Dual mode single agent thermochemical ablation by simultaneous release of heat energy and acid: hydrolysis of electrophiles

Veterinary Clinics: Tumor Ablation

Over the past decade, interventional oncology techniques have become integrated into the treatment plans of companion animals with cancer on a regular basis. Although procedures such as stenting are performed commonly, other less frequently utilized techniques for locoregional therapy, such as embolization and ablation, are emerging and demonstrating promise. Tumor ablation techniques are categorized into two subgroups: chemical ablation and energy-based ablation. Increased utilization of ablation will allow for the determination of specific indications and evaluation of outcomes for these techniques.

Image-guided chemistry altering biology: An in vivo study of thermoembolization

RATIONALE

Advances in image-guided drug delivery for liver cancer have shown a significant survival benefit. However, incomplete treatment is common and residual disease is often found in explanted liver specimens. In addition, the need to treat a malignancy from multiple mechanisms at the same time for optimal outcomes is becoming more widely appreciated. To address this, we hypothesized that an exothermic chemical reaction could be performed in situ. Such a strategy could in principle combine several angles of attack, including ischemia, hyperthermia, acidic protein denaturation, and metabolic modulation of the local environment.

METHODS

The University of Texas MD Anderson Cancer Center Institutional Animal Care and Use Committee approved this study. Outbred swine (25-35 kg, 5 control and 5 experimental) were treated under general anesthesia. Embolization was performed with coaxial microcatheter technique in a segmental hepatic arterial branch using either ethiodized oil as control or with thermoembolic solutionBlood samples were obtained before, immediately after, and the day following the procedure just before CT scans and euthanasia. Livers were explanted and samples were obtained for histologic analysis.

RESULTS

All animals survived the procedure and laboratory values of the control and experimental groups remained within normal limits. The control group had a diffuse or cloudy pattern of attenuation on follow-up CT scan the day after, consistent with gradual antegrade sinusoidal transit of the embolic material. The experimental group had clearly defined vascular casts with some degree of peripheral involvement. At histology, the control group samples had the appearance of normal liver, whereas the experimental group had coagulative necrosis in small pale, punctate areas extending several hundred microns away from the treated vessels and a brisk inflammatory response just outside the margins.

CONCLUSION

In situ chemistry via thermoembolization shows early promise as a fundamentally new tactic for image-guided therapy of solid tumors.

First In Vivo Test of Thermoembolization: Turning Tissue Against Itself Using Transcatheter Chemistry in a Porcine Model

PURPOSE

Embolotherapies are commonly used for management of primary liver cancer. Explant studies of treated livers, however, reveal an untreated tumor in a high fraction of cases. To improve on this, we propose a new concept referred to as thermoembolization. In this technique, the embolic material reacts in local tissues. Highly localized heat energy is released simultaneously with the generation of acid in the target vascular bed. Combined with ischemia, this should provide a multiplexed attack. We report herein our initial results testing the feasibility of this method in vivo.

MATERIALS AND METHODS

Institutional approval was obtained, and three outbred swine were treated in a segmental hepatic artery branch (right or left medial lobe) with thermoembolic material (100, 400, or 500 µL). Solutions (2 or 4 mol/L) of an acid chloride were made using ethiodized oil as the vehicle. Animals were housed overnight, scanned by CT, and euthanized. Necropsy samples of treated tissue were obtained for histologic analysis.

RESULTS

All animals survived the procedure. Vascular stasis occurred rapidly in all cases despite the small volumes used. The lower concentration (2 mol/L) penetrated more distally than the 4 mol/L solution. At CT the following day, vascular casts of ethiodized oil were observed, indicating recanalization had not occurred. Histology specimens demonstrated coagulative necrosis centered on the vessel lumen extending for several hundred microns with a peripheral inflammatory infiltrate.

CONCLUSIONS

Thermoembolization is a new technique for embolization with initial promise. However, results indicate much work must be done to optimize the technique.

Thermochemical ablation therapy of VX2 tumor using a permeable oil-packed liquid alkali metal

Objective

Alkali metal appears to be a promising tool in thermochemical ablation, but, it requires additional data on safety is required. The objective of this study was to explore the effectiveness of permeable oil-packed liquid alkali metal in the thermochemical ablation of tumors.

Methods

Permeable oil-packed sodium–potassium (NaK) was prepared using ultrasonic mixing of different ratios of metal to oil. The thermal effect of the mixture during ablation of muscle tissue ex vivo was evaluated using the Fluke Ti400 Thermal Imager. The thermochemical effect of the NaK-oil mixture on VX2 tumors was evaluated by performing perfusion CT scans both before and after treatment in 10 VX2 rabbit model tumors. VX2 tumors were harvested from two rabbits immediately after treatment to assess their viability using trypan blue and hematoxylin and eosin (H.E.) staining.

Results

The injection of the NaK–oil mixture resulted in significantly higher heat in the ablation areas. The permeable oil controlled the rate of heat released during the NaK reaction with water in the living tissue. Perfusion computed tomography and its parameter map confirmed that the NaK–oil mixture had curative effects on VX2 tumors. Both trypan blue and H.E. staining showed partial necrosis of the VX2 tumors.

Conclusions

The NaK–oil mixture may be used successfully to ablate tumor tissue in vivo. With reference to the controlled thermal and chemical lethal injury to tumors, using a liquid alkali in ablation is potentially an effective and safe method to treat malignant tumors.

Image-guided tumor ablation: standardization of terminology and reporting criteria--a 10-year update

Image-guided tumor ablation has become a well-established hallmark of local cancer therapy. The breadth of options available in this growing field increases the need for standardization of terminology and reporting criteria to facilitate effective communication of ideas and appropriate comparison among treatments that use different technologies, such as chemical (eg, ethanol or acetic acid) ablation, thermal therapies (eg, radiofrequency, laser, microwave, focused ultrasound, and cryoablation) and newer ablative modalities such as irreversible electroporation. This updated consensus document provides a framework that will facilitate the clearest communication among investigators regarding ablative technologies. An appropriate vehicle is proposed for reporting the various aspects of image-guided ablation therapy including classification of therapies, procedure terms, descriptors of imaging guidance, and terminology for imaging and pathologic findings. Methods are addressed for standardizing reporting of technique, follow-up, complications, and clinical results. As noted in the original document from 2003, adherence to the recommendations will improve the precision of communications in this field, leading to more accurate comparison of technologies and results, and ultimately to improved patient outcomes.

Image-guided tumor ablation: standardization of terminology and reporting criteria--a 10-year update

Image-guided tumor ablation has become a well-established hallmark of local cancer therapy. The breadth of options available in this growing field increases the need for standardization of terminology and reporting criteria to facilitate effective communication of ideas and appropriate comparison among treatments that use different technologies, such as chemical (eg, ethanol or acetic acid) ablation, thermal therapies (eg, radiofrequency, laser, microwave, focused ultrasound, and cryoablation) and newer ablative modalities such as irreversible electroporation. This updated consensus document provides a framework that will facilitate the clearest communication among investigators regarding ablative technologies. An appropriate vehicle is proposed for reporting the various aspects of image-guided ablation therapy including classification of therapies, procedure terms, descriptors of imaging guidance, and terminology for imaging and pathologic findings. Methods are addressed for standardizing reporting of technique, follow-up, complications, and clinical results. As noted in the original document from 2003, adherence to the recommendations will improve the precision of communications in this field, leading to more accurate comparison of technologies and results, and ultimately to improved patient outcomes. Online supplemental material is available for this article .

Development of a Simple Miniature Thermochemical Ablation Device Suitable for Tumor Ablation Research in Rodent Models

Thermochemical ablation is a recently developed minimally invasive method with potential for solid tumor treatment such as in liver cancer. A recently described prototype device, however, is too large for use in the more common rodent models of cancer. In this report we describe a simple, low-cost variant of the device that is easy to assemble, small enough to be readily applicable to small animal models, and then demonstrate its use in an ex vivo model for ablation. It should therefore enable study of the method without requiring specialized equipment or access to a machine shop for device manufacture.