Thermal ablation

Strategies to Improve Drug Delivery Across the Blood-Brain Barrier for Glioblastoma

PURPOSE OF REVIEW

Glioblastoma remains resistant to most conventional treatments. Despite scientific advances in the past three decades, there has been a dearth of effective new treatments. New approaches to drug delivery and clinical trial design are needed.

RECENT FINDINGS

We discuss how the blood-brain barrier and tumor microenvironment pose challenges for development of effective therapies for glioblastoma. Next, we discuss treatments in development that aim to overcome these barriers, including novel drug designs such as nanoparticles and antibody-drug conjugates, novel methods of drug delivery, including convection-enhanced and intra-arterial delivery, and novel methods to enhance drug penetration, such as blood-brain barrier disruption by focused ultrasound and laser interstitial thermal therapy. Lastly, we address future opportunities, positing combination therapy as the best strategy for effective treatment, neoadjuvant and window-of-opportunity approaches to simultaneously enhance therapeutic effectiveness with interrogation of on-treatment biologic endpoints, and adaptive platform and basket trials as imperative for future trial design. New approaches to GBM treatment should account for the blood-brain barrier and immunosuppression by improving drug delivery, combining treatments, and integrating novel clinical trial designs.

Development and preclinical evaluation of multifunctional hydrogel for precise thermal protection during thermal ablation

Image-guided thermal ablation (TA), which is less invasive, has been widely applied for treating various kinds of tumors. However, TA still poses the potential risk of thermal damage to sensitive tissue nearby. Therefore, an adjunctive thermoprotective hydrodissection technique with constant injection of 5% glucose (5% Glu) has currently been adopted for clinical application, but this may be hazardous to humans. In this study, a multifunctional hyaluronic acid-based hydrogel (HA-Dc) was developed for hydrodissection. Compared with 5% Glu (the most clinically used solution) and the previously reported F127 hydrogel, the HA-Dc hydrogel was studied in vitro in a porcine liver model and in vivo in a rabbit model and showed good injectability and better tissue retention, stability, and thermoprotective properties throughout the TA procedure. Furthermore, in the preclinical evaluation in a Macaca fascicularis (M. fascicularis) model, HA-Dc showed excellent performance in terms of stricter neuroprotection compared with 5% Glu. In addition, the HA-Dc hydrogel with good biocompatibility and controllable degradation behavior in vivo could be a promising platform for thermal protection during clinical TA procedures.

Tumor phantom model for MRI-guided focused ultrasound ablation studies

BACKGROUND

The persistent development of focused ultrasound (FUS) thermal therapy in the context of oncology creates the need for tissue-mimicking tumor phantom models for early-stage experimentation and evaluation of relevant systems and protocols.

PURPOSE

This study presents the development and evaluation of a tumor-bearing tissue phantom model for testing magnetic resonance imaging (MRI)-guided FUS (MRgFUS) ablation protocols and equipment based on MR thermometry.

METHODS

Normal tissue was mimicked by a pure agar gel, while the tumor simulator was differentiated from the surrounding material by including silicon dioxide. The phantom was characterized in terms of acoustic, thermal, and MRI properties. US, MRI, and computed tomography (CT) images of the phantom were acquired to assess the contrast between the two compartments. The phantom's response to thermal heating was investigated by performing high power sonications with a 2.4 MHz single element spherically focused ultrasonic transducer in a 3T MRI scanner.

RESULTS

The estimated phantom properties fall within the range of literature-reported values of soft tissues. The inclusion of silicon dioxide in the tumor material offered excellent tumor visualization in US, MRI, and CT. MR thermometry revealed temperature elevations in the phantom to ablation levels and clear evidence of larger heat accumulation within the tumor owing to the inclusion of silicon dioxide.

CONCLUSION

Overall, the study findings suggest that the proposed tumor phantom model constitutes a simple and inexpensive tool for preclinical MRgFUS ablation studies, and potentially other image-guided thermal ablation applications upon minimal modifications.

Vaccines in Breast Cancer: Challenges and Breakthroughs

Breast cancer is a problem for women's health globally. Early detection techniques come in a variety of forms ranging from local to systemic and from non-invasive to invasive. The treatment of cancer has always been challenging despite the availability of a wide range of therapeutics. This is either due to the variable behaviour and heterogeneity of the proliferating cells and/or the individual's response towards the treatment applied. However, advancements in cancer biology and scientific technology have changed the course of the cancer treatment approach. This current review briefly encompasses the diagnostics, the latest and most recent breakthrough strategies and challenges, and the limitations in fighting breast cancer, emphasising the development of breast cancer vaccines. It also includes the filed/granted patents referring to the same aspects.

Development of an US, MRI, and CT imaging compatible realistic mouse phantom for thermal ablation and focused ultrasound evaluation

Tissue mimicking phantoms (TMPs) play an essential role in modern biomedical research as cost-effective quality assurance and training tools, simultaneously contributing to the reduction of animal use. Herein, we present the development and evaluation of an anatomically accurate mouse phantom intended for image-guided thermal ablation and Focused Ultrasound (FUS) applications. The proposed mouse model consists of skeletal and soft tissue mimics, whose design was based on the Computed tomography (CT) scans data of a live mouse. Advantageously, it is compatible with US, CT, and Magnetic Resonance Imaging (MRI). The compatibility assessment was focused on the radiological behavior of the phantom due to the lack of relevant literature. The X-ray linear attenuation coefficient of candidate materials was estimated to assess the one that matches best the radiological behavior of living tissues. The bone part was manufactured by Fused Deposition Modeling (FDM) printing using Acrylonitrile styrene acrylate (ASA) material. For the soft-tissue mimic, a special mold was 3D printed having a cavity with the unique shape of the mouse body and filled with an agar-based silica-doped gel. The mouse phantom accurately matched the size and reproduced the body surface of the imaged mouse. Tissue-equivalency in terms of X-ray attenuation was demonstrated for the agar-based soft-tissue mimic. The phantom demonstrated excellent MRI visibility of the skeletal and soft-tissue mimics. Good radiological contrast between the skeletal and soft-tissue models was also observed in the CT scans. The model was also able to reproduce realistic behavior during trans-skull sonication as proved by thermocouple measurements. Overall, the proposed phantom is inexpensive, ergonomic, and realistic. It could constitute a powerful tool for image-guided thermal ablation and FUS studies in terms of testing and optimizing the performance of relevant equipment and protocols. It also possess great potential for use in transcranial FUS applications, including the emerging topic of FUS-mediated blood brain barrier (BBB) disruption.

Image-Guided Precision Treatments

Chemotherapy, radiotherapy, and surgery are traditional cancer treatments, which usually produce unpredictable side effects and potential risks to normal healthy organs/tissues. Thus, safe and reliable treatment strategies are urgently required for maximized therapeutic efficiency to lesions and minimized risks to healthy regions. To this end, molecular imaging is responsible to undertake a specific targeting therapy. Besides that, the image guidance as a precision visualized approach for real-time in situ evaluations as well as an intraoperational navigation approach has earned attractive attention in the past decade. Along with the rapid development of multifunctional micro-/nanobiomaterials, versatile cutting-edge and advanced therapy strategies (e.g., thermal therapy, dynamic therapy, gas therapy, etc.) have been achieved and greatly contributed to the image-guided precision treatments in every aspect. Therefore, this chapter aims to discuss about both traditional and advanced cancer treatments and especially to elucidate the important roles that visualized medicine has been playing in the image-guided precision treatments.

Percutaneous Management of Breast Cancer: a Systematic Review

PURPOSE OF REVIEW

Surgical treatment of breast cancer is becoming increasingly more minimally invasive. We review the development status of percutaneous management for primary breast cancer and the evidence relating to tumor size as a fundamental determinant of treatment clinical outcome.

RECENT FINDINGS

It is safe and feasible for percutaneous management to treat breast cancer. For tumor size ≤ 2 cm, percutaneous management is a promising alternative modality. For tumor size ≤ 3 cm, it is controversial whether percutaneous management can achieve similar effects to surgery, especially its long-term effects. For tumor size > 3 cm, it is still in the initial exploration stage and showed the potential in the treatment of unresectable cancer by benefitting the local control of primary cancer. Percutaneous management of breast cancer is a valuable method for breast cancer treatment in selected patients. However, it will be necessary to provide the high level of evidence for widespread clinical application.

Dual-modality fibre optic probe for simultaneous ablation and ultrasound imaging

All-optical ultrasound (OpUS) is an emerging high resolution imaging paradigm utilising optical fibres. This allows both therapeutic and imaging modalities to be integrated into devices with dimensions small enough for minimally invasive surgical applications. Here we report a dual-modality fibre optic probe that synchronously performs laser ablation and real-time all-optical ultrasound imaging for ablation monitoring. The device comprises three optical fibres: one each for transmission and reception of ultrasound, and one for the delivery of laser light for ablation. The total device diameter is < 1 mm. Ablation monitoring was carried out on porcine liver and heart tissue ex vivo with ablation depth tracked using all-optical M-mode ultrasound imaging and lesion boundary identification using a segmentation algorithm. Ablation depths up to 2.1 mm were visualised with a good correspondence between the ultrasound depth measurements and visual inspection of the lesions using stereomicroscopy. This work demonstrates the potential for OpUS probes to guide minimally invasive ablation procedures in real time.

Ultrasound Deep Brain Stimulation Modulates Body Temperature in Mice

Body temperature plays a critical role in rehabilitation, and numerous studies proved that the regulation of body temperature contributes to the sensorimotor recovery of patients with brain diseases such as stroke. The hypothalamus plays a key role in thermoregulation. Ultrasound deep brain stimulation (UDBS) can noninvasively modulate deep brain nuclei and have potential applications in the treatment of Parkinson's disease, Alzheimer's disease, and depression, among others. The purpose of this study was to investigate whether ultrasound stimulation of the hypothalamus could regulate body temperature in free-moving mice. Results showed that thermoregulation was related to ultrasonic parameters (pulse repetition frequency (PRF), duty cycle, total time, and acoustic pressure). UDBS of the preoptic area of the anterior hypothalamus at 500 Hz PRF could significantly reduce body temperature ( [Formula: see text] at t = 5 min, [Formula: see text] at t = 10 min, [Formula: see text] at t = 15 min). Meanwhile, UDBS of the dorsomedial hypothalamus at 10 Hz PRF triggered a significant increase in body temperature ( [Formula: see text] at t = 5 min, [Formula: see text] at t = 10 min). These results suggest that UDBS, as a noninvasive neuromodulation tool, may play a key role in the future clinical treatment of malignant hyperthermia and hypothermia.

Analysis of Coil Configurations for a Contactless Thermal Tumor Ablation With Implanted Devices

In the wide field of tumor treatment, thermal ablation procedures are very promising. Alternating magnetic fields are used to transfer the energy from outside the patient to the tumor area located anywhere in the body. This energy is converted to heat by implanted devices located in the tumor area. In this paper, the spatial distribution of the magnetic field of different circular coil configurations is analyzed and optimized with focus on patients' safety and on coil configuration performance. The analysis is based on several performance criteria and is conducted with respect to the worst case scenario of a contactless thermal tumor ablation of deep-seated tumors, in which the energy has to be transferred over a considerably large distance. The magnetic field and the specific absorption rate (SAR) are calculated numerically and the performance criteria are evaluated based on a model of a human body including a tumor area. The most suitable coil configurations for different application scenarios are presented and a thermal analysis is done. Based on this, the minimum required heating power, coil current and number of coil windings, and the corresponding maximum SAR to achieve an adequate rise of tissue temperature are evaluated. For a heating power of 1.45 W, a minimum SAR of 130 mW/kg, a maximum power transfer efficiency of 1.05%, and a maximum coupling coefficient of 0.00695 is achieved. This paper shows the potential to enhance the safety of the patients significantly by choosing the appropriate coil configuration for a specific application scenario.

The Roles of Magnetic Resonance-Guided Focused Ultrasound in Pain Relief in Patients With Bone Metastases: A Systemic Review and Meta-Analysis

Objective

Cancer pain, the most common skeleton-related event of bone metastases, significantly disturbs patients' life. MRI-guided focused ultrasound (MRgFUS) is a therapeutic option to relieve pain; however, its efficacy and safety have not been fully explored. Therefore, we aim to conduct a meta-analysis on studies reporting MRgFUS for patients with bone metastases.

Methods

Randomized controlled trials (RCT) and non-RCTs on MRgFUS treatment for patients with bone metastases were collected using PubMed, MEDLINE In-Process (US National Library of Medicine), National Institutes of Health (US National Library of Medicine), Embase (Elsevier), Web of Science, CINAHL, and the Cochrane Library between August 2007 and September 2019. Data on quantitative pain assessment before/after MRgFUS, response rate, and complication were extracted and analyzed.

Results

Fifteen eligible studies with 362 patients were selected in this meta-analysis. The average pain score was 6.74 (95% CI: 6.30-7.18) at baseline, 4.15 (95% CI: 3.31-4.99) at 0-1 week, 3.09 (95% CI: 2.46-3.72) at 1-5 weeks, and 2.28 (95% CI: 1.37-3.19) at 5-14 weeks. Compared with baseline, the pain improvement at 0-1 week was 2.54 (95% CI: 1.92-3.16, p < 0.01), at 1-5 weeks was 3.56 (95% CI: 3.11-4.02, p < 0.01), and at 5-14 weeks was 4.22 (95% CI: 3.68-4.76, p < 0.01). Change from baseline in OMEDD at 2 weeks after treatment was -15.11 (95% CI: -34.73, 4.50), at 1 month after treatment was -10.87 (95% CI: -26.32, 4.58), and at 3 months after treatment was -5.53 (95% CI: -20.44, 9.38). The overall CR rate was 0.36 (95% CI: 0.24-0.48), PR rate was 0.47 (95% CI: 0.36-0.58), and NR rate was 0.23 (95% CI: 0.13-0.34). Among 14 studies including 352 patients, 93 (26.4%) patients with minor complications and 5 (1.42%) patients with major complications were recorded.

Conclusion

This meta-analysis identifies MRgFUS as a reliable therapeutic option to relieve cancer pain for patients with metastatic bone tumors with controllable related complications.

An Acceptor-π-Donor Structured Organic Chromophore for NIR Triggered Thermal Ablation of Tumor via DNA Damage-Mediated Apoptosis

INTRODUCTION

It will be challenging to develop high-performance organic chromophores for light-triggered thermal ablation of the tumor. Besides, the mechanisms of organic chromophores for tumor therapy remain unclear. Herein, an acceptor-π-donor (A-π-D) structured organic chromophore based on 2-dicyanomethylenethiazole named PTM was developed for photothermal therapy (PTT) of tumors.

METHODS AND RESULTS

Biocompatible PTM nanoparticles (PTM NPs) were fabricated by enclosing PTM with Pluronic F-127. The results of optical and photothermal properties of PTM NPs showed robust near-infrared (NIR) absorption, excellent photostability and high photothermal conversion efficiency (56.9%). The results of flow cytometry, fluorescence microscopy, apoptosis, CCK-8 assays and animal experiments showed that PTM NPs had a good killing effect on tumors under NIR laser irradiation. Furthermore, mechanistic studies, RNA-seq and biological analysis revealed that PTM NPs can cause tumor cell death via DNA damage-mediated apoptosis.

CONCLUSION

Light-induced thermal ablation effects of PTM NPs in vitro and vivo were surveyed. Collectively, our studies provided a new approach to developing a safe and effective photothermal agent for cancer treatment.

A preliminary study on ultrasound-guided percutaneous microwave ablation for palliative treatment of advanced head and neck malignancies

OBJECTIVE

To evaluate the safety and efficacy of ultrasound (US)-guided percutaneous microwave ablation (UgPMWA) for palliative treatment of advanced head and neck malignancies.

MATERIALS AND METHODS

This study includes 18 consecutive patients with advanced head and neck malignancies (n = 24), who have undergone UgPMWA for palliative treatment at our institution from December 2016 to April 2020. The maximum diameter and volume of the tumor were assessed by US, CT or MRI before microwave ablation (MWA), 1, 3 and 6 months after MWA and every 6 months thereafter. The quality of life was clinically assessed by the University of Washington Head and Neck Quality of Life questionnaire (UW-QOl).

RESULTS

The success rate of tumor-targeting microwave antenna placement was 100%. No nerve injury and serious complications or death occurred during the perioperative period. The follow-up duration varied from 1 month to 38 months (11.56 ± 10.23 months) among patients. By the last follow-up before submission, the value of maximum diameter (5.00 ± 2.90 vs 3.28 ± 2.11 cm. p < 0.05) and tumor volume decreased significantly（74.35 ± 46.88 vs 47.45 ± 24.08 cm³. p < 0.05）respectively after palliative treatment with UgPMWA. UW-QOl of the patients was improved (59.24 ± 11.51 vs 69.84 ± 8.12, p < 0.05).

CONCLUSION

UgPMWA is safe and effective for the palliative treatment of head and neck malignancies. Ultrasonic guidance can indicate an accurate location of the microwave antenna. It can also monitor the ablation area in real-time during the operation to avoid damage to surrounding normal tissues.

Image-guided Microinvasive Percutaneous Treatment of Breast Lesions: Where Do We Stand?

Treatment of breast lesions has evolved toward the use of less-invasive or minimally invasive techniques. Minimally invasive treatments destroy focal groups of cells without surgery; hence, less anesthesia is required, better cosmetic outcomes are achieved because of minimal (if any) scarring, and recovery times are shorter. These techniques include cryoablation, radiofrequency ablation, microwave ablation, high-intensity focused US, laser therapy, vacuum-assisted excision, and irreversible electroporation. Each modality involves the use of different mechanisms and requires specific considerations for application. To date, only cryoablation and vacuum-assisted excision have received U.S. Food and Drug Administration approval for treatment of fibroadenomas and have been implemented as part of the treatment algorithm by the American Society of Breast Surgeons. Several clinical studies on this topic have been performed on outcomes in patients with breast cancer who were treated with these techniques. The results are promising, with more data for radiofrequency ablation and cryoablation available than for other minimally invasive methods for treatment of early-stage breast cancer. Clinical decisions should be made on a case-by-case basis, according to the availability of the technique. MRI is the most effective imaging modality for postprocedural follow-up, with the pattern of enhancement differentiating residual or recurrent disease from postprocedural changes. ^©RSNA, 2021.

Functionalization of Metal and Carbon Nanoparticles with Potential in Cancer Theranostics

Cancer theranostics is a new concept of medical approach that attempts to combine in a unique nanoplatform diagnosis, monitoring and therapy so as to provide eradication of a solid tumor in a non-invasive fashion. There are many available solutions to tackle cancer using theranostic agents such as photothermal therapy (PTT) and photodynamic therapy (PDT) under the guidance of imaging techniques (e.g., magnetic resonance-MRI, photoacoustic-PA or computed tomography-CT imaging). Additionally, there are several potential theranostic nanoplatforms able to combine diagnosis and therapy at once, such as gold nanoparticles (GNPs), graphene oxide (GO), superparamagnetic iron oxide nanoparticles (SPIONs) and carbon nanodots (CDs). Currently, surface functionalization of these nanoplatforms is an extremely useful protocol for effectively tuning their structures, interface features and physicochemical properties. This approach is much more reliable and amenable to fine adjustment, reaching both physicochemical and regulatory requirements as a function of the specific field of application. Here, we summarize and compare the most promising metal- and carbon-based theranostic tools reported as potential candidates in precision cancer theranostics. We focused our review on the latest developments in surface functionalization strategies for these nanosystems, or hybrid nanocomposites consisting of their combination, and discuss their main characteristics and potential applications in precision cancer medicine.

Temperature Plays an Essential Regulatory Role in the Tumor Immune Microenvironment

In recent years, emerging immunotherapy has been included in various malignant tumor treatment standards. Temperature has been considered to affect different pathophysiological reactions such as inflammation and cancer for a long time. However, in tumor immunology research, temperature is still rarely considered a significant variable. In this review, we discuss the effects of room temperature, body temperature, and the local tumor temperature on the tumor immune microenvironment from multiple levels and perspectives, and we discuss changes in the body's local and whole-body temperature under tumor conditions. We analyze the current use of ablation treatment-the reason for the opposite immune effect. We should pay more attention to the therapeutic potential of temperature and create a better antitumor microenvironment that can be combined with immunotherapy.

Radiofrequency Thermoablation On Ex Vivo Animal Tissues: Changes on Isolated Swine Thyroids

The use of Radiofrequency thermoablation (RFA) for treating large thyroid nodules is limited by the modest efficiency of the available systems in terms of volume of the ablation zones (AZs). This increases the risk of incomplete ablation of the nodule. Systems employing perfused electrodes have been developed to increase the volume of the AZ. Aim of this study is to compare the size of the AZ induced by RFA systems using internally cooled perfused vs. non-perfused electrodes in swine thyroids. RFAs were performed on 40 freshly isolated swine thyroids using both systems. The perfused system was tested using 0.9% saline, 7% and 18% hypertonic saline solutions. Energy delivery to the tissue was stopped when tissue conductivity dropped (real life simulations) and after an established time of 20 seconds (controlled duration). Following RFA, thyroids were transversally and longitudinally cut. Photographs were taken for macroscopic morphometry of the ablated zones before and after formalin fixation, to evaluate tissue shrinkage. Microscopic morphometry was performed on PAS stained sections. In real life simulation experiments, gross morphometry revealed that AZs produced with electrodes perfused using 7.0% saline are larger compared to isotonic saline. Microscopically, all the conditions tested using the perfused system produced larger AZs compared to non-perfused system after 20 seconds of RFA. In conclusion, the perfusion with 7.0% NaCl solution increased the electrical conductivity of the tissue in real life simulations, resulting in larger ablated areas compared to the use of isotonic saline.

A review of ultrasound-mediated microbubbles technology for cancer therapy: a vehicle for chemotherapeutic drug delivery

Background:

The unique behaviour of microbubbles under ultrasound acoustic pressure makes them useful agents for drug and gene delivery. Several studies have demonstrated the potential application of microbubbles as a non-invasive, safe and effective technique for targeted delivery of drugs and genes. The drugs can be incorporated into the microbubbles in several different approaches and then carried to the site of interest where it can be released by destruction of the microbubbles using ultrasound to achieve the required therapeutic effect.

Methods:

The objective of this article is to report on a review of the recent advances of ultrasound-mediated microbubbles as a vehicle for delivering drugs and genes and its potential application for the treatment of cancer.

Conclusion:

Ultrasound-mediated microbubble technology has the potential to significantly improve chemotherapy drug delivery to treatment sites with minimal side effects. Moreover, the technology can induce temporary and reversible changes in the permeability of cells and vessels, thereby allowing for drug delivery in a spatially localised region which can improve the efficiency of drugs with poor bioavailability due to their poor absorption, rapid metabolism and rapid systemic elimination.

The Impact of Focused Ultrasound in Two Tumor Models: Temporal Alterations in the Natural History on Tumor Microenvironment and Immune Cell Response

Image-guided focused ultrasound (FUS) has been successfully employed as an ablative treatment for solid malignancies by exposing immune cells to tumor debris/antigens, consequently inducing an immune response within the tumor microenvironment (TME). To date, immunomodulation effects of non-ablative pulsed-FUS (pFUS) on the TME are poorly understood. In this study, the temporal differences of cytokines, chemokines, and trophic factors (CCTFs) and immune cell populations induced by pFUS were interrogated in murine B16 melanoma or 4T1 breast cancer cells subcutaneously inoculated into C57BL/6 or BALB/c mice. Natural history growth characteristics during the course of 11 days showed a progressive increase in size for both tumors, and proteomic analysis revealed a shift toward an immunosuppressive TME. With respect to tumor natural growth, pFUS applied to tumors on days 1, 5, or 9 demonstrated a decrease in the growth rate 24 h post-sonication. Flow cytometry analysis of tumors, LNs, and Sp, as well as CCTF profiles, relative DNA damage, and adaptive T-cell localization within tumors, demonstrated dynamic innate and adaptive immune-modulation following pFUS in early time points of B16 tumors and in advanced 4T1 tumors. These results provide insight into the temporal dynamics in the treatment-associated TME, which could be used to evaluate an immunomodulatory approach in different tumor types.

The Proteomic Effects of Pulsed Focused Ultrasound on Tumor Microenvironments of Murine Melanoma and Breast Cancer Models

Non-ablative pulsed focused ultrasound (pFUS) targets non-thermal forces that activate local molecular and cellular immune responses. Optimal parameters to stimulate immunotherapeutic tumor microenvironments (TME) and responses in different tumor types remain uninvestigated. Flank B16 murine melanoma and 4T1 breast tumors received 1 MHz pFUS at 1-8 MPa peak negative pressures (PNP) and were analyzed 24 hr post-sonication. Necrosis or hemorrhage were unaltered in both tumors, but pFUS induced DNA strand breaks in tumor cells at PNP ≥6 MPa. pFUS at >4 MPa suppressed anti-inflammatory cytokines in B16 tumors. pFUS to 4T1 tumors decreased anti-inflammatory cytokines and increased pro-inflammatory cytokines and cell adhesion molecules. pFUS at 6 MPa increased calreticulin and alterations in check-point proteins along with tumoral and splenic immune cell changes that could be consistent with a shift towards an anti-TME. pFUS-induced TME alterations shows promise in generating anti-tumor immune responses, but non-uniform responses between tumor types require additional investigation to assess pFUS as a suitable anti-tumor therapy.

Optimization of laser osteotomy at 1064 nm using a graphite topical absorber and a nitrogen assist gas jet

Laser ablation of bone for the purposes of osteotomy is not as well understood as ablation of homogeneous, non-biological materials such as metals and plastics. Ignition times and etch rate can vary during ablation of cortical bone. In this study, we propose the use of two techniques to optimize bone ablation at 1064nm using a coaxial nitrogen jet as an assist gas and topical application of graphite as a highly absorbing chromophore. We show a two order of magnitude reduction in mean time to ignition and variance by using the graphite topical chromophore. We also show that an increase in volumetric flow rate of the assist gas jet does show an initial increase in etch rate, but increased pressure beyond a certain point shows decreased return. This study also demonstrates a 2 ^nd order relationship between exposure time, volumetric flow rate of nitrogen, and etch rate of cortical bone. The results of this study can be used to optimize the performance of laser ablation systems for osteotomy. This is a companion study to an earlier one carried out by Wong et al. [Biomedical Opt. Express6, 1 (2015)].

Dielectric Properties of Ex Vivo Porcine Liver Tissue Characterized at Frequencies Between 5 and 500 kHz When Heated at Different Rates

OBJECTIVE

The released energy during radio frequency thermal ablation therapy changes the dielectric properties of biological tissues. Understanding changes of dielectric properties of biological tissues during heating is fundamental to suitably model the medical procedure. The aim of this work is to obtain the thermal dependences of conductivity and permittivity of ex vivo porcine liver tissue at six frequencies from 5 to 500 kHz, during heating from 37 °C to 100 °C at three heating rates of approximately 0.1, 3, and 10 °C/min.

METHODS

Two experimental setups using different heating sources and a four-needle electrode connected to an impedance analyzer were developed to evaluate the thermal dependencies.

RESULTS

The results at a body temperature of 37 °C show a good agreement with the data reported in the literature. The conductivity initially shows an increase followed by a decrease, whereas the permittivity increases before a subsequent sharp decrease. Above 60 °C, different trends are observed for the three heating rates studied.

CONCLUSION

The electric conductivity and permittivity show a similar behavior at all evaluated frequencies and heating rates. The observed abrupt change of the slope near 45 °C at a slow heating rate may be used to identify the region of reversible changes in the tissue.

SIGNIFICANCE

These results confirm the connection among tissue dielectric properties, working frequency, and exposure time with thermal damage during heating.

A heterogeneous tissue model for treatment planning for magnetic resonance-guided laser interstitial thermal therapy

We evaluated a physics-based model for planning for magnetic resonance-guided laser interstitial thermal therapy for focal brain lesions. Linear superposition of analytical point source solutions to the steady-state Pennes bioheat transfer equation simulates laser-induced heating in brain tissue. The line integral of the photon attenuation from the laser source enables computation of the laser interaction with heterogeneous tissue. Magnetic resonance thermometry data sets (n = 31) were used to calibrate and retrospectively validate the model's thermal ablation prediction accuracy, which was quantified by the Dice similarity coefficient (DSC) between model-predicted and measured ablation regions (T > 57 °C). A Gaussian mixture model was used to identify independent tissue labels on pre-treatment anatomical magnetic resonance images. The tissue-dependent optical attenuation coefficients within these labels were calibrated using an interior point method that maximises DSC agreement with thermometry. The distribution of calibrated tissue properties formed a population model for our patient cohort. Model prediction accuracy was cross-validated using the population mean of the calibrated tissue properties. A homogeneous tissue model was used as a reference control. The median DSC values in cross-validation were 0.829 for the homogeneous model and 0.840 for the heterogeneous model. In cross-validation, the heterogeneous model produced a DSC higher than that produced by the homogeneous model in 23 of the 31 brain lesion ablations. Results of a paired, two-tailed Wilcoxon signed-rank test indicated that the performance improvement of the heterogeneous model over that of the homogeneous model was statistically significant (p < 0.01).

Thermal and mechanical high-intensity focused ultrasound: perspectives on tumor ablation, immune effects and combination strategies

Tumor ablation technologies, such as radiofrequency-, cryo- or high-intensity focused ultrasound (HIFU) ablation will destroy tumor tissue in a minimally invasive manner. Ablation generates large volumes of tumor debris in situ, releasing multiple bio-molecules like tumor antigens and damage-associated molecular patterns. To initiate an adaptive antitumor immune response, antigen-presenting cells need to take up tumor antigens and, following activation, present them to immune effector cells. The impact of the type of tumor ablation on the precise nature, availability and suitability of the tumor debris for immune response induction, however, is poorly understood. In this review, we focus on immune effects after HIFU-mediated ablation and compare these to findings using other ablation technologies. HIFU can be used both for thermal and mechanical destruction of tissue, inducing coagulative necrosis or subcellular fragmentation, respectively. Preclinical and clinical results of HIFU tumor ablation show increased infiltration and activation of CD4⁺ and CD8⁺ T cells. As previously observed for other types of tumor ablation technologies, however, this ablation-induced enhanced infiltration alone appears insufficient to generate consistent protective antitumor immunity. Therapies combining ablation with immune stimulation are therefore expected to be key to boost HIFU-induced immune effects and to achieve systemic, long-lasting, antitumor immunity.

Percutaneous image-guided cryoablation of small renal masses

Renal cell carcinoma is a common malignancy with increasing incidence due to the incidental detection of non-symptomatic small renal masses on imaging. Management of these small tumors has evolved toward minimally invasive nephron-sparing techniques which include partial nephrectomy and image-guided ablation. Cryoablation and radiofrequency ablation are the most utilized ablation modalities with the former more suited for larger and central renal masses due to intra-procedural visualization of the ablation zone and reduced pelvicalyceal injury. In this article, we review the epidemiology and natural history of renal cell carcinoma, the role of biopsy, and the management options available-surgery, image-guided ablation, and active surveillance-with a focus on cryoablation. The clinical outcomes of the longer term maturing cryoablation data are discussed with reference to partial nephrectomy and radiofrequency ablation. Image-guided ablation has often been the management choice in patients deemed unfit for surgery; however, growing evidence from published series demonstrates image-guided ablation as a sound alternative treatment with equivalent oncological outcomes and minimal patient impact.

Interleukin-6 Induced "Acute" Phenotypic Microenvironment Promotes Th1 Anti-Tumor Immunity in Cryo-Thermal Therapy Revealed By Shotgun and Parallel Reaction Monitoring Proteomics

Cryo-thermal therapy has been emerged as a promising novel therapeutic strategy for advanced breast cancer, triggering higher incidence of tumor regression and enhanced remission of metastasis than routine treatments. To better understand its anti-tumor mechanism, we utilized a spontaneous metastatic mouse model and quantitative proteomics to compare N-glycoproteome changes in 94 serum samples with and without treatment. We quantified 231 highly confident N-glycosylated proteins using iTRAQ shotgun proteomics. Among them, 53 showed significantly discriminated regulatory patterns over the time course, in which the acute phase response emerged as the most enhanced pathway. The anti-tumor feature of the acute response was further investigated using parallel reaction monitoring target proteomics and flow cytometry on 23 of the 53 significant proteins. We found that cryo-thermal therapy reset the tumor chronic inflammation to an “acute” phenotype, with up-regulation of acute phase proteins including IL-6 as a key regulator. The IL-6 mediated “acute” phenotype transformed IL-4 and Treg-promoting ICOSL expression to Th1-promoting IFN-γ and IL-12 production, augmented complement system activation and CD86⁺MHCII⁺ dendritic cells maturation and enhanced the proliferation of Th1 memory cells. In addition, we found an increased production of tumor progression and metastatic inhibitory proteins under such “acute” environment, favoring the anti-metastatic effect. Moreover, cryo-thermal on tumors induced the strongest “acute” response compared to cryo/hyperthermia alone or cryo-thermal on healthy tissues, accompanying by the most pronounced anti-tumor immunological effect. In summary, we demonstrated that cryo-thermal therapy induced, IL-6 mediated “acute” microenvironment shifted the tumor chronic microenvironment from Th2 immunosuppressive and pro-tumorigenic to Th1 immunostimulatory and tumoricidal state. Moreover, the magnitude of “acute” and “danger” signals play a key role in determining the efficacy of anti-tumor activity.

Evaluation of the therapeutic efficacy of sequential therapy involving percutaneous microwave ablation in combination with 131I-hypericin using the VX2 rabbit breast solid tumor model

PURPOSE

Combination of percutaneous microwave ablation (PMWA) and intravenous injection of 131I-hypericin(IIIH) may bear potential as a mini-invasive treatment for tumor. The objective of this study was to assess the effect of PMWA and IIIH in breast tumor growth.

METHODS

Ten New Zealand White rabbits bearing VX2 breast carcinomas were randomly divided into two groups (each 5 examples) and processed using PMWA followed by IIIH and IIIH alone. The IIIH activity was evaluated using planar scintigraphy, autoradiography and biodistribution analysis. The maximum effective safe dose of IIIH was found through 48 rabbits with VX2 breast tumor, which were randomized into six groups (n=8 per group). Subsequently, a further 75 rabbits bearing VX2 breast solid tumors were randomly divided into five groups (each 15 examples) and treated as follows: A, no treatment group; B, PMWA alone; C, IIIH alone; D, PMWA+IIIH×1 (at 8 h post-PMWA); and E, PMWA+IIIH×2 (at 8 h and at 8 days post-PMWA). The therapeutic effect was assessed by measurement of tumor size and performation of positron emission tomography/computed tomograph (PET/CT) scans, liver and renal function tests and Kaplan-Meier survival analysis.

RESULTS

The planar scintigraphy findings suggested a significant uptake of 131I in necrotic tumor tissue. The autoradiography gray scales indicated higher selective uptake of IIIH by necrotic tissue, with significant differences between the groups with and those without necrotic tumor tissue (P<0.05). The maximum effective safe dose of IIIH was 1 mCi/kg. The PET/CT scans and tumor size measurement suggested improvements in treatment groups at all time points (P<0.01). Significant differences were detected among Groups A, B, D and E (P<0.05). Lower levels of lung metastasis were detected in Groups D and E (P<0.05). There were no abnormalities in liver and renal functions tests or other reported side effects.

CONCLUSION

IIIH exhibited selective uptake by necrotic tumor tissue. Sequential therapy involving PMWA+IIIH was successfully inhibiting tumor growth and prolonging survival.

Pulmonary radiofrequency ablation (Part 1): current state

The risks involved in surgical treatment and conventional radiotherapy in patients with early lung cancer or lung metastases often make these treatments difficult to justify. However, on the other hand, it is also unacceptable to allow these lesions to evolve freely because, left untreated, these neoplasms will usually lead to the death of the patient. In recent years, alternative local therapies have been developed, such as pulmonary radiofrequency ablation, which has proven to increase survival with a minimal risk of complications. There are common recommendations for these treatments, and although the specific indications for using one technique or another have yet to be established, there are clearly defined situations that will determine the outcome of the treatment. It is important to know these situations, because appropriate patient selection is essential for therapeutic success. This article aims to describe the characteristics and constraints of pulmonary radiofrequency ablation and to outline its role in thoracic oncology in light of the current evidence.

Design and validation of a thermoreversible material for percutaneous tissue hydrodissection

Interventional oncology procedures such as thermal ablation are becoming routine for many cancers. Hydrodissection-separating tissues with fluids-protects tissues near the treatment zone to improve ablation's safety and facilitate more aggressive treatments. However, currently used fluids such as normal saline and 5% dextrose in water (D5W) migrate in the peritoneum, reducing their protective efficacy. As a hydrodissection alternative, we investigated a thermoreversible poloxamer 407 (P407) solution. Such a material can be injected as a liquid which then forms a semi-solid gel at body temperature without syneresis. The desired gelation temperature of 32°C was achieved with 15.4 wt/wt % P407. Viscosity analysis revealed the lowest viscosity and ideal injection point was at 14°C. Solution viscosity increased during gelation, to a peak of 65 kPa*s at 40°C. The electrical impedance of P407 was significantly greater than isotonic saline, but lower than D5W, indicating its potential for electrical protection. The P407 gel was similar to other hydrodissection fluids at ultrasound and CT imaging. Ex vivo liver ablations showed that P407 protects neighboring tissues, but may require a thicker barrier for comparable protection to D5W. Overall, we found that the P407 solution is a feasible alternative to traditional hydrodissection fluids and warrants additional study.

The effects and effectiveness of electromotive drug administration and chemohyperthermia for treating non-muscle invasive bladder cancer

INTRODUCTION

Preliminary studies show that device assisted intravesical therapies appear more effective than passive diffusion intravesical therapy for the treatment of non-muscle invasive bladder cancer (NMIBC) in specific settings, and phase III studies are now being conducted. Consequently, we have undertaken a non-systematic review with the objective of describing the scientific basis and mechanisms of action of electromotive drug administration (EMDA) and chemohyperthermia (CHT).

METHODS

PubMed, ClinicalTrials.gov and the Cochrane Library were searched to source evidence for this non-systematic review. Randomised controlled trials, systematic reviews and meta-analyses were evaluated. Publications regarding the scientific basis and mechanisms of action of EMDA and CHT were identified, as well as clinical studies to date.

RESULTS

EMDA takes advantage of three phenomena: iontophoresis, electro-osmosis and electroporation. It has been found to reduce recurrence rates in NMIBC patients and has been proposed as an addition or alternative to bacillus Calmette-Guérin (BCG) therapy in the treatment of high risk NMIBC. CHT improves the efficacy of mitomycin C by three mechanisms: tumour cell cytotoxicity, altered tumour blood flow and localised immune responses. Fewer studies have been conducted with CHT than with EMDA but they have demonstrated utility for increasing disease-free survival, especially in patients who have previously failed BCG therapy.

CONCLUSIONS

It is anticipated that EMDA and CHT will play important roles in the management of NMIBC in the future. Techniques of delivery should be standardised, and there is a need for more randomised controlled trials to evaluate the benefits of the treatments alongside quality of life and cost-effectiveness.

How to set up a successful tumor ablation practice

Tumor ablation services have increased in prevalence across the country and can now be found in modern health care systems of all sizes. These services have become an integral part of the coordinated multidisciplinary approach to patient care that must take place at any oncologic center of excellence. However, building a reputable tumor ablation practice at an institutional level can be a very difficult task as there are many financial, political, and material considerations that must be addressed during the early phases of operation to ensure its success. This article discusses each of these considerations in turn and provides insight into ways to overcome the inherent challenges faced when bringing all of the necessary elements together to create a thriving tumor ablation practice at an institutional level.

Comparison of percutaneous cryoablation with microwave ablation in a porcine liver model

We compared imaging and pathological changes between argon-helium cryosurgical (AH) and microwave (MW) ablation in a porcine liver model. Immediately after ablation, computed tomography (CT) imaging showed that the area affected by MW ablation was considerably greater than that affected by AH ablation; moreover, the surface area of necrotic tissue was considerably greater in the AH group, whereas the depth of the necrotic area was similar. Seven days after ablation, the affected area had not changed much in the AH group, but it had significantly increased in the MW group; similarly, the surface and depth of the necrotic areas had not changed much in the AH group, but they had increased significantly in the MW group. The pathological findings showed similar definitive areas for both groups at both time points. The findings indicated that long time after both therapies, complete tissue necrosis can be achieved, but the extent and depth of necrosis differ: necrosis foci after AH ablation could be predicted by ice ball under CT image, and necrosis foci after MW ablation will increase obviously. MW ablation might therefore be suitable for tumors with a larger volume and simple anatomical structures, and AH ablation might be suitable for tumors with complex anatomical structures or those located near important organs. These two methods could therefore be used in combination in clinical settings, but details of the procedure need to be studied.

Cryotherapy for local recurrent dermatofibrosarcoma protuberans: experience in 19 patients

Dermatofibrosarcoma protuberans (DFSP) is a locally aggressive, cutaneous, malignant tumor characterized by a high propensity for local relapse. Wide and deep local excision with reconstructive surgery is the current standard therapy for DFSP, with a local recurrence rate (LRR) of nearly 40%. In this study, we cured 19 patients with local recurrence of DFSP with 39 sessions of percutaneous cryoablation performed between July 2004 and August 2008. The LRRs after one, two and three cryosurgery sessions per patient were 68%, 54% and 0%, respectively. Moreover, the LRR did not differ with tumor location or size. Furthermore, all patients had a progression-free survival of >5 years. Only minor complications such as fever, local edema, mild nerve injury and local pain occurred, and were resolved within 1 week with symptomatic treatment. In our experience, percutaneous cryoablation is a relatively safe and efficient technique for the treatment of local recurrence of DFSPs.

Comparative evaluation of percutaneous laser and radiofrequency ablation in patients with HCC smaller than 4 cm

OBJECTIVE

This study was done to compare percutaneous laser ablation (PLA) and radiofrequency thermoablation (RFA) for the treatment of hepatocellular carcinoma (HCC) ≤ 4 cm, in patients with liver cirrhosis.

MATERIALS AND METHODS

Thirty patients with single HCC ≤ 4 cm in diameter were randomly assigned to one of two treatments: 15 patients were treated with PLA, using a multifibre system connected to a neodymium yttrium-aluminium-garnet laser source; 15 patients were treated with RFA, using an expandable needle electrode. Patients were followed up for up to 12 months.

RESULTS

A complete response was obtained in 87 % lesions treated with PLA and in 93 % lesions treated with RFA (p = ns). The overall local recurrence-free survival rates at 3, 6 and 12 months were comparable. However, a higher rate of recurrence was observed in the PLA group for lesions ≥ 21 mm (p = 0.0081). A postablation syndrome was documented in 13 patients (1 PLA; 12 RFA). Tumour necrosis factor-α was significantly higher in the RFA group (p < 0.05).

CONCLUSIONS

RFA is more effective in the treatment of HCC compared to PLA for lesions ≥ 21 mm. However, PLA should be considered a viable treatment option for HCC ≤ 20 mm, in view of the lower incidence of complications.

Optimisation of the coagulation zone for thermal ablation procedures: a theoretical approach with considerations for practical use

PURPOSE

This paper outlines a theoretical approach for optimisation of the coagulation zone for thermal ablation procedures and considerations for its practical application.

METHODS

The theoretical approach is outlined in the Cartesian coordinate system. Considerations for practical application are implemented. The optimised coagulation zone is defined as the bare coverage of tumour mass plus a safety margin. The eccentricity of coagulation centre (ECC) is defined as the distance between the coagulation centre and the tumour centre. The direction of the applicator shaft is determined based on the x-axis direction. The tumour centre and coagulation centre are defined within the x/y-plane. The distance between coagulation margin (applicator tip) and tumour margin is called parallel offset (PAO).

RESULTS

For spherical coagulation shapes, a linear relationship exists between optimised coagulation diameter and ECC. An exponential relationship exists between optimised coagulation volume and ECC. A complex relationship was found between PAO and determinants of ECC, which are ex and ey. PAO is an extremely important parameter, which allows for determination of the optimal applicator tip position in relation to the tumour margin. It can be calculated in such a manner that the optimised coagulation zone is minimised by neutralising dislocation of the coagulation centre in applicator shaft direction. The latter can be realised by withdrawing or further inserting the applicator shaft.

CONCLUSIONS

The presented concept can be used to optimise the extent of the coagulation zone for thermal ablation procedures after positioning of the applicator. Its inherent advantage is the simple adjustment of the applicator shaft, which obviates the need for a repuncture.

Considerations for theoretical modelling of thermal ablation with catheter-based ultrasonic sources: implications for treatment planning, monitoring and control

PURPOSE

To determine the impact of including dynamic changes in tissue physical properties during heating on feedback controlled thermal ablation with catheter-based ultrasound. Additionally, we compared the impact of several indicators of thermal damage on predicted extents of ablation zones for planning and monitoring ablations with this modality.

METHODS

A 3D model of ultrasound ablation with interstitial and transurethral applicators incorporating temperature-based feedback control was used to simulate thermal ablations in prostate and liver tissue. We investigated five coupled models of heat dependent changes in tissue acoustic attenuation/absorption and blood perfusion of varying degrees of complexity. Dimensions of the ablation zone were computed using temperature, thermal dose, and Arrhenius thermal damage indicators of coagulative necrosis. A comparison of the predictions by each of these models was illustrated on a patient-specific anatomy in the treatment planning setting.

RESULTS

Models including dynamic changes in blood perfusion and acoustic attenuation as a function of thermal dose/damage predicted near-identical ablation zone volumes (maximum variation < 2.5%). Accounting for dynamic acoustic attenuation appeared to play a critical role in estimating ablation zone size, as models using constant values for acoustic attenuation predicted ablation zone volumes up to 50% larger or 47% smaller in liver and prostate tissue, respectively. Thermal dose (t(43) ≥ 240 min) and thermal damage (Ω ≥ 4.6) thresholds for coagulative necrosis are in good agreement for all heating durations, temperature thresholds in the range of 54°C for short (<5 min) duration ablations and 50°C for long (15 min) ablations may serve as surrogates for determination of the outer treatment boundary.

CONCLUSIONS

Accounting for dynamic changes in acoustic attenuation/absorption appeared to play a critical role in predicted extents of ablation zones. For typical 5-15 min ablations with this modality, thermal dose and Arrhenius damage measures of ablation zone dimensions are in good agreement, while appropriately selected temperature thresholds provide a computationally cheaper surrogate.

Radiofrequency ablation or percutaneous ethanol injection for the treatment of liver tumors

The liver is a common location of both primary and secondary malignancies. For unresectable liver cancer, many local ablative therapies have been developed. These include e.g., percutaneous ethanol injection (PEI), percutaneous acetic acid injection, radiofrequency ablation (RFA), cryoablation, microwave ablation, laser-induced thermotherapy, and high-intensity focused ultrasound. RFA has recently gained interest and is the most widely applied thermoablative technique. RFA allows more effective tumor control in fewer treatment sessions compared with PEI, but with a higher rate of complications. However, there are certain circumstances where PEI therapy represents a better strategy to control liver tumors than RFA, especially in situations where RFA is difficult, for example when large vessels surround the tumor. In the context of hepatocellular carcinoma (HCC), both RFA and PEI are feasible and of benefit in non-operable patients. RFA seems superior to PEI in HCC > 2 cm, and the combination of interventions may be of benefit in selected patients. Liver resection is superior to RFA for patients with HCC meeting the Milan criteria, but RFA can be employed in tumors ≤ 3 cm and where there is an increased expected operative mortality. In addition, some lines of evidence indicate that RFA and PEI can be employed as a bridge to liver transplantation. The use of RFA in colorectal liver metastases is currently limited to unresectable disease and for patients unfit for surgery. The aim of this article is to summarize the current status of RFA in the management of liver tumors and compare it to the cheap and readily available technique of PEI.

More than just tumor destruction: immunomodulation by thermal ablation of cancer

Over the past decades, thermoablative techniques for the therapy of localized tumors have gained importance in the treatment of patients not eligible for surgical resection. Anecdotal reports have described spontaneous distant tumor regression after thermal ablation, indicating a possible involvement of the immune system, hence an induction of antitumor immunity after thermoinduced therapy. In recent years, a growing body of evidence for modulation of both adaptive and innate immunity, as well as for the induction of danger signals through thermoablation, has emerged. Induced immune responses, however, are mostly weak and not sufficient for the complete eradication of established tumors or durable prevention of disease progression, and combination therapies with immunomodulating drugs are being evaluated with promising results. This article aims to summarize published findings on immune modulation through radiofrequency ablation, cryoablation, microwave ablation therapy, high-intensity focused ultrasound, and laser-induced thermotherapy.