Ultrasound-based combination therapy: potential in urologic cancer

The role of focused ultrasound for pediatric brain tumors: current insights and future implications on treatment strategies

INTRODUCTION

Focused ultrasound (FUS) is an innovative and emerging technology for the treatment of adult and pediatric brain tumors and illustrates the intersection of various specialized fields, including neurosurgery, neuro-oncology, radiation oncology, and biomedical engineering.

OBJECTIVE

The authors provide a comprehensive overview of the application and implications of FUS in treating pediatric brain tumors, with a special focus on pediatric low-grade gliomas (pLGGs) and the evolving landscape of this technology and its clinical utility.

METHODS

The fundamental principles of FUS include its ability to induce thermal ablation or enhance drug delivery through transient blood-brain barrier (BBB) disruption, emphasizing the adaptability of high-intensity focused ultrasound (HIFU) and low-intensity focused ultrasound (LIFU) applications.

RESULTS

Several ongoing clinical trials explore the potential of FUS in offering alternative therapeutic strategies for pathologies where conventional treatments fall short, specifically centrally-located benign CNS tumors and diffuse intrinsic pontine glioma (DIPG). A case illustration involving the use of HIFU for pilocytic astrocytoma is presented.

CONCLUSION

Discussions regarding future applications of FUS for the treatment of gliomas include improved drug delivery, immunomodulation, radiosensitization, and other technological advancements.

Intratumoural immunotherapy plus focal thermal ablation for localized prostate cancer

Major advances have been made in the use of immunotherapy for the treatment of solid tumours, including the use of intratumourally injected immunotherapy instead of systemically delivered immunotherapy. The success of immunotherapy in prostate cancer treatment has been limited to specific populations with advanced disease, which is thought to be a result of prostate cancer being an immunologically 'cold' cancer. Accordingly, combining intratumoural immunotherapy with other treatments that would increase the immunological heat of prostate cancer is of interest. Thermal ablation therapy is currently one of the main strategies used for the treatment of localized prostate cancer and it causes immunological activation against prostate tissue. The use of intratumoural immunotherapy as an adjunct to thermal ablation offers the potential to elicit a systemic and lasting adaptive immune response to cancer-specific antigens, leading to a synergistic effect of combination therapy. The combination of thermal ablation and immunotherapy is currently in the early stages of investigation for the treatment of multiple solid tumour types, and the potential for this combination therapy to also offer benefit to prostate cancer patients is exciting.

Immunomodulation and targeted drug delivery with high intensity focused ultrasound (HIFU): Principles and mechanisms

High intensity focused ultrasound (HIFU) is a non-invasive and non-ionizing sonic energy-based therapeutic technology for inducing thermal and non-thermal effects in tissues. Depending on the parameters, HIFU can ablate tissues by heating them to >55 °C to induce denaturation and coagulative necrosis, improve radio- and chemo-sensitizations and local drug delivery from nanoparticles at moderate hyperthermia (~41-43 °C), and mechanically fragment cells using acoustic cavitation (also known as histotripsy). HIFU has already emerged as an attractive modality for treating human prostate cancer, veterinary cancers, and neuromodulation. Herein, we comprehensively review the role of HIFU in enhancing drug delivery and immunotherapy in soft and calcified tissues. Specifically, the ability of HIFU to improve adjuvant treatments from various classes of drugs is described. These crucial insights highlight the opportunities and challenges of HIFU technology and its potential to support new clinical trials and translation to patients.

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.

Applications of Focused Ultrasound in Cerebrovascular Diseases and Brain Tumors

Oncology and cerebrovascular disease constitute two of the most common diseases afflicting the central nervous system. Standard of treatment of these pathologies is based on multidisciplinary approaches encompassing combination of interventional procedures such as open and endovascular surgeries, drugs (chemotherapies, anti-coagulants, anti-platelet therapies, thrombolytics), and radiation therapies. In this context, therapeutic ultrasound could represent a novel diagnostic/therapeutic in the armamentarium of the surgeon to treat these diseases. Ultrasound relies on mechanical energy to induce numerous physical and biological effects. The application of this technology in neurology has been limited due to the challenges with penetrating the skull, thus limiting a prompt translation as has been seen in treating pathologies in other organs, such as breast and abdomen. Thanks to pivotal adjuncts such as multiconvergent transducers, magnetic resonance imaging (MRI) guidance, MRI thermometry, implantable transducers, and acoustic windows, focused ultrasound (FUS) is ready for prime-time applications in oncology and cerebrovascular neurology. In this review, we analyze the evolution of FUS from the beginning in 1950s to current state-of-the-art. We provide an overall picture of actual and future applications of FUS in oncology and cerebrovascular neurology reporting for each application the principal existing evidences.

Cancer vaccines

Cancer vaccines are designed to promote tumor specific immune responses, particularly cytotoxic CD8 positive T cells that are specific to tumor antigens. The earliest vaccines, which were developed in 1994-95, tested non-mutated, shared tumor associated antigens that had been shown to be immunogenic and capable of inducing clinical responses in a minority of people with late stage cancer. Technological developments in the past few years have enabled the investigation of vaccines that target mutated antigens that are patient specific. Several platforms for cancer vaccination are being tested, including peptides, proteins, antigen presenting cells, tumor cells, and viral vectors. Standard of care treatments, such as surgery and ablation, chemotherapy, and radiotherapy, can also induce antitumor immunity, thereby having cancer vaccine effects. The monitoring of patients' immune responses at baseline and after standard of care treatment is shedding light on immune biomarkers. Combination therapies are being tested in clinical trials and are likely to be the best approach to improving patient outcomes.

High-intensity focused ultrasound: advances in technology and experimental trials support enhanced utility of focused ultrasound surgery in oncology

High-intensity focused ultrasound (HIFU) is a rapidly maturing technology with diverse clinical applications. In the field of oncology, the use of HIFU to non-invasively cause tissue necrosis in a defined target, a technique known as focused ultrasound surgery (FUS), has considerable potential for tumour ablation. In this article, we outline the development and underlying principles of HIFU, overview the limitations and commercially available equipment for FUS, then summarise some of the recent technological advances and experimental clinical trials that we predict will have a positive impact on extending the role of FUS in cancer therapy.

Focal therapy for localised unifocal and multifocal prostate cancer: a prospective development study

Background

Radical whole-gland therapy can lead to significant genitourinary and rectal side-effects for men with localised prostate cancer. We report on whether selective focal ablation of unifocal and multifocal cancer lesions can reduce this treatment burden.

Methods

Men aged 45–80 years were eligible for this prospective development study if they had low-risk to high-risk localised prostate cancer (prostate specific antigen [PSA] ≤15 ng/mL, Gleason score ≤4 + 3, stage ≤T2), with no previous androgen deprivation or treatment for prostate cancer, and who could safely undergo multiparametric MRI and have a general anaesthetic. Patients received focal therapy using high-intensity focused ultrasound, delivered to all known cancer lesions, with a margin of normal tissue, identified on multiparametric MRI, template prostate-mapping biopsies, or both. Primary endpoints were adverse events (serious and otherwise) and urinary symptoms and erectile function assessed using patient questionnaires. Analyses were done on a per-protocol basis. This study is registered with ClinicalTrials.gov, number NCT00561314.

Findings

42 men were recruited between June 27, 2007, and June 30, 2010; one man died from an unrelated cause (pneumonia) 3 months after treatment and was excluded from analyses. After treatment, one man was admitted to hospital for acute urinary retention, and another had stricture interventions requiring hospital admission. Nine men (22%, 95% CI 11–38) had self-resolving, mild to moderate, intermittent dysuria (median duration 5·0 days [IQR 2·5–18·5]). Urinary debris occurred in 14 men (34%, 95% CI 20–51), with a median duration of 14·5 days (IQR 6·0–16·5). Urinary tract infection was noted in seven men (17%, 95% CI 7–32). Median overall International Index of Erectile Function-15 (IIEF-15) scores were similar at baseline and at 12 months (p=0·060), as were median IIEF-15 scores for intercourse satisfaction (p=0·454), sexual desire (p=0·644), and overall satisfaction (p=0·257). Significant deteriorations between baseline and 12 months were noted for IIEF-15 erectile (p=0·042) and orgasmic function (p=0·003). Of 35 men with good baseline function, 31 (89%, 95% CI 73–97) had erections sufficient for penetration 12 months after focal therapy. Median UCLA Expanded Prostate Cancer Index Composite (EPIC) urinary incontinence scores were similar at baseline as and 12 months (p=0·045). There was an improvement in lower urinary tract symptoms, assessed by International Prostate Symptom Score (IPSS), between baseline and 12 months (p=0·026), but the IPSS-quality of life score showed no difference between baseline and 12 months (p=0·655). All 38 men with no baseline urinary incontinence were leak-free and pad-free by 9 months. All 40 men pad-free at baseline were pad-free by 3 months and maintained pad-free continence at 12 months. No significant difference was reported in median Trial Outcomes Index scores between baseline and 12 months (p=0·113) but significant improvement was shown in median Functional Assessment of Cancer Therapy (FACT)-Prostate (p=0·045) and median FACT-General scores (p=0·041). No histological evidence of cancer was identified in 30 of 39 men biopsied at 6 months (77%, 95% CI 61–89); 36 (92%, 79–98) were free of clinically significant cancer. After retreatment in four men, 39 of 41 (95%, 95% CI 83–99) had no evidence of disease on multiparametric MRI at 12 months.

Interpretation

Focal therapy of individual prostate cancer lesions, whether multifocal or unifocal, leads to a low rate of genitourinary side-effects and an encouraging rate of early absence of clinically significant prostate cancer.

Funding

Medical Research Council (UK), Pelican Cancer Foundation, and St Peters Trust.