFA group), transcatheter arterial embolization (TAE) combined with RFA treatment (TAE-RFA group), RFA only group, and TACE only group. Blood samples were collected 1 day before the operation and at 3 and 7 days postoperatively. Seven days after the operation, maximal diameters of coagulation or infarcted zones in the gross specimens, CT images, histopathological characteristics, tumor necrotic rate, and growth rate were compared.

RESULTS

Significantly larger mean long-axis (P < 0.05) and short-axis (P < 0.05) diameters of coagulation and infarction were observed in the TACE-RFA group compared with the TAE-RFA, RFA, and TACE groups on day 7; and the TAE-RFA group showed a significant (P < 0.05) increase versus the RFA and TACE groups on day 7. There were no significant differences in tumor growth rate (109.3 ± 37.5 vs. 119.0 ± 43.1%, P = 0.45) and necrotic rate (89.5 ± 12.0 vs. 83.5 ± 9.3%, P = 0.73) between the TACE-RFA and TAE-RFA groups. TACE-RFA was more effective for achieving tumor destruction than the other treatment strategies, but led to increased rabbits discomfort and more severe liver dysfunction compared with TAE-RFA.

CONCLUSION

TAE-RFA appears to be a beneficial therapeutic modality for treating VX2 liver tumors in a rabbit model.

Technical and practical considerations for device selection in locoregional ablative therapy

Percutaneous ablation therapy is an essential component of contemporary interventional oncologic therapy of primary and secondary malignancies. The growing armamentarium of available ablation technologies calls for thorough understanding of the different ablation modalities to optimize device selection in individual clinical settings. The goal of the current article is to provide direction on ablative device selection by reviewing device mechanisms of action, advantages and disadvantages, and practical considerations in real-life case scenarios.

Combining locoregional therapies in the treatment of hepatocellular carcinoma

In an effort to promote more durable local control of larger lesions, thermal ablation has been combined with chemical ablative techniques and with vaso-occlusive procedures such as chemoembolization and bland embolization in an effort to mitigate the limitations inherent in the use of any single treatment for hepatocellular carcinoma (HCC) >3 cm. The heat-sink effect is the underlying principle for combining vaso-occlusive therapies with ablative techniques. Combination therapies do present viable options for abrogating tumor progression and potentially downsizing tumors to facilitate transplant. We discuss the two most commonly used combination locoregional therapies by the interventionalist and the evidence defining the best techniques in practice.

Colorectal cancer metastasis: the DNA repair inhibitor Dbait increases sensitivity to hyperthermia and improves efficacy of radiofrequency ablation

PURPOSE

To assess the usefulness of combining hyperthermia with a DNA repair inhibitor (double-strand break bait [Dbait]) and its potential application to radiofrequency ablation (RFA) in a preclinical model of human colorectal cancer.

MATERIALS AND METHODS

The local ethics committee of animal experimentation approved all investigations. First, the relevance was assessed by studying the survival of four human colorectal adenocarcinoma cell cultures after 1 hour of hyperthermia at 41°C or 43°C with or without Dbait. Human colon adenocarcinoma cells (HT-29) were grafted subcutaneously into nude mice (n = 111). When tumors reached approximately 500 mm(3), mice were treated with Dbait alone (n = 20), sublethal RFA (n = 21), three different Dbait schemes and sublethal RFA (n = 52), or a sham treatment (n = 18). RFA was performed to ablate the tumor center alone. To elucidate antitumor mechanisms, 39 mice were sacrificed for blinded pathologic analysis, including assessment of DNA damage, cell proliferation, and tumor necrosis. Others were monitored for tumor growth and survival. Analyses of variance and log-rank tests were used to evaluate differences.

RESULTS

When associated with mild hyperthermia, Dbait induced cytotoxicity in all tested colon cancer cell lines. Sublethal RFA or Dbait treatment alone moderately improved survival (median, 40 days vs 28 days for control; P = .0005) but combination treatment significantly improved survival (median, 84 days vs 40 days for RFA alone, P = .0004), with approximately half of the animals showing complete tumor responses. Pathologic studies showed that the Dbait and RFA combination strongly enhances DNA damage and coagulation areas in tumors.

CONCLUSION

Combining Dbait with RFA sensitizes the tumor periphery to mild hyperthermia and increases RFA antitumor efficacy.

Novel approaches to treatment of hepatocellular carcinoma and hepatic metastases using thermal ablation and thermosensitive liposomes

Because of the limitations of surgical resection, thermal ablation is commonly used for the treatment of hepatocellular carcinoma and liver metastases. Current methods of ablation can result in marginal recurrences of larger lesions and in tumors located near large vessels. This review presents a novel approach for extending treatment out to the margins where temperatures do not provide complete treatment with ablation alone, by combining thermal ablation with drug-loaded thermosensitive liposomes. A history of the development of thermosensitive liposomes is presented. Clinical trials have shown that the combination of radiofrequency ablation and doxorubicin-loaded thermosensitive liposomes is a promising treatment.

Evaluation of ghost cell survival in the area of radiofrequency ablation

Background and Aim

Researchers have demonstrated dead cells in radiofrequency ablation (RFA) lesions that have morphological similarities to viable tumor cells and are thus referred to as ghost cells. However, studies on how long ghost cells persist have not been systematically performed.

Methods

A tumor model was established by implanting VX2 tumor tissue into the livers of 48 New Zealand rabbits. Two weeks later, these tumors were eliminated with RFA. The lesions were resected at 0 weeks, 1 week, 2 weeks, 4 weeks, 8 weeks, or 12 weeks after treatment, and samples were stained either with hematoxylin and eosin (HE) or nicotinamide adenine dinucleotide (NADH). The presence of the cells and the morphological changes that they underwent were examined by light microscopy.

Results

Four weeks after RFA, there were no obvious morphological changes observed in HE-stained ghost cells, and NADH staining revealed no viable cells. Eight weeks after RFA, the cell structure became indistinct. Twelve weeks after RFA, ghost cells were no longer present.

Conclusions

The morphological characteristics of ghost cells are maintained for at least 4 weeks, during which time HE staining cannot be used to differentiate ghost cells from residual tumor cells. NADH staining for cell viability is necessary to differentiate residual tumor cells from ghost cells. This evidence adds to our understanding of the mechanisms of RFA when used on solid tumors.

Unresectable lung malignancy: combination therapy with segmental pulmonary arterial chemoembolization with drug-eluting microspheres and radiofrequency ablation in 17 patients

PURPOSE

To evaluate the feasibility, safety, and effectiveness of combining segmental pulmonary arterial chemoembolization (SPACE) and percutaneous radiofrequency (RF) ablation in patients with unresectable lung neoplasms or patients with resectable neoplasms who refused surgery and to compare the local tumor progression (LTP) rate with that in previous studies of RF ablation alone.

MATERIALS AND METHODS

After institutional review board approval and informed consent, 17 patients with primary and metastatic lung cancer were enrolled in this prospective study. Between January 2008 and February 2011, 20 nodules (median diameter, 3.0 cm; range, 2.0-5.0 cm) were treated during 19 sessions. Antineoplastic agents loaded on 50-100-µm microspheres were selectively infused into specific pulmonary arteries. Percutaneous computed tomography (CT)-guided RF ablation of lung nodules was performed 48 hours after SPACE. Follow-up consisted of enhanced CT 48 hours after combination treatment was completed, after 30 days, and every 3 months thereafter. Fluorine 18 fluorodeoxyglucose positron emission tomography was performed 3 months after combination therapy and then every 6 months. The t test was used to compare groups.

RESULTS

Technical success was achieved in 100% of cases. Ventilation-lung single photon emission computed tomography showed a wide area without ventilation in the lung parenchyma treated with SPACE. The LTP rate was 21% (three of 14 nodules) in 3-5-cm-diameter tumors and 0% (zero of six nodules) in tumors of 3 cm or smaller in diameter. Complete response was achieved in 65% (11 of 17) of patients at minimum follow-up of 6 months. Overall, treatment was well tolerated. Major complications were pneumothorax in five of 19 sessions (26%) and one bronchopleural fistula (one of 19, 5%). No treatment-related changes in general lung function were noted.

CONCLUSION

Combination therapy with RF ablation after SPACE to treat unresectable lung tumors is technically feasible, safe, and effective and may represent an advantage over RF ablation alone.

Superselective particle embolization enhances efficacy of radiofrequency ablation: effects of particle size and sequence of action

PURPOSE

To evaluate the effects of particle size and course of action of superselective bland transcatheter arterial embolization (TAE) on the efficacy of radiofrequency ablation (RFA).

METHODS

Twenty pigs were divided into five groups: group 1a, 40-μm bland TAE before RFA; group 1b, 40-μm bland TAE after RFA; group 2a, 250-μm bland TAE before RFA; group 2b, 250-μm bland TAE after RFA and group 3, RFA alone. A total of 40 treatments were performed with a combined CT and angiography system. The sizes of the treated zones were measured from contrast-enhanced CTs on days 1 and 28. Animals were humanely killed, and the treated zones were examined pathologically.

RESULTS

There were no complications during procedures and follow-up. The short-axis diameter of the ablation zone in group 1a (mean ± standard deviation, 3.19 ± 0.39 cm) was significantly larger than in group 1b (2.44 ± 0.52 cm; P = 0.021), group 2a (2.51 ± 0.32 cm; P = 0.048), group 2b (2.19 ± 0.44 cm; P = 0.02), and group 3 (1.91 ± 0.55 cm; P < 0.001). The greatest volume of ablation was achieved by performing embolization with 40-μm particles before RFA (group 1a; 20.97 ± 9.65 cm(3)). At histology, 40-μm microspheres were observed to occlude smaller and more distal arteries than 250-μm microspheres.

CONCLUSION

Bland TAE is more effective before RFA than postablation embolization. The use of very small 40-μm microspheres enhances the efficacy of RFA more than the use of larger particles.

Radiofrequency ablation combined with transcatheter arterial embolisation in rabbit liver: investigation of the ablation zone according to the time interval between the two therapies

OBJECTIVES

This study was designed to evaluate the extent of the radiofrequency ablation zone in relation to the time interval between transcatheter arterial embolisation (TAE) and radiofrequency ablation (RFA) and, ultimately, to determine the optimal strategy of combining these two therapies for hepatocellular carcinoma.

METHODS

15 rabbits were evenly divided into three groups: Group A was treated with RFA alone; Group B was treated with TAE immediately followed by RFA; and Group C was treated with TAE followed by RFA 5 days later. All animals underwent perfusion CT (PCT) scans immediately after RFA. Serum liver transaminases were measured to evaluate acute liver damage. Animals were euthanised for pathological analysis of ablated tissues 10 days after RFA. Non-parametric analyses were conducted to compare PCT indices, the RFA zone and liver transaminase levels among the three experimental groups.

RESULTS

Group B showed a significantly larger ablation zone than the other two groups. Arterial liver perfusion and hepatic perfusion index represented well the perfusion decrease after TAE on PCT. Although Group B showed the most elevated liver transaminase levels at 1 day post RFA, the enzymes decreased to levels that were not different from the other groups at 10 days post-RFA.

CONCLUSIONS

When combined TAE and RFA therapy is considered, TAE should be followed by RFA as quickly as possible, as it can be performed safely without serious hepatic deterioration, despite the short interval between the two procedures.

Comparison between transauricular and transfemoral arterial access for hepatic artery angiography in a rabbit model

PURPOSE

To evaluate the feasibility of transauricular arterial access and compare the procedure time needed for hepatic artery angiography via transfemoral versus transauricular arterial access in a rabbit model.

MATERIALS AND METHODS

This study was approved by the research animal care and use committee. Twenty rabbits were divided into transfemoral (n = 10) and transauricular access groups (n = 10). The procedure consisted of shaving the hair, obtaining intraarterial access, performing hepatic artery angiography, and repairing the access site. A Mann-Whitney U test was used to compare the two groups in terms of the total procedure time and the time needed for each step.

RESULTS

Hepatic artery angiography was technically feasible in all animals in both groups. The time required for shaving was 55 seconds ± 9.9 in the transfemoral access group; shaving was unnecessary in the transauricular access group. The times needed to obtain intraarterial access, perform hepatic artery angiography, repair the access site, and perform the entire procedure in the transfemoral and transauricular access groups were as follows: 503.3 s ± 211.8 and 97 s ± 83.3 (P < .001), 229.6 s ± 90 and 310.7 s ± 211 (P = .705), 305.5 s ± 80.6 and 90 s ± 0 (P < .001), and 1,038 s ± 265.9 and 497.7 s ± 256.9 (P = 0.001), respectively.

CONCLUSIONS

Hepatic artery angiography is technically feasible via transauricular arterial access. The major advantages of transauricular arterial access versus transfemoral arterial access include a procedure time reduced by the omission of shaving and surgical cutdown.

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.

Combination radiofrequency ablation and intravenous radiolabeled liposomal Doxorubicin: imaging and quantification of increased drug delivery to tumors

PURPOSE

To identify, with noninvasive imaging, the zone of radiopharmaceutical uptake after combination therapy with radiofrequency (RF) ablation and intravenous administration of technetium 99m ((99m)Tc) liposomal doxorubicin in a small-animal tumor model, and to quantify and correlate the uptake by using imaging and tissue counting of intratumoral doxorubicin accumulation.

MATERIALS AND METHODS

This study was approved by the animal care committee. Two phases of animal experiments were performed. In the first experiment, a single human head-and-neck squamous cell carcinoma tumor was grown in each of 10 male nude rats. Seven of these animals were treated with intravenous (99m)Tc-liposomal doxorubicin followed by RF tumor ablation at a mean temperature of 70 degrees C + or - 2 for 5 minutes, and three were treated with intravenous (99m)Tc-liposomal doxorubicin only. Combination single photon emission computed tomography-computed tomography (SPECT/CT) was performed at 15 minutes, 4 hours, and 20 hours after therapy. In the second experiment, two tumors each were grown in 11 rats, but only one of the tumors was ablated after intravenous administration of (99m)Tc-liposomal doxorubicin. SPECT/CT and planar scintigraphy were performed at the same posttreatment intervals applied in the first experiment, with additional planar imaging performed at 44 hours. After imaging, tissue counting in the excised tumors was performed. Radiotracer uptake, as determined with imaging and tissue counting, was quantified and compared. In a subset of three animals, intratumoral doxorubicin accumulation was determined with fluorimetry and correlated with the imaging and tissue-counting data.

RESULTS

At both SPECT/CT and planar scintigraphy, increased uptake of (99m)Tc-liposomal doxorubicin was visibly apparent in the ablated tumors. Results of quantitative analysis with both imaging and tissue counting confirmed significantly greater uptake in the RF ablation-treated tumors (P < .001). Intratumoral doxorubicin accumulation correlated closely with imaging (r = 0.9185-0.9871) and tissue-counting (r = 0.995) results.

CONCLUSION

Study results show that increased delivery of intravenous liposomal doxorubicin to tumors combined with RF ablation can be depicted and quantified with noninvasive imaging.

Development of a VX2 pancreatic cancer model in rabbits: a pilot study

PURPOSE

An animal model of pancreatic cancer that is large enough to permit imaging and catheterization would be desirable for interventional radiologists to develop novel therapies for pancreatic cancer. The purpose of this study was to test the hypothesis that the VX2 rabbit model of pancreatic cancer could be developed as a suitable platform to test future interventional therapies.

MATERIALS AND METHODS

The authors implanted and grew three pancreatic VX2 tumors per rabbit in six rabbits. Magnetic resonance (MR) imaging was performed at 2 weeks to confirm tumor growth. At 3 weeks, the authors selectively catheterized the gastroduodenal artery under guidance of x-ray digital subtraction angiography (DSA). T2-weighted anatomic imaging, diffusion-weighted MR imaging, and transcatheter intraarterial perfusion (TRIP) MR imaging were then performed. After imaging, tumors were confirmed at necropsy and histopathologically. Tumor sizes at 2 and 3 weeks were compared with a paired t test (P = .05).

RESULTS

VX2 pancreatic tumors were grown in all six rabbits. The difference between tumor sizes at 2 and 3 weeks (1.29 cm +/- 0.39 vs 1.91 cm +/- 0.50, respectively) was significant (P < .001). All tumors were confirmed to be located within pancreatic tissue via histopathologic analysis. DSA and TRIP MR imaging were successful in five rabbits. Diffusion-weighted and anatomic MR imaging were successful in all six rabbits.

CONCLUSIONS

The VX2 rabbit model of pancreatic cancer is feasible, as verified by imaging and pathologic correlation, and may be a suitable platform to test future interventional therapies.