Focused Ultrasound Foundation

This review explores the pivotal role of preanalytical variables in bringing liquid biopsy approaches into the clinic for brain tumors. Preanalytical variables encompass a range of critical issues, from blood sample collection and handling to the impact of tumor heterogeneity and patient-specific factors. These variables introduce challenges such as false positives, false negatives, and variability in the analysis of tumor signals, which can hinder the diagnostic and prognostic utility of liquid biopsies. Understanding the nuances of preanalytical variables is essential for the successful implementation of liquid biopsy in clinical settings. This paper delves into strategies aimed at mitigating the influence of preanalytical variables by emphasizing the importance of standardized sample collection protocols, optimized sample processing and storage, quality control measures, and the integration of multiple liquid biopsy modalities.

Sarcomas are tumors of mesenchymal origin that are generally resistant to systemic therapies and prone to local recurrence despite current multimodal treatment approaches. Focused ultrasound (FUS) is a noninvasive therapeutic technology that may enhance standard treatment strategies for primary solid malignancies. FUS exerts its effects through diverse mechanisms, including high-intensity focused ultrasound (HIFU) thermal ablation, histotripsy, sonodynamic therapy, immunomodulation, and hyperthermia-enhanced drug delivery. In this narrative review, we summarize the mechanisms of focused ultrasound that have been investigated for the treatment of sarcomas and highlight the results of preclinical, veterinary, and clinical studies related to this area.

Chimeric Antigen Receptor T (CAR-T) cell therapy offers substantial promise for the treatment of brain malignancies, yet its clinical translation remains limited. Tumors such as Glioblastoma Multiforme (GBM), Diffuse Intrinsic Pontine Glioma (DIPG), and Medulloblastoma (MB) are associated with poor prognoses and exhibit limited responsiveness to conventional treatment modalities, including radiotherapy, chemotherapy, and surgical resection. The application of CAR-T cell therapy in these contexts faces significant challenges, primarily in terms of efficient cellular trafficking into the tumor microenvironment and access to heterogeneous tumor regions. Furthermore, CAR-T cell persistence, defined by the long-term survival and functionality of infused cells, remains a critical hurdle in achieving durable therapeutic responses and preventing tumor relapses. This review aims to address the two predominant barriers, trafficking and persistence, by discussing the underlying mechanisms that limit CAR-T cell efficacy in brain tumors, reviewing current strategies aimed at overcoming these challenges, and evaluating novel approaches to enhance the effectiveness of CAR-T therapies in this setting.

In 2020, BLOODPAC recommended 11 pre-analytical minimal technical data elements for collection and submission of liquid biopsy data to public databases. This article expands on that work by recommending 22 clinical context and 10 patient context data elements. These elements, essential for liquid biopsy data submitted to repositories like the BLOODPAC Data Commons, cover tumor characteristics, disease progression, and patient demographics, supporting biomarker validation, research, and clinical trials.

Over the past decade, focused ultrasound (FUS) has emerged as a promising therapeutic modality for various medical conditions. However, the exponential growth in the published literature on FUS therapies has made the literature review process increasingly time-consuming, inefficient, and error-prone. Machine learning approaches offer a promising solution to address these challenges. Therefore, the purpose of our study is to (1) explore and compare machine learning techniques for the text classification of scientific abstracts, and (2) integrate these machine learning techniques into the conventional literature review process. A classified dataset of 3588 scientific abstracts related and unrelated to FUS therapies sourced from the PubMed database was used to train various traditional machine learning and deep learning models. The fine-tuned Bio-ClinicalBERT (Bidirectional Encoder Representations from Transformers) model, which we named FusBERT, had comparatively optimal performance metrics with an accuracy of 0.91, a precision of 0.85, a recall of 0.99, and an F1 of 0.91. FusBERT was then successfully integrated into the literature review process. Ultimately, the integration of this model into the literature review pipeline will reduce the number of irrelevant manuscripts that the clinical team must screen, facilitating efficient access to emerging findings in the field.

Glioblastoma (GBM) is the most common and aggressive primary brain tumor. Despite advances in treatment, mechanisms underlying GBM invasion remain incompletely understood. This systematic review synthesizes findings from laboratory and clinical studies to elucidate the molecular mechanisms driving GBM invasion and their implications for prognosis and therapy. This review adhered to PRISMA guidelines, conducting a comprehensive search of PubMed/Medline for studies published up to October 16, 2023. Inclusion criteria focused on studies investigating molecular mechanisms of GBM invasiveness with reported clinical outcomes (overall survival (OS) and progression-free survival (PFS). Exclusion criteria included systematic reviews, case reports, small case series, and studies limited to preclinical data. Risk of bias was assessed using the ROBINS-I tool. From 831 records, 21 studies (2198 patients) met the criteria. Key GBM invasion mechanisms included ECM degradation, vascular invasion, EMT, apoptotic regulation, cytoskeletal organization, and RNA sequencing. Vascular mechanisms were most studied. Bevacizumab resistance linked to poorer outcomes. EMT markers like TWIST and ECM degradation via MMPs such as CD147 correlated with decreased survival. Cytoskeletal and RNA studies highlighted the prognostic significance of tumor subtypes and microenvironmental interactions. This systematic review elucidates the molecular mechanisms underlying GBM invasiveness and their clinical implications. Integrating molecular profiling into routine clinical assessment may enhance prognostic accuracy and therapeutic efficacy, paving the way for personalized treatment strategies.

Focused ultrasound (FUS) is a powerful emerging tool for non-invasive, non-ionizing targeted destruction of tumors. The last two decades have seen a growing body of preclinical and clinical literature supporting the capacity of FUS to increase nascent immune responses to tumors and to potentiate cancer immunotherapies (e.g. checkpoint inhibitors) through a variety of means, including immune modulation and drug delivery. With the rapid acceleration of this field and a multitude of FUS immunotherapy clinical trials having now been deployed worldwide, there is a need to streamline and standardize the methodology for immunological analyses field-wide. Recently, the Focused Ultrasound Foundation and Cancer Research Institute partnered to convene a group of over 85 leaders to discuss the nexus of FUS and immuno-oncology. The guidelines documented herein were assembled in response to recommendations that emerged from this discussion, emphasizing the urgent need for heightened accessibility of immune analysis methods and standardized protocols unique to the field. These guidelines are designated for existing stakeholders in the FUS immuno-oncology domain or those newly entering the field, to provide guidance on collection, storage, and immunological profiling of tissue or blood specimens in the context of FUS immunotherapy studies, and additionally offer templates for standardized deployment of these methods based on collective experience gained within the field to date. These guidelines are tumor-agnostic and provide evidence-based, consensus-based recommendations for both preclinical and clinical immune analysis of tissue and blood specimens.

Boiling histotripsy (BH) is a cavitation-based pulsed focused ultrasound method of mechanical tissue disintegration. When applied to tumor ablation, BH was shown in a number of preclinical studies to stimulate antitumor immune responses, with the extent and dynamics depending on the tumor microenvironment. In this work, we assessed the response of pancreatic ductal adenocarcinoma (PDAC)—an immunologically “cold” tumor—to BH ablation. C57BL/6J mice (n = 6 per group) were bilaterally subcutaneously grafted with KPC-derived mT4 cell line in the hind limbs. When one of the two tumors reached 8 mm, 80% of its volume was ablated with BH (1.5 MHz, 3 ms pulses, 1% duty cycle, 450 W power, 15 pulses/point). The tumors, inguinal lymph nodes and spleens were harvested at 1-, 3-, and 6-day time points and processed for immune phenotyping through flow cytometry, histology, and immunohistochemistry. At earlier time points, the response within the tumor was dominated by neutrophils, and by day 6—by inflammatory monocytes both in treated and contralateral sides versus sham. Transient increases in B cells, neutrophils, NK, NKT cells, and monocytes were observed in the ipsilateral lymph nodes and in spleens on day 3, and mostly subsided by day 6. These data will inform further studies in optimization of combination therapies for PDAC. [Work supported by Focused Ultrasound Foundation.]

In this study, we examine the effects of a recently developed, iron-based coupling medium (IBCM) on guidance magnetic resonance (MR) scans during transcranial, magnetic-resonance-guided, focused ultrasound surgery (tMRgFUS) procedures. More specifically, this study tests the hypotheses that the use of the IBCM will (a) not adversely affect image quality, (b) remove aliasing from small field-of-view scans, and (c) decouple image quality from the motion state of the coupling fluid. An IBCM, whose chemical synthesis and characterization are reported elsewhere, was used as a coupling medium during tMRgFUS procedures on gel phantoms. Guidance magnetization-prepared rapid-gradient-echo (MP-RAGE), TSE, and GRE scans were acquired with fields of view of 28 and 18cm. Experiments were repeated with the IBCM in several distinct flow states. GRE scans were used to estimate temperature time courses as a gel target was insonated. IBCM performance was measured by computing (i) the root mean square difference (RMSD) of TSE and GRE pixel values acquired using water and the IBCM, relative to the use of water; (ii) through-time temperature uncertainty for GRE scans; and (iii) Bland-Altman analysis of the temperature time courses. Finally, guidance TSE and GRE scans of a human volunteer were acquired during a separate sham tMRgFUS procedure. As a control, all experiments were repeated using a water coupling medium. Use of the IBCM reduced RMSD in TSE scans by a factor of 4 or more for all fields of view and nonstationary motion states, but did not reduce RMSD estimates in MP-RAGE scans. With the coupling media in a stationary state, the IBCM altered estimates of temperature uncertainty relative to the use of water by less than 0.2°C. However, with a high flow state, the IBCM reduced temperature uncertainties by the statistically significant amounts (at the 0.01 level) of 0.5°C (28cm field of view) and 5°C (18cm field of view). Bland-Altman analyses found a 0.1°C ± 0.5°C difference between temperature estimates acquired using water and the IBCM as coupling media. Finally, scans of a human volunteer using the IBCM indicate more conspicuous grey/white matter contrast, a reduction in aliasing, and a less than 0.2°C change in temperature uncertainty. The use of an IBCM during tMRgFUS procedures does not adversely affect image quality for TSE and GRE scans, can decouple image quality from the motion state of the coupling fluid, and can remove aliasing from scans where the field of view is set to be much smaller than the spatial extent of the coupling fluid.