Effects of high-intensity focused ultrasound in the treatment of experimental neuroblastoma

Advances of ultrasound in tumor immunotherapy

Immunotherapy has become a revolutionary method for treating tumors, offering new hope to cancer patients worldwide. Immunotherapy strategies such as checkpoint inhibitors, chimeric antigen receptor T-cell (CAR-T) therapy, and cancer vaccines have shown significant potential in clinical trials. Despite the promising results, there are still limitations that impede the overall effectiveness of immunotherapy; the response to immunotherapy is uneven, the response rate of patients is still low, and systemic immune toxicity accompanied with tumor cell immune evasion is common. Ultrasound technology has evolved rapidly in recent years and has become a significant player in tumor immunotherapy. The introductions of high intensity focused ultrasound and ultrasound-stimulated microbubbles have opened doors for new therapeutic strategies in the fight against tumor. This paper explores the revolutionary advancements of ultrasound combined with immunotherapy in this particular field.

Recent advances of ultrasound-responsive nanosystems in tumor immunotherapy

Immunotherapy has revolutionized cancer treatment by boosting the immune system and preventing disease escape mechanisms. Despite its potential, challenges like limited response rates and adverse immune effects impede its widespread clinical adoption. Ultrasound (US), known for its safety and effectiveness in tumor diagnosis and therapy, has been shown to significantly enhance immunotherapy when used with nanosystems. High-intensity focused ultrasound (HIFU) can obliterate tumor cells and elicit immune reactions through the creation of immunogenic debris. Low-intensity focused ultrasound (LIFU) bolsters tumor immunosuppression and mitigates metastasis risk by concentrating dendritic cells. Ultrasonic cavitation (UC) produces microbubbles that can transport immune enhancers directly, thus strengthening the immune response and therapeutic impact. Sonodynamic therapy (SDT) merges nanotechnology with immunotherapy, using specialized sonosensitizers to kill cancer cells and stimulate immune responses, increasing treatment success. This review discusses the integration of ultrasound-responsive nanosystems in tumor immunotherapy, exploring future opportunities and current hurdles.

In-situ tumor vaccination by percutaneous ablative therapy and its synergy with immunotherapeutics: An update on combination therapy

Percutaneous tumor ablation is now a widely accepted minimally invasive local treatment option offered by interventional radiology and applied to various organs and tumor histology types. It utilizes extreme temperatures to achieve irreversible cellular injury, where ablated tumor interacts with surrounding tissue and host via tissue remodeling and inflammation, clinically manifesting as post-ablation syndrome. During this process, in-situ tumor vaccination occurs, in which tumor neoantigens are released from ablated tissue and can prime one’s immune system which would favorably affect both local and remote site disease control. Although successful in priming the immune system, this rarely turns into clinical benefits for local and systemic tumor control due to intrinsic negative immune modulation of the tumor microenvironment. A combination of ablation and immunotherapy has been employed to overcome these and has shown promising preliminary results of synergistic effect without significantly increased risk profiles. The aim of this article is to review the evidence on post-ablation immune response and its synergy with systemic immunotherapies.

Boosting the Immune Response—Combining Local and Immune Therapy for Prostate Cancer Treatment

Due to its slow progression and susceptibility to radical forms of treatment, low-grade PC is associated with high overall survival (OS). With the clinical progression of PC, the therapy is becoming more complex. The immunosuppressive tumor microenvironment (TME) makes PC a difficult target for most immunotherapeutics. Its general immune resistance is established by e.g., immune evasion through Treg cells, synthesis of immunosuppressive mediators, and the defective expression of surface neoantigens. The success of sipuleucel-T in clinical trials initiated several other clinical studies that specifically target the immune escape of tumors and eliminate the immunosuppressive properties of the TME. In the settings of PC treatment, this can be commonly achieved with radiation therapy (RT). In addition, focal therapies usually applied for localized PC, such as high-intensity focused ultrasound (HIFU) therapy, cryotherapy, photodynamic therapy (PDT), and irreversible electroporation (IRE) were shown to boost the anti-cancer response. Nevertheless, the present guidelines restrict their application to the context of a clinical trial or a prospective cohort study. This review explains how RT and focal therapies enhance the immune response. We also provide data supporting the combination of RT and focal treatments with immune therapies.

Focused Ultrasound for Pediatric Diseases

Focused ultrasound (FUS) is a noninvasive therapeutic technology with multiple pediatric clinical applications. The ability of focused ultrasound to target tissues deep in the body without exposing children to the morbidities associated with conventional surgery, interventional procedures, or radiation offers significant advantages. In 2021, there are 10 clinical pediatric focused ultrasound studies evaluating various musculoskeletal, oncologic, neurologic, and vascular diseases of which 8 are actively recruiting and 2 are completed. Pediatric musculoskeletal applications of FUS include treatment of osteoid osteoma and bone metastases using thermal ablation and high-intensity FUS. Pediatric oncologic applications of FUS include treatment of soft tissue tumors including desmoid tumors, malignant sarcomas, and neuroblastoma with high-intensity FUS ablation alone, or in combination with targeted chemotherapy delivery. Pediatric neurologic applications include treatment of benign tumors such as hypothalamic hamartomas with thermal ablation and malignant diffuse intrinsic pontine glioma with low-intensity FUS for blood brain barrier opening and targeted drug delivery. Additionally, low-intensity FUS can be used to treat seizures. Pediatric vascular applications of FUS include treatment of arteriovenous malformations and twin-twin transfusion syndrome using ablation and vascular occlusion. FUS treatment appears safe and efficacious in pediatric populations across many subspecialties. Although there are 7 Food and Drug Administration-approved indications for adult applications of FUS, the first Food and Drug Administration approval for pediatric patients with osteoid osteoma was obtained in 2020. This review summarizes the preclinical and clinical research on focused ultrasound of potential benefit to pediatric populations.

Local Destruction of Tumors and Systemic Immune Effects

Current immune-based therapies signify a major advancement in cancer therapy; yet, they are not effective in the majority of patients. Physically based local destruction techniques have been shown to induce immunologic effects and are increasingly used in order to improve the outcome of immunotherapies. The various local destruction methods have different modes of action and there is considerable variation between the different techniques with respect to the ability and frequency to create a systemic anti-tumor immunologic effect. Since the abscopal effect is considered to be the best indicator of a relevant immunologic effect, the present review focused on the tissue changes associated with this effect in order to find determinants for a strong immunologic response, both when local destruction is used alone and combined with immunotherapy. In addition to the T cell-inflammation that was induced by all methods, the analysis indicated that it was important for an optimal outcome that the released antigens were not destroyed, tumor cell death was necrotic and tumor tissue perfusion was at least partially preserved allowing for antigen presentation, immune cell trafficking and reduction of hypoxia. Local treatment with controlled low level hyperthermia met these requisites and was especially prone to result in abscopal immune activity on its own.

Immunological Effects of Histotripsy for Cancer Therapy

Cancer is the second leading cause of death worldwide despite major advancements in diagnosis and therapy over the past century. One of the most debilitating aspects of cancer is the burden brought on by metastatic disease. Therefore, an ideal treatment protocol would address not only debulking larger primary tumors but also circulating tumor cells and distant metastases. To address this need, the use of immune modulating therapies has become a pillar in the oncology armamentarium. A therapeutic option that has recently emerged is the use of focal ablation therapies that can destroy a tumor through various physical or mechanical mechanisms and release a cellular lysate with the potential to stimulate an immune response. Histotripsy is a non-invasive, non-ionizing, non-thermal, ultrasound guided ablation technology that has shown promise over the past decade as a debulking therapy. As histotripsy therapies have developed, the full picture of the accompanying immune response has revealed a wide range of immunogenic mechanisms that include DAMP and anti-tumor mediator release, changes in local cellular immune populations, development of a systemic immune response, and therapeutic synergism with the inclusion of checkpoint inhibitor therapies. These studies also suggest that there is an immune effect from histotripsy therapies across multiple murine tumor types that may be reproducible. Overall, the effects of histotripsy on tumors show a positive effect on immunomodulation.

Focused Ultrasound for Immunomodulation of the Tumor Microenvironment

Focused ultrasound (FUS) has recently emerged as a modulator of the tumor microenvironment, paving the way for FUS to become a safe yet formidable cancer treatment option. Several mechanisms have been proposed for the role of FUS in facilitating immune responses and overcoming drug delivery barriers. However, with the wide variety of FUS parameters used in diverse tumor types, it is challenging to pinpoint FUS specifications that may elicit the desired antitumor response. To clarify FUS bioeffects, we summarize four mechanisms of action, including thermal ablation, hyperthermia/thermal stress, mechanical perturbation, and histotripsy, each inducing unique vascular and immunological effects. Notable tumor responses to FUS include enhanced vascular permeability, increased T cell infiltration, and tumor growth suppression. In this review, we have categorized and reviewed recent methods of using therapeutic ultrasound to elicit an antitumor immune response with examples that reveal specific solutions and challenges in this new research area.

Molecular targeting therapies for neuroblastoma: Progress and challenges

There is an urgent need to identify novel therapies for childhood cancers. Neuroblastoma is the most common pediatric solid tumor, and accounts for ~15% of childhood cancer‐related mortality. Neuroblastomas exhibit genetic, morphological and clinical heterogeneity, which limits the efficacy of existing treatment modalities. Gaining detailed knowledge of the molecular signatures and genetic variations involved in the pathogenesis of neuroblastoma is necessary to develop safer and more effective treatments for this devastating disease. Recent studies with advanced high‐throughput “omics” techniques have revealed numerous genetic/genomic alterations and dysfunctional pathways that drive the onset, growth, progression, and resistance of neuroblastoma to therapy. A variety of molecular signatures are being evaluated to better understand the disease, with many of them being used as targets to develop new treatments for neuroblastoma patients. In this review, we have summarized the contemporary understanding of the molecular pathways and genetic aberrations, such as those in MYCN, BIRC5, PHOX2B, and LIN28B, involved in the pathogenesis of neuroblastoma, and provide a comprehensive overview of the molecular targeted therapies under preclinical and clinical investigations, particularly those targeting ALK signaling, MDM2, PI3K/Akt/mTOR and RAS‐MAPK pathways, as well as epigenetic regulators. We also give insights on the use of combination therapies involving novel agents that target various pathways. Further, we discuss the future directions that would help identify novel targets and therapeutics and improve the currently available therapies, enhancing the treatment outcomes and survival of patients with neuroblastoma.

Cytoreductive treatment strategies for de novo metastatic prostate cancer

In the past decade, a revolution in the treatment of metastatic prostate cancer has occurred with the advent of novel hormonal agents and life-prolonging chemotherapy regimens in combination with standard androgen-deprivation therapy. Notwithstanding, the use of systemic therapy alone can result in a castrate-resistant state; therefore, increasing focus is being placed on the additional survival benefits that could potentially be achieved with local cytoreductive and/or metastasis-directed therapies. Local treatment of the primary tumour with the established modalities of radiotherapy and radical prostatectomy has been explored in this context, and the use of novel minimally invasive ablative therapies has been proposed. In addition, evidence of the potential clinical benefits of metastasis-directed therapy with ionizing radiation (primarily stereotactic ablative radiotherapy) is accumulating. Herein, we summarize the pathobiological rationale for local cytoreduction and the potentially systemic immunological responses to radiotherapy and ablative therapies in patients with metastatic prostate cancer. We also discuss the current evidence base for a cytoreductive strategy, including metastasis-directed therapy, in the current era of sequential multimodal therapy incorporating novel treatments. Finally, we outline further research questions relating to this complex and evolving treatment landscape.

High intensity focused ultrasound inhibits melanoma cell migration and metastasis through attenuating microRNA-21-mediated PTEN suppression

High intensity focused ultrasound (HIFU) technology is becoming a potential noninvasive treatment for solid tumor. To explore whether HIFU can be applied to treat melanoma and its metastasis, we investigated the effect of HIFU on murine melanoma model. While there was little influence on cell survival, viability or apoptosis, HIFU exposure suppressed melanoma cell migration in vitro and metastasis in vivo. The expression of microRNA-21(miR-21) was down-regulated and PTEN expression was up-regulated in response to HIFU exposure, which was in concomitant with the reduction of AKT activity. Furthermore, ectopic miR-21 expression suppressed this effect of HIFU. These results demonstrate that HIFU exposure can inhibit AKT-mediated melanoma metastasis via miR-21 inhibition to restore PTEN expression. Therefore, targeting the miR-21/PTEN/AKT pathway might be a novel strategy of HIFU in treatment of melanoma.

Emerging Applications of Therapeutic Ultrasound in Neuro-oncology: Moving Beyond Tumor Ablation

: Transcranial focused ultrasound (FUS) can noninvasively transmit acoustic energy with a high degree of accuracy and safety to targets and regions within the brain. Technological advances, including phased-array transducers and real-time temperature monitoring with magnetic resonance thermometry, have created new opportunities for FUS research and clinical translation. Neuro-oncology, in particular, has become a major area of interest because FUS offers a multifaceted approach to the treatment of brain tumors. FUS has the potential to generate cytotoxicity within tumor tissue, both directly via thermal ablation and indirectly through radiosensitization and sonodynamic therapy; to enhance the delivery of therapeutic agents to brain tumors by transiently opening the blood-brain barrier or improving distribution through the brain extracellular space; and to modulate the tumor microenvironment to generate an immune response. In this review, we describe each of these applications for FUS, the proposed mechanisms of action, and the preclinical and clinical studies that have set the foundation for using FUS in neuro-oncology.

ABBREVIATIONS

BBB, blood-brain barrierCED, convection-enhanced delivery5-Ala, 5-aminolevulinic acidFUS, focused ultrasoundGBM, glioblastoma multiformeHSP, heat shock proteinMRgFUS, magnetic resonance-guided focused ultrasoundpFUS, pulsed focused ultrasound.

Focused Ultrasound Immunotherapy for Central Nervous System Pathologies: Challenges and Opportunities

Immunotherapy is rapidly emerging as the cornerstone for the treatment of several forms of metastatic cancer, as well as for a host of other pathologies. Meanwhile, several new high-profile studies have uncovered remarkable linkages between the central nervous and immune systems. With these recent developments, harnessing the immune system for the treatment of brain pathologies is a promising strategy. Here, we contend that MR image-guided focused ultrasound (FUS) represents a noninvasive approach that will allow for favorable therapeutic immunomodulation in the setting of the central nervous system. One obstacle to effective immunotherapeutic drug delivery to the brain is the blood brain barrier (BBB), which refers to the specialized structure of brain capillaries that prevents transport of most therapeutics from the blood into brain tissue. When applied in the presence of circulating microbubbles, FUS can safely and transiently open the BBB to facilitate the delivery of immunotherapeutic agents into the brain parenchyma. Furthermore, it has been demonstrated that physical perturbations of the tissue microenvironment via FUS can modulate immune response in both normal and diseased tissue. In this review article, we provide an overview of FUS energy regimens and corresponding tissue bioeffects, followed by a review of the literature pertaining to FUS for therapeutic antibody delivery in normal brain and preclinical models of brain disease. We provide an overview of studies that demonstrate FUS-mediated immune modulation in both the brain and peripheral settings. Finally, we provide remarks on challenges facing FUS immunotherapy and opportunities for future expansion in this area.

High-Intensity Focused Ultrasound- and Radiation Therapy-Induced Immuno-Modulation: Comparison and Potential Opportunities

In recent years, high-intensity focused ultrasound (HIFU) has emerged as a new and promising non-invasive and non-ionizing ablative technique for the treatment of localized solid tumors. Extensive pre-clinical and clinical studies have evidenced that, in addition to direct destruction of the primary tumor, HIFU-thermoablation may elicit long-term systemic host anti-tumor immunity. In particular, an important consequence of HIFU treatment includes the release of tumor-associated antigens (TAAs), the secretion of immuno-suppressing factors by cancer cells and the induction of cytotoxic T lymphocyte (CTL) activity. Radiation therapy (RT) is the main treatment modality used for many types of tumors and about 50% of all cancer patients receive RT, often used in combination with surgery and chemotherapy. It is well known that RT can modulate anti-tumor immune responses, modifying micro-environment and stimulating inflammatory factors that can greatly affect cell invasion, bystander effects, radiation tissue complications (such as fibrosis), genomic instability and thus, intrinsic cellular radio-sensitivity. To date, various combined therapeutic strategies (such as immuno-therapy) have been performed in order to enhance RT success in treating locally advanced and recurrent tumors. Recent works suggested the combined use of HIFU and RT treatments to increase the tumor cell radio-sensitivity, in order to synergize the effects reaching the maximum results with minimal doses of ionizing radiation (IR). Here, we highlight the opposite immuno-modulation roles of RT and HIFU, providing scientific reasons to test, by experimental approaches, the use of HIFU immune-stimulatory capacity to improve tumor radio-sensitivity, to reduce the RT induced inflammatory response and to decrease the dose-correlated side effects in normal tissues.

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.

Focused ultrasound-aided immunomodulation in glioblastoma multiforme: a therapeutic concept

Patients with glioblastoma multiforme (GBM) exhibit a deficient anti-tumor immune response. Both arms of the immune system were shown to be hampered in GBM, namely the local cellular immunity mediated by the Th₁ subset of helper T cells and the systemic humoral immunity mediated by the Th₂ subset of helper T cells. Immunotherapy is rapidly becoming one of the pillars of anti-cancer therapy. GBM has not received similar clinical successes as of yet, which may be attributed to its relative inaccessibility (the blood-brain barrier (BBB)), its poor immunogenicity, few characterized cancer antigens, or any of the many other immune mechanisms known to be hampered. Focused ultrasound (FUS) is emerging as a promising treatment approach. The effects of FUS on the tissue are not merely thermal. Mounting evidence suggests that in addition to thermal ablation, FUS induces mechanical acoustic cavitation and immunomodulation plays a key role in boosting the host anti-tumor immune responses. We separately discuss the different pertinent immunosuppressive mechanisms harnessed by GBM and the immunomodulatory effects of FUS. The effect of FUS and microbubbles in disrupting the BBB and introducing antigens and drugs to the tumor milieu is discussed. The FUS-induced pro-inflammatory cytokines secretion and stress response, the FUS-induced change in the intra-tumoral immune-cells populations, the FUS-induced augmentation of dendritic cells activity, and the FUS-induced increased cytotoxic cells potency are all discussed. We next attempt at offering a conceptual synopsis of the synergistic treatment of GBM utilizing FUS and immunotherapy. In conclusion, it is increasingly apparent that no single treatment modality will triumph on GBM. The reviewed FUS-induced immunomodulation effects can be harnessed to current and developing immunotherapy approaches. Together, these may overcome GBM-induced immune-evasion and generate a clinically relevant anti-tumor immune response.

Harnessing the immunomodulatory effect of thermal and non-thermal ablative therapies for cancer treatment

Minimally invasive interventional therapies are evolving rapidly and their use for the treatment of solid tumours is becoming more extensive. The in situ destruction of solid tumours by such therapies is thought to release antigens that can prime an antitumour immune response. In this review, we offer an overview of the current evidence for immune response activation associated with the utilisation of the main thermal and non-thermal ablation therapies currently in use today. This is followed by an assessment of the hypothesised mechanisms behind this immune response priming and by a discussion of potential methods of harnessing this specific response, which may subsequently be applicable in the treatment of cancer patients. References were identified through searches of PubMed/MEDLINE and Cochrane databases to identify peer-reviewed original articles, meta-analyses and reviews. Papers were searched from 1850 until October 2014. Articles were also identified through searches of the authors' files. Only papers published in English were reviewed. Thermal and non-thermal therapies have the potential to stimulate antitumour immunity although the current body of evidence is based mostly on murine trials or small-scale phase 1 human trials. The evidence for this immune-modulatory response is currently the strongest in relation to cryotherapy and radiotherapy, although data is accumulating for related ablative treatments such as high-intensity focused ultrasound, radiofrequency ablation and irreversible electroporation. This effect may be greatly enhanced by combining these therapies with other immunostimulatory interventions. Evidence is emerging into the immunomodulatory effect associated with thermal and non-thermal ablative therapies used in cancer treatment in addition to the mechanism behind this effect and how it may be harnessed for therapeutic use. A potential exists for treatment approaches that combine ablation of the primary tumour with control and possible eradication of persistent, locally recurrent and metastatic disease. However, more work is needed into each of these modalities, initially in further animal studies and then subsequently in large-scale prospective human studies.

Ultrasound induced cancer immunotherapy

Recently, the use of ultrasound (US) has been shown to have potential in cancer immunotherapy. High intensity focused US destruction of tumors may lead to immunity forming in situ in the body by immune cells being exposed to the tumor debris and immune stimulatory substances that are present in the tumor remains. Another way of achieving anti-cancer immune responses is by using US in combination with microbubbles and nanobubbles to deliver genes and antigens into cells. US leads to bubble destruction and the forces released to direct delivery of the substances into the cytoplasm of the cells thus circumventing the natural barriers. In this way tumor antigens and antigen-encoding genes can be delivered to immune cells and immune response stimulating genes can be delivered to cancer cells thus enhancing immune responses. Combination of bubbles with cell-targeting ligands and US provides an even more sophisticated delivery system whereby the therapy is not only site specific but also cell specific. In this review we describe how US has been used to achieve immunity and discuss the potential and possible obstacles in future development.

High intensity focused ultrasound ablation and antitumor immune response

The ideal cancer therapy not only induces the death of all localized tumor cells without damage to surrounding normal tissue, but also activates a systemic antitumor immunity. High intensity focused ultrasound (HIFU) has the potential to be such a treatment, as it can non-invasively ablate a targeted tumor below the skin surface, and may subsequently augment host antitumor immunity. This paper is to review increasing pre-clinical and clinical evidence linking antitumor immune response to HIFU ablation, and to discuss the potential mechanisms involved in HIFU-enhanced host antitumor immunity. The seminal studies performed so far indicate that although it is not possible to conclude definitively on the connection between HIFU treatment and antitumor immune response, it is nonetheless important to conduct extensive studies on the subject in order to elucidate the processes involved.

Magnetic resonance-guided focused ultrasound surgery: Part 2: A review of current and future applications

Magnetic resonance-guided focused ultrasound surgery (MRgFUS) is a novel combination of technologies that is actively being realized as a noninvasive therapeutic tool for a myriad of conditions. These applications are reviewed with a focus on neurological use. A combined search of PubMed and MEDLINE was performed to identify the key events and current status of MRgFUS, with a focus on neurological applications. MRgFUS signifies a potentially ideal device for the treatment of neurological diseases. As it is nearly real time, it allows monitored provision of treatment location and energy deposition; is noninvasive, thereby limiting or eliminating disruption of normal tissue; provides focal delivery of therapeutic agents; enhances radiation delivery; and permits modulation of neural function. Multiple clinical applications are currently in clinical use and many more are under active preclinical investigation. The therapeutic potential of MRgFUS is expanding rapidly. Although clinically in its infancy, preclinical and early-phase I clinical trials in neurosurgery suggest a promising future for MRgFUS. Further investigation is necessary to define its true potential and impact.

M-HIFU inhibits tumor growth, suppresses STAT3 activity and enhances tumor specific immunity in a transplant tumor model of prostate cancer

Objective

In this study, we explored the use of mechanical high intensity focused ultrasound (M-HIFU) as a neo-adjuvant therapy prior to surgical resection of the primary tumor. We also investigated the role of signal transducer and activator of transcription 3 (STAT3) in M-HIFU elicited anti-tumor immune response using a transplant tumor model of prostate cancer.

Methods

RM-9, a mouse prostate cancer cell line with constitutively activated STAT3, was inoculated subcutaneously in C57BL/6J mice. The tumor-bearing mice (with a maximum tumor diameter of 5∼6 mm) were treated by M-HIFU or sham exposure two days before surgical resection of the primary tumor. Following recovery, if no tumor recurrence was observed in 30 days, tumor rechallenge was performed. The growth of the rechallenged tumor, survival rate and anti-tumor immune response of the animal were evaluated.

Results

No tumor recurrence and distant metastasis were observed in both treatment groups employing M-HIFU + surgery and surgery alone. However, compared to surgery alone, M-HIFU combined with surgery were found to significantly inhibit the growth of rechallenged tumors, down-regulate intra-tumoral STAT3 activities, increase cytotoxic T cells in spleens and tumor draining lymph nodes (TDLNs), and improve the host survival. Furthermore, M-HIFU combined with surgery was found to significantly decrease the level of immunosuppression with concomitantly increased number and activities of dendritic cells, compared to surgery alone.

Conclusion

Our results demonstrate that M-HIFU can inhibit STAT3 activities, and when combined synergistically with surgery, may provide a novel and promising strategy for the treatment of prostate cancers.

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.

Magnetic resonance guided high-intensity focused ultrasound ablation of musculoskeletal tumors

This article reviews the fundamental principles and clinical experimental uses of magnetic resonance guided high-intensity focused ultrasound (MRgHIFU) ablation of musculoskeletal tumors. MRgHIFU is a noninvasive treatment modality that takes advantage of the ability of magnetic resonance to measure tissue temperature and uses this technology to guide high-intensity focused ultrasound waves to a specific focus within the human body that results in heat generation and complete thermal necrosis of the targeted tissue. Adjacent normal tissues are spared because of the accurate delivery of thermal energy, as well as, local blood perfusion that provides a cooling effect. MRgHIFU is approved by the Food and Drug Administration for the treatment of uterine fibroids and is used on an experimental basis to treat breast, prostate, liver, bone, and brain tumors.

Ultrasound-based combination therapy: potential in urologic cancer

Immune-sensitive urologic malignancies include prostate, kidney and bladder cancers. To date, most immunotherapeutic treatments have been applied to advanced metastatic disease. Limited efficacy in this setting is likely due to an excessive disease burden, which overwhelms the capacity of the immune system. Immunotherapy has not been widely utilized in a low-disease-burden state - a setting in which the immune system may be best suited to effectively mount a clinically meaningful response. The emergence of high-intensity focused ultrasound, and more recently, low-intensity focused ultrasound technologies, have demonstrated not only immune-stimulatory effects but also an interesting capacity to alter tissue architecture and cell membrane properties, which may be exploited to increase tumoral uptake of drugs and vaccines. In this article, we review the literature supporting the novel use of ultrasound combination therapy with adjunctive agents in the treatment of urologic malignancy.

Increased infiltration of activated tumor-infiltrating lymphocytes after high intensity focused ultrasound ablation of human breast cancer

BACKGROUND

Previous studies have shown that high intensity focused ultrasound (HIFU) ablation can induce a distinct inflammatory reaction with marked infiltration of lymphocytes after direct tumor destruction. In this study, we investigated the status of tumor-infiltrating lymphocytes (TILs) after HIFU ablation of human breast cancer and explored mechanisms that may be involved in HIFU-triggered, antitumor immune response.

METHODS

A total of 48 female patients with biopsy-proven breast cancer were divided randomly into 1 of 2 groups: control group (n = 25), in which only modified radical mastectomy was performed, or HIFU group (n = 23), in which HIFU ablation of the primary breast cancer was performed prior to modified radical mastectomy. Using semiquantitative immunohistochemical analysis, tumor-infiltrating T lymphocytes and subsets, B lymphocytes, and natural killer (NK) cells were assessed in all patients. Expression of Fas ligand (FasL), granzyme, and perforin on TILs was also studied in both groups.

RESULTS

TILs infiltrated along the margins of the ablated region in all HIFU-treated neoplasms, and the numbers of tumor-infiltrating CD3, CD4, CD8, CD4/CD8, B lymphocytes, and NK cells was increased significantly in the HIFU group. The number of FasL(+), granzyme(+), and perforin(+) TILs was significantly greater in the HIFU group than in the control group.

CONCLUSION

HIFU ablation induced marked infiltration of CD3, CD4, CD8, B lymphocytes, and NK cells in the treated breast lesions. The number of FasL(+), granzyme(+), and perforin(+) TILs was significantly increased after HIFU treatment.

Activation of tumor-infiltrating antigen presenting cells by high intensity focused ultrasound ablation of human breast cancer

Previous studies have shown that high intensity focused ultrasound (HIFU) ablation can trigger activation of host antitumor responses after direct tumor destruction. The goal of this study was to investigate the status and functions of tumor-infiltrating antigen presenting cells (APCs) after HIFU ablation of human breast cancer, and to explore the mechanisms regarding HIFU-enhanced antitumor response. Forty-eight women with biopsy-proven breast cancer were divided randomly into a control group (n = 25) and a HIFU group (n = 23). Patients in the control group received modified radical mastectomy, and those in the HIFU group underwent HIFU ablation of primary breast cancer, followed by modified radical mastectomy within 1-2 weeks. Using immunohistochemical analysis, tumor-infiltrating dendritic cells (DCs), macrophages, B lymphocytes and expression of HLA-DR and costimulatory molecules on DCs and macrophages were assessed in all patients. The results showed that APCs infiltrated along the margins of the ablated regions in all HIFU-treated tumors, and numbers of tumor-infiltrating DCs, macrophages and B lymphocytes increased significantly in the HIFU group. Compared with the values in the control group, the percentage of DCs and macrophages expressing HLA-DR, CD80 and CD86 was significantly greater in the HIFU group. There were statistically significant differences between numbers of S-100(+) HLA-DR(+), S-100(+) CD80(+), S-100(+) CD86(+), CD68(+) HLA-DR(+), CD68(+) CD80(+) and CD68(+) CD86(+) cells in the control and HIFU groups, respectively. It was concluded that HIFU ablation induces significant infiltration of APCs within the residual tumor debris in patients with breast cancer, and most of the tumor-infiltrating DCs and macrophages were activated after HIFU ablation.

The effect of high intensity focused ultrasound treatment on metastases in a murine melanoma model

This study aims to assess the risk of high intensity focused ultrasound (HIFU) therapy on the incidence of distant metastases and to investigate its association with HIFU-elicited anti-tumor immunity in a murine melanoma (B16-F10) model. Tumor-bearing legs were amputated immediately after or 2 days following HIFU treatment to differentiate the contribution of the elicited anti-tumor immunity. In mice undergoing amputation immediately after mechanical, thermal, or no HIFU treatment, metastasis rates were comparable (18.8%, 13.3%, and 12.5%). In contrast, with a 2-day delay in amputation, the corresponding metastasis rates were 6.7%, 11.8%, and 40%, respectively. Animal survival rate was higher and CTL activity was enhanced in the HIFU treatment groups. Altogether, our results suggest that HIFU treatment does not increase the risk of distant metastasis. Instead, HIFU treatment can elicit an anti-tumor immune response that may be harnessed to improve the overall effectiveness and quality of cancer therapy.

Therapeutic opportunities in biological responses of ultrasound

The therapeutic benefits of several existing ultrasound-based therapies such as facilitated drug delivery, tumor ablation and thrombolysis derive largely from physical or mechanical effects. In contrast, ultrasound can also trigger various time-dependent biochemical responses in the exposed biological milieu. Several biological responses to ultrasound exposure have been previously described in the literature but only a handful of these provide therapeutic opportunities. These include the use of ultrasound for healing of soft tissues and bones, the use of ultrasound for inducing non-necrotic tumor atrophy as well as for potentiation of chemotherapeutic drugs, activation of the immune system, angiogenesis and suppression of phagocytosis. A review of these therapeutic opportunities is presented with particular emphasis on their mechanisms. Overall, this review presents the increasing importance of ultrasound's role as a biological sensitizer enabling novel therapeutic strategies.

Ultrasound mediated delivery of drugs and genes to solid tumors

It has long been shown that therapeutic ultrasound can be used effectively to ablate solid tumors, and a variety of cancers are presently being treated in the clinic using these types of ultrasound exposures. There is, however, an ever-increasing body of preclinical literature that demonstrates how ultrasound energy can also be used non-destructively for increasing the efficacy of drugs and genes for improving cancer treatment. In this review, a summary of the most important ultrasound mechanisms will be given with a detailed description of how each one can be employed for a variety of applications. This includes the manner by which acoustic energy deposition can be used to create changes in tissue permeability for enhancing the delivery of conventional agents, as well as for deploying and activating drugs and genes via specially tailored vehicles and formulations.

Changes in circulating immunosuppressive cytokine levels of cancer patients after high intensity focused ultrasound treatment

Immunosuppression in a patient with malignant tumor is a major obstacle in cancer treatment. In this study, we investigated changes in the circulating level of all measured immunosuppressive cytokines in patients with malignancy before and after high intensity focused ultrasound (HIFU) treatment. Fifteen patients with solid malignancy were enrolled in this study and an enzyme-linked immunoabsorbent assay (ELISA) method was used to measure serum level of vascular endothelial growth factor (VEGF), transforming growth factor-beta1 (TGF-beta1), transforming growth factor-beta2 (TGF-beta2), interleukin 6 (IL-6) and interleukin 10 (IL-10), respectively before and 1 wk after HIFU treatment. Among them, seven patients had distant metastasis and the remaining eight had no metastasis. All patients received one-session HIFU treatment for primary cancer, including complete ablation in eight patients without metastasis, and partial ablation in seven patients with metastases. The results showed that serum immunosuppressive cytokine levels decreased after HIFU treatment, and there were significant decreases of VEGF, TGF-beta1, and TGF-beta2 before and after HIFU treatment. Compared with the values in the metastatic patients, serum levels of immunosuppressive cytokines were significantly lower in the nonmetastatic patients after HIFU treatment. It is concluded that HIFU can decrease tumor-secreted immunosuppressive cytokine production in addition to its direct tumor destruction. This change may lessen tumor-induced immunosuppression and renew antitumor immunity after HIFU in cancer patients.

Influence of the docetaxel administration period (neoadjuvant or concomitant) in relation to HIFU treatment on the growth of Dunning tumors: results of a preliminary study

The objective of this study was to evaluate mechanisms of the synergy between high intensity-focused ultrasound (HIFU) and docetaxel and to determine the best sequence of chemotherapy administration in relation to HIFU treatment for obtaining optimum control of tumoral growth. A total of 15 days after s.c. implantation of the tumor, 52 Copenhagen rats studied were randomized in 4 groups of 13: controls, docetaxel alone (group 1), HIFU and docetaxel concomitant (group 2) and HIFU and docetaxel administered 24 h before treatment (group 3). The number of HIFU shots was calculated in order to cover 75% of the tumor volume. The effects of docetaxel, HIFU and their interaction on tumor volumes were analyzed using a linear regression. The distributions of the tumor volumes were significantly greater in the control group than in the group 1 (P=0.002) and than in both groups 2 and 3 (P < 0.0001 and P = 0.0001). These volumes were also significantly greater in group 1 than in both groups 2 and 3 and there was no difference between the groups 2 and 3. The tumor doubling times were 7.8 days for the group 1, 43.8 days for the group 2, 16.1 days for the group 3 and 5.9 days for the controls. The mechanism of the synergy between HIFU and docetaxel on the growth of Dunning tumors is apparently multifaceted. The results are encouraging because in the two groups of rats treated with the combination of HIFU and docetaxel, the percentage of complete remission was approximately 30%.

Investigation of HIFU-induced anti-tumor immunity in a murine tumor model

Background

High intensity focused ultrasound (HIFU) is an emerging non-invasive treatment modality for localized treatment of cancers. While current clinical strategies employ HIFU exclusively for thermal ablation of the target sites, biological responses associated with both thermal and mechanical damage from focused ultrasound have not been thoroughly investigated. In particular, endogenous danger signals from HIFU-damaged tumor cells may trigger the activation of dendritic cells. This response may play a critical role in a HIFU-elicited anti-tumor immune response which can be harnessed for more effective treatment.

Methods

Mice bearing MC-38 colon adenocarcinoma tumors were treated with thermal and mechanical HIFU exposure settings in order to independently observe HIFU-induced effects on the host's immunological response. In vivo dendritic cell activity was assessed along with the host's response to challenge tumor growth.

Results

Thermal and mechanical HIFU were found to increase CD11c+ cells 3.1-fold and 4-fold, respectively, as compared to 1.5-fold observed for DC injection alone. In addition, thermal and mechanical HIFU increased CFSE+ DC accumulation in draining lymph nodes 5-fold and 10-fold, respectively. Moreover, focused ultrasound treatments not only caused a reduction in the growth of primary tumors, with tumor volume decreasing by 85% for thermal HIFU and 43% for mechanical HIFU, but they also provided protection against subcutaneous tumor re-challenge. Further immunological assays confirmed an enhanced CTL activity and increased tumor-specific IFN-γ-secreting cells in the mice treated by focused ultrasound, with cytotoxicity induced by mechanical HIFU reaching as high as 27% at a 10:1 effector:target ratio.

Conclusion

These studies present initial encouraging results confirming that focused ultrasound treatment can elicit a systemic anti-tumor immune response, and they suggest that this immunity is closely related to dendritic cell activation. Because DC activation was more pronounced when tumor cells were mechanically lysed by focused ultrasound treatment, mechanical HIFU in particular may be employed as a potential strategy in combination with subsequent thermal ablations for increasing the efficacy of HIFU cancer treatment by enhancing the host's anti-tumor immunity.

Host antitumour immune responses to HIFU ablation

The ideal cancer therapy not only induces the death of all localized tumour cells without damage to surrounding normal tissue, but also activates a systemic antitumour immunity. High-intensity focused ultrasound (HIFU) has the potential to be such a treatment, as it can non-invasively ablate a targeted tumour below the skin surface, and may subsequently augment host antitumour immunity. In addition to thermal and cavitation effects, which act directly and locally on the tumour, there is increasing evidence linking systemic anti-tumour immune response to HIFU ablation. This may provide micro-metastatic control and long-term tumour resistance for cancer patients. The goal of this article is to review the emerging pre-clinical and clinical results suggesting that HIFU ablation may enhance host anti-tumour immunity, and to discuss its potential mechanisms. It is concluded that the systemic immune response induced by thermal ablation may play an important role in local recurrence and metastasis control after HIFU treatment.

Magnetic Resonance–Guided Focused Ultrasound Surgery for the Noninvasive Curative Ablation of Tumors and Palliative Treatments: A Review

This article reviews and discusses the up-to-date data on and feasibility of focused ultrasound surgery. This technique uses high-energy ultrasound beams that can be directed to penetrate through the skin and various soft tissues, focus on the target, and destroy tumors by increasing the temperature at the targeted tissue volume. The boundaries of the treatment area are sharply demarcated (focused) without causing damage to the surrounding organs. Although the idea of using sound waves to ablate tumors was first demonstrated in the 1940 s, only recent developments have enabled this technology to become more controlled and, hence, more feasible. The major breakthrough toward its clinical use came with coupling the thermal ablative process to advanced imaging. The development of magnetic resonance as the foundation to guide and evaluate the end results of focused ultrasound surgery treatment, the image guidance of the ultrasound beam, and the development of a reliable method for tissue temperature measurement and real-time feedback of the extent of tissue destruction have pushed this novel technology forward in oncological practice.

Expression of tumor antigens and heat-shock protein 70 in breast cancer cells after high-intensity focused ultrasound ablation

BACKGROUND

Previous results have shown that high-intensity focused ultrasound (HIFU) ablation can potentially activate a host antitumor immunity. The goal of this study was to investigate whether the tumor antigens expressed on breast cancer cells may be preserved after HIFU treatment, and to explore the potential mechanisms regarding the enhanced antitumor response.

METHODS

The primary lesion in 23 patients with biopsy-proven breast cancer were treated with HIFU, then submitted to modified radical mastectomy. By using biotin-streptavidin-peroxidase immunohistochemical technology, a variety of cellular molecules expressed on breast cancer cells, including tumor antigens and heat-shock protein 70 (HSP-70), were stained in all breast specimens. A complete absence of staining was recorded as negative, and immunoreaction of the tumor cells was considered to be positive for antigen expression.

RESULTS

Nuclear positivity of breast cancer cells for proliferating cell nuclear antigen, estrogen receptor, and progesterone receptor was detected in 0%, 9%, and 9% of the treated samples, respectively. The positive rate of cytoplasmic staining for matrix metalloproteinase 9, carbohydrate antigen 15-3, vascular endothelial growth factor, transforming growth factors beta1 and beta2, interleukin 6, and interleukin 10 was 0%, 52%, 30%, 57%, 70%, 48%, and 61% in the treated cancer cells, respectively. The positive rate of cellular membrane staining for epithelial membrane antigen, CD44v6, and HSP-70 was 100%, 0%, and 100% in the zones of treated cancer cells, respectively.

CONCLUSIONS

After HIFU ablation, some tumor antigens remained in the tumor debris. This could provide a potential antigen source to stimulate antitumor immune response.

Potential role of pulsed-high intensity focused ultrasound in gene therapy

As the understanding of human cancer biology increases, new potential strategies for gene therapy are being proposed and evaluated. However, safe and efficient gene transfer continues to be the major hurdle for its implementation in the clinic. Preclinical studies have shown how pulsed-high intensity focused ultrasound (HIFU) exposures can be combined with different modes of administration (local, intravascular and systemic) to improve local delivery of genes and other therapeutic agents. Using image guidance, exposures are given, where short pulses of energy create predominantly mechanical/structural effects in the tissues as opposed to thermal ones. The result is an increase in both extravasation and interstitial diffusion of macromolecules, which occur non-destructively and reversibly. Ultrasound contrast agents can also be added, which enhance acoustic cavitation activity and consequently sonoporation. By being able to locally increase the uptake and expression of DNA, pulsed-HIFU holds much promise to further the use and applications of gene therapy for treating cancer and other pathological conditions.

The safety and feasibility of extracorporeal high-intensity focused ultrasound (HIFU) for the treatment of liver and kidney tumours in a Western population

High-intensity focused ultrasound (HIFU) provides a potential noninvasive alternative to conventional therapies. We report our preliminary experience from clinical trials designed to evaluate the safety and feasibility of a novel, extracorporeal HIFU device for the treatment of liver and kidney tumours in a Western population. The extracorporeal, ultrasound-guided Model-JC Tumor Therapy System (HAIFU Technology Company, China) has been used to treat 30 patients according to four trial protocols. Patients with hepatic or renal tumours underwent a single therapeutic HIFU session under general anaesthesia. Magnetic resonance imaging 12 days after treatment provided assessment of response. The patients were subdivided into those followed up with further imaging alone or those undergoing surgical resection of their tumours, which enabled both radiological and histological assessment. HIFU exposure resulted in discrete zones of ablation in 25 of 27 evaluable patients (93%). Ablation of liver tumours was achieved more consistently than for kidney tumours (100 vs 67%, assessed radiologically). The adverse event profile was favourable when compared to more invasive techniques. HIFU treatment of liver and kidney tumours in a Western population is both safe and feasible. These findings have significant implications for future noninvasive image-guided tumour ablation.

Release of endogenous danger signals from HIFU-treated tumor cells and their stimulatory effects on APCs

The effects of high-intensity focused ultrasound (HIFU) on the release of endogenous danger signals from tumor cells and subsequent activation of antigen-presenting cells (APCs) were evaluated in vitro. MC-38 mouse tumor cells were treated using a 1.1 MHz HIFU transducer under two different protocols (P-=6.7 MPa, 30% duty cycle, 5 s vs. P-=10.7 MPa, 3% duty cycle, 30 s) to produce either thermal necrosis or mechanical lysis of the tumor cells. Here, we report that HIFU treatment can cause the release of endogenous danger signals (ATP and hsp60) and exposure of dendritic cells (DCs) and macrophages to the supernatants of HIFU-treated tumor cells leads to an increased expression of co-stimulatory molecules (CD80 and CD86) with enhanced secretion of IL-12 by the DCs and elevated secretion of TNF-alpha by the macrophages. The potency in APC activation produced by mechanical lysis is much stronger than thermal necrosis of the tumor cells. These findings suggest that optimization of treatment strategy may help to enhance HIFU-elicited anti-tumor immunity.

Synergistic inhibitory effect of high-intensity focused ultrasound combined with chemotherapy on Dunning adenocarcinoma

OBJECTIVE

To evaluate the therapeutic effect of high-intensity focused ultrasound (HIFU) combined with chemotherapy (paclitaxel + estramustine) on AT2 Dunning adenocarcinoma, as no satisfactory treatment for localized prostate cancer is available for patients with a poor prognosis, e.g. stage T3, a high Gleason score, or a prostate-specific antigen level of >15 ng/mL.

MATERIALS AND METHODS

Forty-one Dunning AT2 tumour-bearing Copenhagen rats were divided into four groups, i.e. control, chemotherapy, HIFU, and chemotherapy + HIFU (the last three treated for 1 week). The growth in tumour volume was recorded for 3 weeks, the point at which tumour volume was considered to have doubled (doubling time). The growth curves of each group were plotted and evaluated statistically.

RESULTS

At 30 days of follow-up the distributions of tumour volume with treatment group were significantly different (P < 0.001); volumes were significantly greater in the control than in the chemotherapy-only or in the HIFU-only group (both P = 0.006). The greatest difference was between the chemotherapy + HIFU and the control group. The tumour doubling times were 13.2 days for HIFU-only, 31.2 days for chemotherapy + HIFU and 7.7 days for the controls.

CONCLUSION

These results suggest that this combined therapy could be useful for treating patients with high-risk prostate cancer.

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Biological effects of low intensity ultrasound: the mechanism involved, and its implications on therapy and on biosafety of ultrasound

The biological effects of low intensity ultrasound (US) in vitro; the mechanisms involved; and the factors that can enhance or inhibit these effects are reviewed. The lowest possible US intensities required to induce cell killing or to produce free radicals were determined. Following sonication in the region of these intensities, the effects of US in combination with either hyperthermia, hypotonia, echo-contrast agents (ECA), CO2, incubation time, high cell density or various agents were examined. The results showed that hyperthermia, hypotonia and microbubbles are good enhancers of the bioeffects, while CO2, incubation time and high cell density are good inhibitors. Cellular membrane damage is pivotal in the events leading to cell death, with the cellular damage-and-repair mechanism as an important determinant of the fate of the damaged cells. The optimal level of apoptosis (with minimal lysis) and optimal gene transfection efficiency were attained using a pulsed low intensity US. In summary, the findings suggest that low intensity US is potentially useful in therapy, while on the other hand, they also call for further investigation of such clinical scenarios as high-grade fever, edema or use of ECA which may lead to the lowering of the threshold for bioeffects with diagnostic US.

Activated anti-tumor immunity in cancer patients after high intensity focused ultrasound ablation

T cell-mediated immune responses represent the main cellular antitumor immunity in cancer patients. Recent studies have shown that that both surgical procedure and radiation therapy could cause the functional suppression of lymphocyte-mediated cellular immunity. The purpose of current study is to evaluate whether high intensity focused ultrasound (HIFU) might change a systemic antitumor immunity, particularly T lymphocyte-mediated immunity in cancer patients. A total of 16 patients with solid malignancies were treated with HIFU. Among them, six patients had osteosarcoma (Enneking stage, II(B)4, III(B) 2), five had hepatocellular carcinoma (TNM stage, III 3, IV 2), and five had renal cell carcinoma (TNM stage, III 2, IV 3). Using flow cytometry technique, T lymphocyte and subset, B lymphocyte and natural killer cell (NK) in the peripheral blood were measured in these patients on the day before HIFU and 7 to 10 d after HIFU. The statistical significance of any observed difference is evaluated by Student's t-test. The results showed a significance increase in the population of CD4(+) lymphocytes (p < 0.01) and the ratio of CD4(+) /CD8(+) (p < 0.05) in the circulation of cancer patients after HIFU treatment. The abnormal levels of CD3(+) lymphocytes returned toward the normal range in two patients, CD4(+)/CD8(+) ratio in 3, CD19(+) lymphocytes in one and cytotoxic NK in one, respectively, in comparison to control values. It is concluded that HIFU could enhance a systemic antitumor cellular immunity in addition to local tumor destruction in patients with solid malignancies.

High-intensity focused ultrasound for the treatment of liver tumours

High-intensity focused ultrasound (HIFU) has been investigated as a tool for the treatment of cancer for many decades, but is only now beginning to emerge as a potential alternative to conventional therapies. In recent years, clinical trials have evaluated the clinical efficacy of a number of devices worldwide. In Oxford, UK, we have been using the JC HIFU system (HAIFU Technology Company, Chongqing, PR China) in clinical trials since November 2002. This is the first report of its clinical use outside mainland China. The device is non-invasive, and employs an extracorporeal transducer operating at 0.8-1.6 MHz (aperture 12-15 cm, focal length 9-15 cm), operating clinically at Isp (free field) of 5-15 KWcm(-2). The aims of the trials are to evaluate the safety and performance of the device. Performance is being evaluated through two parallel protocols. One employs radiological assessment of response with the use of follow-up magnetic resonance imaging and microbubble-contrast ultrasound. In the other, histological assessment will be made following elective surgical resection of the HIFU treated tumours. Eleven patients with liver tumours have been treated with HIFU to date. Adverse events include transient pain and minor skin burns. Observed response from the various assessment modalities is discussed.

Preliminary experience using high intensity focused ultrasound for the treatment of patients with advanced stage renal malignancy

PURPOSE

We present the preliminary results of patients with advanced stage renal malignancy treated with high intensity focused ultrasound (HIFU), and investigate the safety and feasibility of using HIFU in the treatment of selected patients with renal tumors.

MATERIALS AND METHODS

HIFU treatment was performed in 12 patients with advanced stage renal cell carcinoma and 1 patient with colon cancer metastasized to kidney. Patients were followed after treatment to observe complications and long-term therapeutic efficacy. Complications and changes in symptoms seen at presentation were recorded. Mid stream urine specimens were sent for microscopy and serum creatinine was measured postoperatively. Followup radiological examinations were performed to detect tumor response to the ablation.

RESULTS

A total of 13 patients received HIFU treatment safely, including 10 who had partial ablation and 3 who had complete tumor ablation. After HIFU hematuria disappeared in 7 of 8 patients and flank pain of presumed malignant origin disappeared in 9 of 10 patients. Postoperative images showed decrease in or absence of tumor blood supply in the treated region and significant shrinkage of the ablated tumor. Of the 13 patients 7 died (median survival 14.1 months, range 2 to 27) and 6 were still alive with median followup of 18.5 months (range 10 to 27).

CONCLUSIONS

This preliminary experience suggests that HIFU could be safe and feasible in the treatment of patients with advanced renal malignancy.

Treatment of uterine leiomyosarcoma in a xenograft nude mouse model using high-intensity focused ultrasound: a potential treatment modality for recurrent pelvic disease

OBJECTIVE

The objective was to test the efficacy of high-intensity focused ultrasound (HIFU) for treatment of uterine leiomyosarcoma in a Xenograft nude mouse model.

METHODS

A total of 65 athymic nude mice were inoculated subcutaneously with 5 to 7 x 10(6) ELT-5B cells, a uterine leiomyosarcoma cell line derived from the Eker rat. Thirty animals showed tumor growth. The tumor volume was measured transcutaneously once a week. Animals were randomly assigned to three groups: HIFU treatment (n = 17), sham treatment (n = 7), and control (n = 6). A HIFU device, operating at a frequency of 2.0 MHz and an intensity of 2000 W/cm(2), was used for treatment.

RESULTS

Within 3 weeks of a single HIFU treatment, 100% reduction in tumor volume was observed in all animals, except one. A second HIFU treatment was applied to that animal, resulting in 100% reduction in tumor volume. The tumors in the sham-treated animals continued to grow at a similar rate to that of the control group to approximately 500% of the tumor volume at the time of treatment. All animals were monitored for a maximum of 3 months. No metastasis was observed in the HIFU-treated animals. Histological examination confirmed a complete tumor disappearance after HIFU treatment.

CONCLUSION

We have shown that HIFU can effectively treat uterine leiomyosarcoma tumors inoculated in Xenograft nude mice, demonstrating HIFU's potential use for treatment of recurrent uterine leiomyosarcoma.