New Developments in Image-Guided Percutaneous Irreversible Electroporation of Solid Tumors

Irreversible electroporation combined with anti-programmed cell death protein 1 therapy promotes tumor antigen-specific CD8+ T cell response

BACKGROUND

Irreversible electroporation (IRE) is a novel local tumor ablation approach with the potential to activate the host's immune system. However, this approach is insufficient to prevent cancer progression, and complementary approaches are required for effective immunotherapy.

AIM

To assess the immunomodulatory effects and mechanism of IRE combined anti-programmed cell death protein 1 (PD-1) treatment in subcutaneous pancreatic cancer models.

METHODS

C57BL-6 tumor-bearing mice were randomly divided into four groups: Control group; IRE group; anti-PD-1 group; and IRE + anti-PD-1 group. Tumor-infiltrating T, B, and natural killer cell levels and plasma concentrations of T helper type 1 cytokines (interleukin-2, interferon-γ, and tumor necrosis factor-α) were evaluated. Real-time PCR was used to determine the expression of CD8 (marker of CD8+ T cells) in tumor tissues of the mice of all groups at different points of time. The growth curves of tumors were drawn.

RESULTS

The results demonstrated that the IRE + anti-PD-1 group exhibited significantly higher percentages of T lymphocyte infiltration, including CD4+ and CD8+ T cells compared with the control group. Additionally, the IRE + anti-PD-1 group showed increased infiltration of natural killer and B cells, elevated cytokine levels, and higher CD8 mRNA expression. Tumor volume was significantly reduced in the IRE + anti-PD-1 group, indicating a more pronounced therapeutic effect.

CONCLUSION

The combination of IRE and anti-PD-1 therapy promotes CD8+ T cell immunity responses, leading to a more effective reduction in tumor volume and improved therapeutic outcomes, which provides a new direction for ablation and immunotherapy of pancreatic cancer.

Pulsed field ablation in medicine: irreversible electroporation and electropermeabilization theory and applications

BACKGROUND

Focal ablation techniques are integral in the surgical intervention of diseased tissue, where it is necessary to minimize damage to the surrounding parenchyma and critical structures. Irreversible electroporation (IRE) and high-frequency IRE (H-FIRE), colloquially called pulsed-field ablation (PFA), utilize high-amplitude, low-energy pulsed electric fields (PEFs) to nonthermally ablate soft tissue. PEFs induce cell death through permeabilization of the cellular membrane, leading to loss of homeostasis. The unique nonthermal nature of PFA allows for selective cell death while minimally affecting surrounding proteinaceous structures, permitting treatment near sensitive anatomy where thermal ablation or surgical resection is contraindicated. Further, PFA is being used to treat tissue when tumor margins are not expected after surgical resection, termed margin accentuation. This review explores both the theoretical foundations of PFA, detailing how PEFs induce cell membrane destabilization and selective tissue ablation, the outcomes following treatment, and its clinical implications across oncology and cardiology.

CONCLUSIONS

Clinical experience is still progressing, but reports have demonstrated that PFA reduces complications often seen with thermal ablation techniques. Mounting oncology data also support that PFA produces a robust immune response that may prevent local recurrences and attenuate metastatic disease. Despite promising outcomes, challenges such as optimizing field delivery and addressing variations in tissue response require further investigation. Future directions include refining PFA protocols and expanding its application to other therapeutic areas like benign tissue hyperplasia and chronic bronchitis.

Effect of Transforming Growth Factor-β Inhibition on Ureteral and Renal Scarring in a Rat Model of Upper Urinary Tract Ablation with Irreversible Electroporation

Objective

To determine whether adjuvant transforming growth factor-β (TGF-β) inhibition with pirfenidone (PFD) can mitigate ureteral wall scarring and related complications in a rat model of upper urinary tract ablation with irreversible electroporation (IRE).

Methods

Transmural ablation of the ureter was performed with IRE in 24 rats. Post-IRE, animals were randomly assigned to receive PFD or no drug, followed by euthanasia at 2-, 5-, or 10-days. The complete urinary tract was extracted, and the dimensions of kidney and ureter were measured. Immunohistochemistry was performed to quantify collagen deposition, α-smooth muscle actin (α-SMA) (myofibroblasts in ureter and kidney) and TGF-β (ureter only).

Results

Enlargement of the kidney and ureteral dilatation were apparent during gross necropsy of rats from both cohorts. The changes in anatomical measurements were significantly reduced in rats receiving PFD at Day 5 and 10 (p = 0.02 and 0.04, respectively). Collagen levels in the ureters gradually increased in rats from both cohorts at Day 2 and 5, but started to reduce by Day 10 in rats receiving PFD when compared with no treatment (p = 0.04). Myofibroblast levels and TGF-β staining in the ureters was lower in rats receiving PFD on Day 5 and 10, respectively (p < 0.01). Collagen levels and myofibroblast staining of the kidneys from rats receiving PFD was significantly lower than control on Days 5 and 10.

Conclusion

Adjuvant PFD can reduce myofibroblast activity and ureteral fibrosis at the site of IRE ablation, enabling safe soft tissue ablation adjacent or involving the upper urinary tract.

Oncologic Outcomes after Percutaneous Ablation for Colorectal Liver Metastases: An Updated Comprehensive Review

Colorectal cancer is a major cause of cancer-related mortality, with liver metastases occurring in over a third of patients, and is correlated with poor prognosis. Despite surgical resection being the primary treatment option, only about 20% of patients qualify for surgery. Current guidelines recommend thermal ablation either alone or combined with surgery to treat limited hepatic metastases, provided that all visible disease can be effectively eradicated. Several ablation modalities, including radiofrequency ablation, microwave ablation, cryoablation, irreversible electroporation and histotripsy, are part of the percutaneous ablation armamentarium. Thermal ablation, including radiofrequency, microwave ablation and cryoablation, can offer local tumor control rates comparable to limited resection for selected tumors that can be ablated with margins. This review aims to encapsulate the current clinical evidence regarding the efficacy and oncologic outcomes after percutaneous ablation for the treatment of colorectal liver metastatic disease.

Ultrasound-guided percutaneous high-frequency irreversible electroporation in porcine livers using four electrode needles: A feasibility and safety study

BACKGROUND

Malignant liver tumors seriously endanger human health. Among different therapeutic approaches, high-frequency irreversible electroporation (H-FIRE) is a recently emerging tumor ablation technique. The objective of this study was to evaluate the feasibility and safety of ultrasound-guided percutaneous H-FIRE using four electrode needles in porcine livers.

METHODS

Twelve experimental pigs underwent percutaneous H-FIRE ablation using a compound steep-pulse therapeutic device. Liver tissues adjacent to the gallbladder, blood vessels, and bile ducts were selected as the ablation targets. Pigs were randomly divided into three groups: (1) immediately after ablation (N = 4), (2) 2 days after ablation (N = 4), and (3) 7 days after ablation (N = 4). Blood routine, liver and kidney function, and myocardial enzyme levels were measured before and after ablation. Ultrasound, contrast-enhanced ultrasound (CEUS), contrast-enhanced magnetic resonance imaging (MRI), and hematoxylin-eosin staining were performed to evaluate the ablation performance.

RESULTS

Ultrasound-guided percutaneous H-FIRE ablations using four electrode needles were successfully performed in all 12 experimental pigs. The general conditions of the pigs, including postoperative activities and feeding behaviors, were normal, with no significant changes compared with the preoperative conditions. The imaging features of ultrasound, CEUS, and MRI demonstrated no significant changes in the gallbladder walls, bile ducts, or blood vessels close to the ablation areas. Laboratory tests showed that liver function indices and myocardial enzymes increased temporarily after H-FIRE ablation, but decreased to normal levels at 7 days after ablation. Histopathological examinations of porcine liver specimens showed that this technique could effectively ablate the target areas without damaging the surrounding or internal vascular systems and gallbladder.

CONCLUSIONS

This study demonstrated the feasibility and safety of ultrasound-guided percutaneous H-FIRE ablation in porcine livers in vivo, and proposed a four-needle method to optimize its clinical application.

Interventional Radiology Locoregional Therapies for Intrahepatic Cholangiocarcinoma

Surgical resection remains the cornerstone of curative treatment for intrahepatic cholangiocarcinoma (iCCA), but this option is only available to a small percentage of patients. For patients with unresectable iCCA, systemic therapy with gemcitabine and platinum-based agents represents the mainstay of treatment; however, the armamentarium has grown to include targeted molecular therapies (e.g., FGFR2 inhibitors), use of adjuvant therapy, liver transplantation in select cases, immunotherapy, and locoregional liver-directed therapies. Despite advances, iCCA remains a challenge due to the advanced stage of many patients at diagnosis. Furthermore, given the improving options for systemic therapy and the fact that the majority of iCCA patients succumb to disease progression in the liver, the role of locoregional therapies has increased. This review will focus on the expanding role of interventional radiology and liver-directed therapies in the treatment of iCCA.

Non-Thermal Liver Ablation: Existing and New Technology

Cancer has and continues to be a complex health crisis plaguing millions around the world. Alcohol ablation was one of the initial methods used for the treatment of liver lesions. It was surpassed by thermal ablation which has played a big role in the therapeutic arsenal for primary and metastatic liver tumors. However, thermal ablation has several shortcomings and limitations that prompted the development of alternative technologies including electroporation and histotripsy. Percutaneous alcohol injection in the liver lesion leads to dehydration and coagulative necrosis. This technology is limited to the lesion with relative sparing of the surrounding tissue, making it safe to use adjacent to sensitive structures. Electroporation utilizes short high-voltage pulses to permeabilize the cell membrane and can result in cell death dependent on the threshold reached. It can effectively target the tumor margins and has lower damage rates to surrounding structures due to the short pulse duration. Histotripsy is a novel technology, and although the first human trial was just completed, its results are encouraging, given the sharp demarcation of the targeted tissue, lack of thermal damage, and potential for immunomodulation of the tumor microenvironment. Herein, we discuss these techniques, their uses, and overall clinical benefit.