Microwave Ablation with Percutaneous Approach for the Treatment of Pancreatic Adenocarcinoma

Microwave ablation on ex vivo porcine pancreas: The influence of ablation parameters on ablation results and fat liquefaction

The pancreas is adjacent to critical organs; excessive microwave ablation (MWA) can result in serious complications. The purpose of this paper is to provide the reference data of pancreas MWA for clinicians, analyze the ablation outcomes under different ablation parameters, and determine the critical temperature of pancreatic surface fat liquefaction outflow. Combinations of two power levels (30 W and 55 W), three antenna diameters (1.3 mm, 1.6 mm, and 1.9 mm), and three ablation times (1 min, 1.5 min, and 2 min) were applied to an ex vivo pig pancreas. Temperature measurements were taken at four thermocouple points. The center point is located 5 mm horizontally from the antenna slot, with a temperature measurement point located 5 mm above, below, and to the right of the center point. Main effect analysis and variance analysis were used to quantify the influences of each factor on the ablation outcomes. At 30 W, the antenna diameter contributing the most at 48.5%. At 30 W-1.3 mm-1 min, the spherical index (1.41) is closest to 1. At 55 W, the coagulation zone size was almost only affected by the ablation time, with a contribution rate of 28.7%, the temperature at point C exceeds point B. On the surface of the ex vivo porcine pancreas, the fat outflow temperature was 54ã. Ablation combinations with low power, short duration, and small antenna diameter results in a more nearly spherical coagulation zone. When performing MWA on the pancreas, it is advisable to avoid areas with higher fat content, while keeping the pancreatic surface temperature below 54°C.

Advancements in Microwave Ablation Techniques for Managing Pancreatic Lesions

Thermal ablation, including microwave ablation, has become increasingly important in the management of many solid tumors, including primary and metastatic tumors of the liver, kidney, and lung. However, its adoption to treat pancreatic lesions has been slowed due to concerns about potential adverse events. The success of radiofrequency ablation (RFA) in inoperable pancreatic cancers paved the way for its use in pancreatic neuroendocrine tumors and pancreatic cystic neoplasms (PCLs). In the last decade, other thermal ablation techniques, like microwave ablation, have emerged as alternatives to RFA. Microwaves, with frequencies ranging from 900 to 2450 MHz, generate heat by rapidly oscillating water molecules. Microwave ablation's advantage lies in its ability to achieve higher intra-lesion temperatures and uniform heating compared with RFA. Microwave ablation's application in pancreatic cancer and pancreatic neuroendocrine tumors has demonstrated promise with similar technical success to RFA. Yet, concern for peri-procedure complications, as well as a dearth of studies comparing RFA and microwave ablation, emphasize the need for further research. No studies have evaluated microwave ablation in PCLs. We herein review thermal ablation's potential to treat pancreatic lesions.

The underlying molecular mechanism of intratumoral radiofrequency hyperthermia-enhanced chemotherapy of pancreatic cancer

Background

To investigate the underlying molecular mechanisms of radiofrequency hyperthermia (RFH)-enhanced direct chemotherapy of pancreatic cancers.

Method

Rat ductal PaCa cell line DSL-6A/C1 and orthotopic pancreatic cancers of Lewis rats were divided into four study groups with various treatments: i) phosphate-buffered saline (PBS) as a control; ii) RFH alone; iii) intratumoral chemotherapy alone (gemcitabine); and (iv) combination therapy of gemcitabine plus intratumoral RFH at 42 ​°C for 30 ​min. In the in-vitro confirmation experiments, the viability and apoptosis of DSL-6A/C1 cells in each treatment group were evaluated using cell live/dead staining, flow cytometry, and Western blot. In the in vivo validation experiments, related proteins were evaluated by immunohistochemistry (IHC) staining of tumors.

Results

Of the in-vitro experiments, the lowest cell viability and more apoptotic cells were shown in the group with combination therapy compared to other treatments. Western blot data showed elevated Bax/Bcl-2, Caspase-3, and HSP70 expressions in DSL cells with combination therapy, compared to other treatments. Of the in vivo experiments, IHC staining detected the significantly increased expressions of HSP70, IL-1β, TNF-ɑ, Bax, and Caspase-3 in pancreatic cancer tissues of the animal group treated by combination therapy of gemcitabine with RFH.

Conclusion

Molecular imaging-guided interventional RFH can significantly enhance the chemotherapeutic effect on pancreatic cancers via potential molecular mechanisms of up-regulating Bax/caspase-3-dependent apoptosis pathways.

Role of radio-ablative technique for optimizing the survival of patients with locally advanced pancreatic adenocarcinoma (Review)

Pancreatic ductal adenocarcinoma (PDAC) is one of the most common and frequently diagnosed malignant tumor of the pancreas with few treatment options and poor life expectancy. Despite the advances in the surgical field, 40% of the patients are diagnosed with locally advanced disease which is not suitable for surgery. Radio-frequency ablation (RFA) has been described as a new ‘weapon’ in the multimodal treatment of PDAC, representing a cytoreductive procedure which must be completed with radiotherapy or chemo-radiotherapy. A systematic research was carried out utilizing the PubMed database in regards to this subject, to evaluate the role of RFA in PDAC management. Abstracts, letters-to-the-editor and non-English language manuscripts were excluded. The literature showed that RFA can be used in open and laparoscopic surgery but it is also feasible for endoscopic ultrasound (EUS-guided RFA) or percutaneous approach. Even though we found optimistic and encouraging reports on overall survival (OS), randomized studies are still required to corroborate these findings. Our review research underline that surgical resection remains the only radical treatment option, RFA being a safe and feasible technique reserved for unresectable, non-metastatic pancreatic tumors. Its combination with oncological treatment can improve the OS of these patients.

Neutralizing TGF-β promotes anti-tumor immunity of dendritic cells against pancreatic cancer by regulating T lymphocytes

Previous fundamental or clinical trials of dendritic cell (DC) vaccine against pancreatic ductal adenocarcinoma (PDAC) revealed the burgeoning neoadjuvant immunotherapy. Microarray studies indicated that multiple ingredients of the transfer growth factor beta (TGF-β) pathway were overexpressed in PDAC, which inhibited the intratumoral immune response. To explore whether the DC volume in tumor microenvironment contributes to the differentiation of T cell cohort and test the hypothesis that combining DC vaccine with TGF-β inhibitors will elevate the anti-tumor immune response, we managed to co-culture T cells in vitro with pancreatic cancer cells and DCs in different concentrations, and combine TGF-β blockage with DC vaccine therapy in a murine model of pancreatic cancer. In in vitro studies, we discovered that CD8⁺ T cytotoxic cell (Tc) presented a significant advantage and lower volume of CD4⁺ T helper cell (Th) existed with a certain elevated DC concentration (p < 0.05), associated with declined interleukin (IL)-10 and increased interferon (IFN)-γ, which suggested with the DC volume increasing, the enhancing immune effect may represent a great advantage in such a system (p < 0.05). When interfered with anti-TGF-β antibody or TGF-β cytokine, respectively, in the co-culture system, we found IFN-γ producing was extremely higher and T cell apoptosis relatively descent with TGF-β blockage (p < 0.05). The murine PDAC model demonstrated a survival advantage treated with anti-TGF-β antibody combined with DC vaccine when compared with monotherapy controls (p < 0.05). Therefore, these findings indicated that, through neutralizing TGF-β associated with DC vaccine, the anti-tumor immunity is highly elevated and this combinational therapy will provide an efficacious prospect.

Ultrawideband, Stable Normal and Cancer Skin Tissue Phantoms for Millimeter-Wave Skin Cancer Imaging

This work introduces new, stable, and broadband skin-equivalent semisolid phantoms for mimicking interactions of millimeter waves with the human skin and skin tumors. Realistic skin phantoms serve as an invaluable tool for exploring the feasibility of new technologies and improving design concepts related to millimeter-wave skin cancer detection methods. Normal and malignant skin tissues are separately mimicked by using appropriate mixtures of deionized water, oil, gelatin powder, formaldehyde, TX-150 (a gelling agent, widely referred to as "super stuff"), and detergent. The dielectric properties of the phantoms are characterized over the frequency band of 0.5-50 GHz using a slim-form open-ended coaxial probe in conjunction with a millimeter-wave vector network analyzer. The measured permittivity results show excellent match with ex vivo, fresh skin (both normal and malignant) permittivities determined in our prior work over the entire frequency range. This work results in the closest match among all phantoms reported in the literature to surrogate human skin tissues. The stability of dielectric properties over time is also investigated. The phantoms demonstrate long-term stability (up to 7 months was investigated). In addition, the penetration depth of millimeter waves into normal and malignant skin phantoms is calculated. It is determined that millimeter waves penetrate the human skin deep enough (0.6 mm on average at 50 GHz) to affect the majority of the epidermis and dermis skin structures.

The safety and efficacy of microwave ablation for the treatment of CRC pulmonary metastases

PURPOSE

Microwave ablation (MWA) is a recently developed thermal ablation technique that has been used for the treatment of different types of tumours. In the present study, we retrospectively evaluated the safety and efficacy of CT-guided percutaneous MWA for the treatment of colorectal cancer (CRC) pulmonary metastases.

MATERIALS AND METHODS

From June 2010 to June 2015, 48 unresectable lesions in 32 patients with CRC pulmonary metastases were subjected to CT-guided MWA. Imaging follow-up was with contrast-enhanced CT and 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT.

RESULTS

Oncologic imaging showed that 42 (87.5%) of the 48 lesions in the 32 patients were completely ablated. Needle track metastatic seeding was not found, and no patient deaths occurred within 30 d after ablation. The mean hospital stay was 3 d (range, 2-7 d). Pneumothorax was the most frequent complication and occurred in 6 (12.5%) of the 48 lesions. The median survival time was 31 months (95% CI: 15.4-46.6). The 1-, 2- and 3-year survival rates were 79.5%, 63.1% and 44.4%, respectively. Univariate Cox regression analysis showed that tumour size, disease-free interval (DFI) and number of tumours were significantly related to the overall survival time (p = .007, p = .022 and p = .030, respectively). Multivariate analysis showed that tumour size was an independent prognostic factor for survival (p = .017).

CONCLUSION

CT-guided percutaneous MWA is a safe and effective minimally invasive method for treating CRC pulmonary metastases.

Multi-modality imaging-monitored creation of rat orthotopic pancreatic head cancer with obstructive jaundice

Purpose

To investigate the feasibility of using multi-modality imaging to monitor the creation of rat models with orthotopic pancreatic head cancer with obstructive jaundice.

Results

27 of 52 rats (51.92%) developed pancreatic head cancer. The tumor formation rate was significantly higher in the animal group receiving bioluminescent tumor, compared to the group receiving non-bioluminescent donor tumors [78.1% (25/32 rats) vs 10.0% (2/20 rats), P = 0.0001]. Both ultrasound imaging and MRI clearly characterized the orthotopic tumors. Laboratory biochemistry test for those rats with obstructive jaundice showed elevated levels of bilirubin, aspartate transaminase (AST), alkaline phosphatase (ALT) and gamma-glutamyl transpeptidase (λ-GGT), compared with those rats without jaundice (P < 0.05). Correlative pathology confirmed that all tumors were ductal adenocarcinomas, and located in pancreatic head regions.

Materials and Methods

Rat pancreatic adenocarcinoma cells (DSL-6A/C1) were first transfected with lentivirus/mCherry-luciferase genes, and then subcutaneously implanted into flanks of donor immunocompetent Lewis rats, to create pancreatic tumor tissues. The tumor tissues from donor rats with either bioluminescence signal or without the signal were then transplanted into the pancreatic heads of 52 recipient Lewis rats. Bioluminescence optical and ultrasound imaging, as well as magnetic resonance imaging (MRI), were performed to follow up the tumor formation and growth in these tumor-transplanted rats. Physical examination and biochemistry test were used to discern the rats with obstructive jaundice. The rats were euthanized for subsequent histologic correlation and confirmation.

Conclusions

We successfully created a new rat model with orthotopic pancreatic head cancer, which can be accurately monitored and visualized by different imaging modalities.

Combination of microbubbles and diagnostic ultrasound at a high mechanical index for the synergistic microwave ablation of tumours

OBJECTIVES

To determine whether combining microbubbles (MBs) with diagnostic ultrasound (US) at a high mechanical index (MI) could enhance the microwave (MW) ablation of tumours.

MATERIALS AND METHODS

Five therapeutic MW adjuvant protocols were studied: MW, MW + US, MW + US + MB, MW + US + NS (saline) and MW + MB. In 30 normal rabbit livers, the synergistic effects were evaluated via temperature, necrosis volume and histology. In 90 VX2 rabbit hepatic tumours, residual cells in the peripheral ablated tumours were examined via immunohistochemical assay and tumour growth. Additional 40 VX2 hepatic tumours were evaluated for ablation safety via blood assay and weight and for survival to 105 days. Results were compared using analysis of variance.

RESULTS

Compared with the other protocols, the ablation volumes in normal rabbit livers were significantly larger using the MW + US + MB protocol (p < .001). The histological examination was consistent with more efficient ablation in that protocol. In detecting residual cells, the apoptotic index was higher, the proliferating index was lower (p < .05), tumour growth was significantly smaller (p < .001), and the rabbits of the MW + US + MB T-Group survived longer (p < .05) than those of the other groups. Additionally, no damage to the liver function or blood cells was found in any of the protocols after ablation (p < .05).

CONCLUSIONS

MBs in combination with diagnostic US at a high MI showed potential synergy in the MW ablation of tumours in rabbits.

CT Findings of Patients Treated with Irreversible Electroporation for Locally Advanced Pancreatic Cancer

Introduction. In patients with locally advanced pancreatic cancer (LAPC), IRE has been shown to be safe for local disease control and palliation. As IRE continues to gain acceptance it is important to characterize the expected imaging findings. Materials and Methods. A review of our prospective soft tissue ablation registry from July 2010 to June 2013 was performed on patients who had undergone IRE for LAPC. Five masses treated with intraoperative IRE ablation for pancreatic tumors that underwent CT imaging before and after ablation were reviewed. Results and Discussion. Following IRE, the postablation bed is larger than the original ablated tumor. This ablation zone may get smaller in size (due to decreased edema and hyperemia) in the following months and more importantly remains stable provided there is no recurrence. In cases of recurrent disease there is increased size of the ablation bed, mass effect, and new or worsening vascular encasement or occlusion. Conclusion. CT imaging remains the best current imaging modality to assess post-IRE ablation changes. Serial imaging over at least 2-6 months must be employed to detect recurrence by comparing with prior studies in conjunction with clinical and serum studies. Larger imaging studies are underway to evaluate a more ideal imaging modality for this unique patient population.

Microwave ablation of pancreatic head cancer: safety and efficacy

PURPOSE

To evaluate the safety and efficacy of percutaneous microwave (MW) ablation treatment in locally advanced, nonresectable, nonmetastatic pancreatic head cancer.

MATERIALS AND METHODS

Ten patients with pancreatic head cancer treated with percutaneous (n = 5) or laparotomic (n = 5) MW ablation were retrospectively reviewed. The MW generator used (45 W at 915 MHz) was connected by coaxial cable to 14-gauge straight MW antennas with a 3.7- or 2-cm radiating section. One or two antennae were used, with an ablation time of 10 minutes. Ultrasonographic (US) and combined US/cone-beam computed tomographic (CT) guidance were used in five patients each. Follow-up was performed by CT after 1, 3, 6, and, when possible, 12 months. Tumor response was assessed per Response Evaluation Criteria In Solid Tumors (version 1.1) and Choi criteria. The feasibility, safety, and major and minor complications associated with quality of life (QOL) were recorded prospectively.

RESULTS

The procedure was feasible in all patients (100%). One late major complication was observed in one patient, and no visceral injury was detected. No patient had further surgery, and all minor complications resolved during the hospital stay. An improvement in QOL was observed in all patients despite a tendency to return to preoperative levels in the months following the procedure, without the influence of minor complications. No repeat treatment was performed.

CONCLUSIONS

Despite the small number of patients, the present results can be considered encouraging, showing that MW ablation is a feasible approach in the palliative treatment of pancreatic tumors.

Minimally invasive ablation treatment for locally advanced pancreatic adenocarcinoma

Pancreatic adenocarcinoma is an aggressive tumour with an extremely poor prognosis, which has not changed significantly during the last 30 years. Prolonged survival is achieved only by R0 resection with macroscopic tumour clearance. However, the majority of the cases are considered inoperable at diagnosis due to local spread or presence of metastatic disease. Chemoradiotherapy is not tolerated by all patients and still fails to prolong survival significantly; neoadjuvant treatment also has limited results on pain control or tumour downstaging. In recent years, there has been a growing interest in the use of ablation therapy for the treatment of nonresectable tumours in various organs. Ablation techniques are based on direct application of chemical, thermal, or electrical energy to a tumour, which leads to cellular necrosis. With ablation, tumour cytoreduction, local control, and relief from symptoms are obtained in the majority of the patients. Inoperable cases of pancreatic adenocarcinoma have been treated by various ablation techniques in the last few years with promising results. The purpose of this review is to present the current status of local ablative therapies in the treatment of pancreatic adenocarcinoma and to investigate on the efficiency and the future trends.