Preclinical imaging of epidermal growth factor receptor with ABY-029 in soft-tissue sarcoma for fluorescence-guided surgery and tumor detection

In Vivo Labeling and Detection of Circulating Tumor Cells in Mice Using OTL38

PURPOSE

We recently developed an optical instrument to non-invasively detect fluorescently labeled circulating tumor cells (CTCs) in mice called 'Diffuse in vivo Flow Cytometry' (DiFC). OTL38 is a folate receptor (FR) targeted near-infrared (NIR) contrast agent that is FDA approved for use in fluorescence guided surgery of ovarian and lung cancer. In this work, we investigated the use OTL38 for in vivo labeling and detection of FR + CTCs with DiFC.

PROCEDURES

We tested OTL38 labeling of FR + cancer cell lines (IGROV-1 and L1210A) as well as FR- MM.1S cells in suspensions of Human Peripheral Blood Mononuclear cells (PBMCs) in vitro. We also tested OTL38 labeling and NIR-DIFC detection of FR + L1210A cells in blood circulation in nude mice in vivo.

RESULTS

62% of IGROV-1 and 83% of L1210A were labeled above non-specific background levels in suspensions of PBMCs in vitro compared to only 2% of FR- MM.1S cells. L1210A cells could be labeled with OTL38 directly in circulation in vivo and externally detected using NIR-DiFC in mice with low false positive detection rates.

CONCLUSIONS

This work shows the feasibility of labeling CTCs in vivo with OTL38 and detection with DiFC. Although further refinement of the DiFC instrument and signal processing algorithms and testing with other animal models is needed, this work may eventually pave the way for human use of DiFC.

Neoadjuvant Therapies Do Not Reduce Epidermal Growth Factor Receptor (EGFR) Expression or EGFR-Targeted Fluorescence in a Murine Model of Soft-Tissue Sarcomas

PURPOSE

ABY-029, an epidermal growth factor receptor (EGFR)-targeted, synthetic Affibody peptide labeled with a near-infrared fluorophore, is under investigation for fluorescence-guided surgery of sarcomas. To date, studies using ABY-029 have occurred in tumors naïve to chemotherapy (CTx) and radiation therapy (RTx), although these neoadjuvant therapies are frequently used for sarcoma treatment in humans. The goal of this study was to evaluate the impact of CTx and RTx on tumor EGFR expression and ABY-029 fluorescence of human soft-tissue sarcoma xenografts in a murine model.

PROCEDURES

Immunodeficient mice (n = 98) were divided into five sarcoma xenograft groups and three treatment groups - CTx only, RTx only, and CTx followed by RTx, plus controls. Four hours post-injection of ABY-029, animals were sacrificed followed by immediate fluorescence imaging of ex vivo adipose, muscle, nerve, and tumor tissues. Histological hematoxylin and eosin staining confirmed tumor type, and immunohistochemistry staining determined EGFR, cluster of differentiation 31 (CD31), and smooth muscle actin (SMA) expression levels. Correlation analysis (Pearson's correlation coefficients, r) and linear regression (unstandardized coefficient estimates, B) were used to determine statistical relationships in molecular expression and tissue fluorescence between xenografts and treatment groups.

RESULTS

Neoadjuvant therapies had no broad impact on EGFR expression (|B|≤ 7.0, p ≥ 0.4) or on mean tissue fluorescence (any tissue type, (|B|≤ 2329.0, p ≥ 0.1). Mean tumor fluorescence was significantly related to EGFR expression (r = 0.26, p = 0.01), as expected.

CONCLUSION

Results suggest that ABY-029 as an EGFR-targeted, fluorescent probe is not negatively impacted by neoadjuvant soft-tissue sarcoma therapies, although validation in humans is required.

What is the diagnostic accuracy of fluorescence-guided surgery for margin assessment in appendicular bone and soft tissue tumors? - A systematic review of clinical studies

BACKGROUND

Fluorescence-guided surgery (FGS) is a novel technique to successfully assess surgical margins intraoperatively. Investigation and adoption of this technique in orthopaedic oncology remains limited.

METHODS

The PRISMA guidelines were followed for this manuscript. Our study was registered on PROSPERO (380520). Studies describing the use of FGS for resection of bone and soft tissue sarcomas (STS) on humans were included. Diagnostic performance metrics (sensitivity, specificity, positive predictive value [PPV], negative predictive value [NPV] and accuracy) and margin positivity rate were the outcomes assessed.

RESULTS

Critical appraisal using the Joanna Brigs Institute checklists showed significant concerns for study quality. Sensitivity of FGS ranged from 22.2 % to 100 % in three of the four studies assessing his metrics; one study in appendicular tumors in the pediatric population reported 0 % sensitivity in the three cases included. Specificity ranged from 9.38 % to 100 %. PPV ranged from 14.6 % to 70 % while NPV was between 53.3 % and 100 %. The diagnostic accuracy ranged from 21.62 % to 92.31 %. Margin positivity rate ranged from 2 % to 50 %, with six of the seven studies reporting values between 20 % and 50 %.

CONCLUSIONS

FSG is a feasible technique to assess tumor margins in bone and STS. Reported performance metrics and margin positivity rates vary widely between studies due to low study quality and high heterogeneity in dying protocols.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Fluorescence lifetime of injected indocyanine green as a universal marker of solid tumours in patients

The surgical resection of solid tumours can be enhanced by fluorescence-guided imaging. However, variable tumour uptake and incomplete clearance of fluorescent dyes reduces the accuracy of distinguishing tumour from normal tissue via conventional fluorescence intensity-based imaging. Here we show that, after systemic injection of the near-infrared dye indocyanine green in patients with various types of solid tumour, the fluorescence lifetime (FLT) of tumour tissue is longer than the FLT of non-cancerous tissue. This tumour-specific shift in FLT can be used to distinguish tumours from normal tissue with an accuracy of over 97% across tumour types, and can be visualized at the cellular level using microscopy and in larger specimens through wide-field imaging. Unlike fluorescence intensity, which depends on imaging-system parameters, tissue depth and the amount of dye taken up by tumours, FLT is a photophysical property that is largely independent of these factors. FLT imaging with indocyanine green may improve the accuracy of cancer surgeries.

Safety assessment of fluorescently labeled anti-EGFR Nanobodies in healthy dogs

Introduction: Surgical resection is one of the main treatment options for several types of cancer, the desired outcome being complete removal of the primary tumor and its local metastases. Any malignant tissue that remains after surgery may lead to relapsing disease, negatively impacting the patient's quality of life and overall survival. Fluorescence imaging in surgical oncology aims to facilitate full resection of solid tumors through the visualization of malignant tissue during surgery, following the administration of a fluorescent contrast agent. An important class of targeting molecules are Nanobodies® (Nbs), small antigen-binding fragments derived from camelid heavy chain only antibodies. When coupled with a fluorophore, Nbs can bind to a specific receptor and demarcate tumor margins through a fluorescence camera, improving the accuracy of surgical intervention. A widely investigated target for fluorescence-guided surgery is the epidermal growth factor receptor (EGFR), which is overexpressed in several types of tumors. Promising results with the fluorescently labeled anti-EGFR Nb 7D12-s775z in murine models motivated a project employing the compound in a pioneering study in dogs with spontaneous cancer. Methods: To determine the safety profile of the study drug, three healthy purpose-bred dogs received an intravenous injection of the tracer at 5.83, 11.66, and 19.47 mg/m2, separated by a 14-day wash-out period. Physical examination and fluorescence imaging were performed at established time points, and the animals were closely monitored between doses. Blood and urine values were analyzed pre- and 24 h post administration. Results: No adverse effects were observed, and blood and urine values stayed within the reference range. Images of the oral mucosa, acquired with a fluorescence imaging device (Fluobeam®), suggest rapid clearance, which was in accordance with previous in vivo studies. Discussion: These are the first results to indicate that 7D12-s775z is well tolerated in dogs and paves the way to conduct clinical trials in canine patients with EGFR-overexpressing spontaneous tumors.

Paired-agent imaging as a rapid en face margin screening method in Mohs micrographic surgery

Background

Mohs micrographic surgery is a procedure used for non-melanoma skin cancers that has 97-99% cure rates largely owing to 100% margin analysis enabled by en face sectioning with real-time, iterative histologic assessment. However, the technique is limited to small and aggressive tumors in high-risk areas because the histopathological preparation and assessment is very time intensive. To address this, paired-agent imaging (PAI) can be used to rapidly screen excised specimens and identify tumor positive margins for guided and more efficient microscopic evaluation.

Methods

A mouse xenograft model of human squamous cell carcinoma (n = 8 mice, 13 tumors) underwent PAI. Targeted (ABY-029, anti-epidermal growth factor receptor (EGFR) affibody molecule) and untargeted (IRDye 680LT carboxylate) imaging agents were simultaneously injected 3-4 h prior to surgical tumor resection. Fluorescence imaging was performed on main, unprocessed excised specimens and en face margins (tissue sections tangential to the deep margin surface). Binding potential (BP) - a quantity proportional to receptor concentration - and targeted fluorescence signal were measured for each, and respective mean and maximum values were analyzed to compare diagnostic ability and contrast. The BP and targeted fluorescence of the main specimen and margin samples were also correlated with EGFR immunohistochemistry (IHC).

Results

PAI consistently outperformed targeted fluorescence alone in terms of diagnostic ability and contrast-to-variance ratio (CVR). Mean and maximum measures of BP resulted in 100% accuracy, while mean and maximum targeted fluorescence signal offered 97% and 98% accuracy, respectively. Moreover, maximum BP had the greatest average CVR for both main specimen and margin samples (average 1.7 ± 0.4 times improvement over other measures). Fresh tissue margin imaging improved similarity with EGFR IHC volume estimates compared to main specimen imaging in line profile analysis; and margin BP specifically had the strongest concordance (average 3.6 ± 2.2 times improvement over other measures).

Conclusions

PAI was able to reliably distinguish tumor from normal tissue in fresh en face margin samples using the single metric of maximum BP. This demonstrated the potential for PAI to act as a highly sensitive screening tool to eliminate the extra time wasted on real-time pathological assessment of low-risk margins.

Fluorescence guidance improves the accuracy of radiological imaging-guided surgical navigation

BACKGROUND

Imaging-based navigation technologies require static referencing between the target anatomy and the optical sensors. Imaging-based navigation is therefore well suited to operations involving bony anatomy; however, these technologies have not translated to soft-tissue surgery. We sought to determine if fluorescence imaging complement conventional, radiological imaging-based navigation to guide the dissection of soft-tissue phantom tumors.

METHODS

Using a human tissue-simulating model, we created tumor phantoms with physiologically accurate optical density and contrast concentrations. Phantoms were dissected using all possible combinations of computed tomography (CT), magnetic resonance, and fluorescence imaging; controls were included. The data were margin accuracy, margin status, tumor spatial alignment, and dissection duration.

RESULTS

Margin accuracy was higher for combined navigation modalities compared to individual navigation modalities, and accuracy was highest with combined CT and fluorescence navigation (p = 0.045). Margin status improved with combined CT and fluorescence imaging.

CONCLUSIONS

At present, imaging-based navigation has limited application in guiding soft-tissue tumor operations due to its inability to compensate for positional changes during surgery. This study indicates that fluorescence guidance enhances the accuracy of imaging-based navigation and may be best viewed as a synergistic technology, rather than a competing one.

Improved Discrimination of Tumors with Low and Heterogeneous EGFR Expression in Fluorescence-Guided Surgery Through Paired-Agent Protocols

PURPOSE

The goal of fluorescence-guided surgery (FGS) in oncology is to improve the surgical therapeutic index by enhancing contrast between cancerous and healthy tissues. However, optimal discrimination between these tissues is complicated by the nonspecific uptake and retention of molecular targeted agents and the variance of fluorescence signal. Paired-agent imaging (PAI) employs co-administration of an untargeted imaging agent with a molecular targeted agent, providing a normalization factor to minimize nonspecific and varied signals. The resulting measured binding potential is quantitative and equivalent to in vivo immunohistochemistry of the target protein. This study demonstrates that PAI improves the accuracy of tumor-to-healthy tissue discrimination compared to single-agent imaging for in vivo FGS.

PROCEDURES

PAI using a fluorescent anti-epidermal growth factor receptor (EGFR) affibody molecule (ABY-029, eIND 122,681) with untargeted IRDye 700DX carboxylate was compared to ABY-029 alone in an oral squamous cell carcinoma xenograft mouse model at 3 h after dye administration (n = 30).

RESULTS

PAI significantly enhanced tumor discrimination, as compared to ABY-029 alone in low EGFR-expressing tumors and highly heterogeneous populations including multiple cell lines with varying expression (diagnostic accuracy: 0.908 vs. 0.854 and 0.908 vs. 0.822; and ROC curve AUC: 0.963 vs. 0.909 and 0.957 vs. 0.909, respectively) indicating a potential for universal FGS image thresholds to determine surgical margins. In addition, PAI achieved significantly higher diagnostic ability than ABY-029 alone 0.25-5-h post injection and exhibited a stronger correlation to EGFR expression heterogeneity.

CONCLUSION

The quantitative receptor delineation of PAI promises to improve the surgical therapeutic index of cancer resection in a clinically relevant timeline.

Current and Future Applications of Fluorescence Guidance in Orthopaedic Surgery

Fluorescence-guided surgery (FGS) is an evolving field that seeks to identify important anatomic structures or physiologic phenomena with helpful relevance to the execution of surgical procedures. Fluorescence labeling occurs generally via the administration of fluorescent reporters that may be molecularly targeted, enzyme-activated, or untargeted, vascular probes. Fluorescence guidance has substantially changed care strategies in numerous surgical fields; however, investigation and adoption in orthopaedic surgery have lagged. FGS shows the potential for improving patient care in orthopaedics via several applications including disease diagnosis, perfusion-based tissue healing capacity assessment, infection/tumor eradication, and anatomic structure identification. This review highlights current and future applications of fluorescence guidance in orthopaedics and identifies key challenges to translation and potential solutions.

Intraoperative Evaluation of Soft Tissue Sarcoma Surgical Margins with Indocyanine Green Fluorescence Imaging

Soft tissue sarcomas (STS) are rare malignant tumors often associated with poor outcomes and high local recurrence rates. Current tools for intraoperative and definitive margin assessment include intraoperative frozen section and permanent pathology, respectively. Indocyanine green dye (ICG) is a historically safe fluorophore dye that has demonstrated efficacy for intraoperative margin assessment in the surgical management of both breast and gastrointestinal cancers. The utility of ICG in the surgical management of sarcoma surgery has primarily been studied in pre-clinical mouse models and warrants further investigation as a potential adjunct to achieving negative margins. This study is a prospective, non-randomized clinical study conducted on patients with confirmed or suspected STS. Patients younger than 18 years, with a prior adverse reaction to iodine or fluorescein, or with renal disease were excluded from the study. Intravenous ICG was infused approximately three hours prior to surgery at a dosage of 2.0-2.5 mg/kg, and following tumor resection, the excised tumor and tumor bed were imaged for fluorescence intensity. When scanning the tumor bed, a threshold of 77% calibrated to the region of maximum intensity in the resected tumor was defined as a positive ICG margin, according to published protocols from the breast cancer literature. ICG results were then compared with the surgeon's clinical impression of margin status and permanent pathology results. Out of 26 subjects recruited for the original study, 18 soft tissue sarcomas (STS) were included for analysis. Three subjects were excluded for having bone sarcomas, and five subjects were excluded due to final pathology, which was ultimately inconsistent with sarcoma. The average age of patients was 64.1 years old (range: 28-83), with an average ICG dose of 201.8 mg. In 56% (10/18) of patients, ICG margins were consistent with the permanent pathology margins, with 89% specificity. The use of ICG as an intraoperative adjunct to obtaining negative margins in soft tissue sarcoma surgery is promising. However, studies with larger sample sizes are warranted to further delineate the accuracy, optimal dosage, timing, and types of sarcoma in which this diagnostic tool may be most useful.

First Clinical Results of Fluorescence Lifetime-enhanced Tumor Imaging Using Receptor-targeted Fluorescent Probes

PURPOSE

Fluorescence molecular imaging, using cancer-targeted near infrared (NIR) fluorescent probes, offers the promise of accurate tumor delineation during surgeries and the detection of cancer specific molecular expression in vivo. However, nonspecific probe accumulation in normal tissue results in poor tumor fluorescence contrast, precluding widespread clinical adoption of novel imaging agents. Here we present the first clinical evidence that fluorescence lifetime (FLT) imaging can provide tumor specificity at the cellular level in patients systemically injected with panitumumab-IRDye800CW, an EGFR-targeted NIR fluorescent probe.

EXPERIMENTAL DESIGN

We performed wide-field and microscopic FLT imaging of resection specimens from patients injected with panitumumab-IRDye800CW under an FDA directed clinical trial.

RESULTS

We show that the FLT within EGFR-overexpressing cancer cells is significantly longer than the FLT of normal tissue, providing high sensitivity (>98%) and specificity (>98%) for tumor versus normal tissue classification, despite the presence of significant nonspecific probe accumulation. We further show microscopic evidence that the mean tissue FLT is spatially correlated (r > 0.85) with tumor-specific EGFR expression in tissue and is consistent across multiple patients. These tumor cell-specific FLT changes can be detected through thick biological tissue, allowing highly specific tumor detection and noninvasive monitoring of tumor EFGR expression in vivo.

CONCLUSIONS

Our data indicate that FLT imaging is a promising approach for enhancing tumor contrast using an antibody-targeted NIR probe with a proven safety profile in humans, suggesting a strong potential for clinical applications in image guided surgery, cancer diagnostics, and staging.

Assessment and Comparison of Three Dimensional Exoscopes for Near-Infrared Fluorescence-Guided Surgery using Second-Window Indocyanine-Green

Objective

Compared to microscopes, exoscopes have advantages in field-depth, ergonomics, and educational value. Exoscopes are especially well-poised for adaptation into fluorescence-guided surgery (FGS) due to their excitation source, light path, and image processing capabilities. We evaluated the feasibility of near-infrared FGS using a 3-dimensional (3D), 4 K exoscope with near-infrared fluorescence imaging capability. We then compared it to the most sensitive, commercially-available near-infrared exoscope system (3D and 960 p). In-vitro and intraoperative comparisons were performed.

Methods

Serial dilutions of indocyanine-green (1–2000 μg/mL) were imaged with the 3D, 4 K Olympus Orbeye (system 1) and the 3D, 960 p VisionSense Iridium (system 2). Near-infrared sensitivity was calculated using signal-to-background ratios (SBRs). In addition, three patients with brain tumors were administered indocyanine-green and imaged with system 1, with two also imaged with system 2 for comparison.

Results

Systems 1 and 2 detected near-infrared fluorescence from indocyanine green concentrations of >250 μg/L and >31.3 μg/L, respectively. Intraoperatively, system 1 visualized strong near-infrared fluorescence from two, strongly gadolinium-enhancing meningiomas (SBR=2.4, 1.7). The high-resolution, bright images were sufficient for the surgeon to appreciate the underlying anatomy in the near-infrared mode. However, system 1 was not able to visualize fluorescence from a weakly-enhancing intraparenchymal metastasis. In contrast, system 2 successfully visualized both the meningioma and the metastasis but lacked high resolution stereopsis.

Conclusion

Three-dimensional exoscope systems provide an alternative visualization platform for both standard microsurgery and near-infrared fluorescent guided surgery. However, when tumor fluorescence is weak (i.e., low fluorophore uptake, deep tumors), highly sensitive near-infrared visualization systems may be required.

Protein scaffolds: Antibody alternative for cancer diagnosis and therapy

Although antibodies are well developed and widely used in cancer therapy and diagnostic fields, some defects remain, such as poor tissue penetration, long in vivo metabolic retention, potential cytotoxicity, patent limitation, and high production cost. These issues have led scientists to explore and develop novel antibody alternatives. Protein scaffolds are small monomeric proteins with stable tertiary structures and mutable residues, which emerged in the 1990s. By combining robust gene engineering and phage display techniques, libraries with sufficient diversity could be established for target binding scaffold selection. Given the properties of small size, high affinity, and excellent specificity and stability, protein scaffolds have been applied in basic research, and preclinical and clinical fields over the past two decades. To date, more than 20 types of protein scaffolds have been developed, with the most frequently used being affibody, adnectin, ANTICALIN®, DARPins, and knottin. In this review, we focus on the protein scaffold applications in cancer therapy and diagnosis in the last 5 years, and discuss the pros and cons, and strategies of optimization and design.

Although antibodies are well developed and widely used in cancer therapy and diagnostic fields, some defects remain, such as poor tissue penetration, long in vivo metabolic retention, potential cytotoxicity, patent limitation, and high production cost.

Multimodal Contrast Agents for Optoacoustic Brain Imaging in Small Animals

Optoacoustic (photoacoustic) imaging has demonstrated versatile applications in biomedical research, visualizing the disease pathophysiology and monitoring the treatment effect in an animal model, as well as toward applications in the clinical setting. Given the complex disease mechanism, multimodal imaging provides important etiological insights with different molecular, structural, and functional readouts in vivo. Various multimodal optoacoustic molecular imaging approaches have been applied in preclinical brain imaging studies, including optoacoustic/fluorescence imaging, optoacoustic imaging/magnetic resonance imaging (MRI), optoacoustic imaging/MRI/Raman, optoacoustic imaging/positron emission tomography, and optoacoustic/computed tomography. There is a rapid development in molecular imaging contrast agents employing a multimodal imaging strategy for pathological targets involved in brain diseases. Many chemical dyes for optoacoustic imaging have fluorescence properties and have been applied in hybrid optoacoustic/fluorescence imaging. Nanoparticles are widely used as hybrid contrast agents for their capability to incorporate different imaging components, tunable spectrum, and photostability. In this review, we summarize contrast agents including chemical dyes and nanoparticles applied in multimodal optoacoustic brain imaging integrated with other modalities in small animals, and provide outlook for further research.

An overview of the current clinical status of optical imaging in head and neck cancer with a focus on Narrow Band imaging and fluorescence optical imaging

Early and accurate identification of head and neck squamous cell carcinoma (HNSCC) is important to improve treatment outcomes and prognosis. New optical imaging techniques may assist in both the diagnostic process as well as in the operative setting by real-time visualization and delineation of tumor. Narrow Band Imaging (NBI) is an endoscopic technique that uses blue and green light to enhance mucosal and submucosal blood vessels, leading to better detection of (pre)malignant lesions showing aberrant blood vessel patterns. Fluorescence optical imaging makes use of near-infrared fluorescent agents to visualize and delineate HNSCC, resulting in fewer positive surgical margins. Targeted fluorescent agents, such as fluorophores conjugated to antibodies, show the most promising results. The aim of this review is: (1) to provide the clinical head and neck surgeon an overview of the current clinical status of various optical imaging techniques in head and neck cancer; (2) to provide an in-depth review of NBI and fluorescence optical imaging, as these techniques have the highest potential for clinical implementation; and (3) to describe future improvements and developments within the field of these two techniques.

Fluorescence-Guided Visualization of Soft-Tissue Sarcomas by Targeting Vascular Endothelial Growth Factor A: A Phase 1 Single-Center Clinical Trial

Resection of soft-tissue sarcoma (STS) is accompanied by a high rate of tumor-positive surgical margins (14%-34%), which potentially lead to decreased disease-free survival. Vascular endothelial growth factor A is overexpressed in malignant tumors, including STS, and can be targeted with bevacizumab-800CW during fluorescence-guided surgery for real-time tumor detection. In this phase 1 clinical trial, we determined the feasibility, safety, and optimal dose of bevacizumab-800CW for fluorescence-guided surgery in STS for in vivo and ex vivo tumor detection. Methods: Patients with a histopathologic diagnosis of STS were included. In the dose-escalation phase, patients received bevacizumab-800CW intravenously 3 d before surgery (10, 25, and 50 mg; n = 8). In the subsequent dose-expansion phase, 7 additional patients received bevacizumab-800CW at the optimal dose. Fluorescence images were obtained in vivo and ex vivo during all stages of standard care. The optimal dose was determined by calculating in vivo and ex vivo tumor-to-background ratios (TBR) and correlating these results with histopathology. Results: Fifteen patients with STS completed this study. All tumors could be visualized during in vivo and ex vivo imaging. The optimal bevacizumab-800CW dose proved to be 10 mg, with a median in vivo TBR of 2.0 (±0.58) and a median ex vivo TBR of 2.67 (±1.6). All 7 tumor-positive margins could be observed in real time after surgical resection. Conclusion: GS using 10 mg of bevacizumab-800CW is feasible and safe for intraoperative imaging of STS, potentially allowing tumor detection and margin assessment during surgery. An additional follow-up phase 2 study is needed to confirm the diagnostic accuracy.

Candidate Biomarkers for Specific Intraoperative Near-Infrared Imaging of Soft Tissue Sarcomas: A Systematic Review

Simple Summary

Near-infrared imaging of tumors during surgery facilitates the oncologic surgeon to distinguish malignant from healthy tissue. The technique is based on fluorescent tracers binding to tumor biomarkers on malignant cells. Currently, there are no clinically available fluorescent tracers that specifically target soft tissue sarcomas. This review searched the literature to find candidate biomarkers for soft tissue sarcomas, based on clinically used therapeutic antibodies. The search revealed 7 biomarkers: TEM1, VEGFR-1, EGFR, VEGFR-2, IGF-1R, PDGFRα, and CD40. These biomarkers are abundantly present on soft tissue sarcoma tumor cells and are already being targeted with humanized monoclonal antibodies. The conjugation of these antibodies with a fluorescent dye will yield in specific tracers for image-guided surgery of soft tissue sarcomas to improve the success rates of tumor resections.

Abstract

Surgery is the mainstay of treatment for localized soft tissue sarcomas (STS). The curative treatment highly depends on complete tumor resection, as positive margins are associated with local recurrence (LR) and prognosis. However, determining the tumor margin during surgery is challenging. Real-time tumor-specific imaging can facilitate complete resection by visualizing tumor tissue during surgery. Unfortunately, STS specific tracers are presently not clinically available. In this review, STS-associated cell surface-expressed biomarkers, which are currently already clinically targeted with monoclonal antibodies for therapeutic purposes, are evaluated for their use in near-infrared fluorescence (NIRF) imaging of STS. Clinically targeted biomarkers in STS were extracted from clinical trial registers and a PubMed search was performed. Data on biomarker characteristics, sample size, percentage of biomarker-positive STS samples, pattern of biomarker expression, biomarker internalization features, and previous applications of the biomarker in imaging were extracted. The biomarkers were ranked utilizing a previously described scoring system. Eleven cell surface-expressed biomarkers were identified from which 7 were selected as potential biomarkers for NIRF imaging: TEM1, VEGFR-1, EGFR, VEGFR-2, IGF-1R, PDGFRα, and CD40. Promising biomarkers in common and aggressive STS subtypes are TEM1 for myxofibrosarcoma, TEM1, and PDGFRα for undifferentiated soft tissue sarcoma and EGFR for synovial sarcoma.

Dual-agent fluorescent labeling of soft-tissue sarcomas improves the contrast based upon targeting both interstitial and cellular components of the tumor milieu

BACKGROUND

Current practices for fluorescence-guided cancer surgery utilize a single fluorescent agent, but homogeneous distribution throughout the tumor is difficult to achieve. We hypothesize that administering a perfusion and a molecular-targeted agent at their optimal administration-to-imaging time will improve whole-tumor contrast.

EXPERIMENTAL DESIGN

Mice bearing subcutaneous xenograft human synovial sarcomas were administered indocyanine green (ICG) (3 mg/kg) or ABY-029 (48.7 μg/kg)-an epidermal growth factor receptor-targeted Affibody molecule-alone or in combination. Fluorescence contrast and signal distribution were compared between treatment groups. Two commercial fluorescence imaging systems were tested for simultaneous imaging of ICG and ABY-029.

RESULTS

ABY-029 has a moderate positive correlation with viable tumor (ρ = 0.2 ± 0.4), while ICG demonstrated a strong negative correlation (ρ = -0.6 ± 0.1). The contrast-to-variance ratio was highest in the ABY-029 +ICG (2.5 ± 0.8), compared to animals that received ABY-029 (2.3 ± 0.8) or ICG (2.0 ± 0.5) alone. Moreover, the combination of ABY-029 + ICG minimizes the correlation between viable tumor and fluorescence intensity (ρ = -0.1 ± 0.2) indicating the fluorescence signal distribution is more homogeneous throughout the tumor milieu.

CONCLUSION

Dual-agent imaging utilizing a single channel in a commercial fluorescence-guided imaging system tailored for IRDye 800CW is a promising method to increase tumor contrast in a clinical setting.

Quicker, deeper and stronger imaging: A review of tumor-targeted, near-infrared fluorescent dyes for fluorescence guided surgery in the preclinical and clinical stages

Cancer is a public health problem and the main cause of human mortality and morbidity worldwide. Complete removal of tumors and metastatic lymph nodes in surgery is significantly beneficial for the prognosis of patients. Tumor-targeted, near-infrared fluorescent (NIRF) imaging is an emerging field of real-time intraoperative cancer imaging based on tumor-targeted NIRF dyes. Targeted NIRF dyes contain NIRF fluorophores and specific binding ligands such as antibodies, peptides and small molecules. The present article reviews recently updated tumor-targeted NIRF dyes for the molecular imaging of malignant tumors in the preclinical stage and clinical trials. The strengths and challenges of NIRF agents with tumor-targeting ability are also summarized. Smaller ligands, near infrared II dyes, dual-modality dyes and activatable dyes may contribute to quicker, deeper, stronger imaging in the nearest future. In this review, we highlighted tumor-targeted NIRF dyes for fluorescence-guided surgery and their potential clinical translation.

Multidisciplinary treatment of soft tissue sarcomas: An update

Standard treatment for soft tissue sarcoma, based on complete surgical resection with or without adjuvant radiotherapy and chemotherapy, has not substantially changed during the last several decades. Nevertheless, recent advances have contributed to considerable improvement in the management of these patients; for example, new magnetic resonance imaging sequences such as diffusion-weighted imaging and magnetic resonance imaging radiomics can better assess tumor extension and even estimate its grade. Detection of circulating genetic material (liquid biopsy) and next-generation sequencing are powerful techniques for genetic analysis, which will increase our understanding of the underlying molecular mechanisms and may reveal potential therapeutic targets. The role of chemotherapy in non-metastatic disease is still controversial, and there is a need to identify patients who really benefit from this treatment. Novel chemotherapeutic regimens have entered clinical praxis and can change the outcome of patients with metastatic disease. Advances in radiotherapy have helped decrease local adverse effects and sustain good local control of the disease. The following report provides an updated view of the diagnosis, treatment, and future perspectives on the management of patients with soft tissue sarcomas.

Effect of phytase on intestinal phytate breakdown, plasma inositol concentrations, and glucose transporter type 4 abundance in muscle membranes of weanling pigs1

The objective of this present study was to determine the effects of phytase dosing on growth performance, mineral digestibility, phytate breakdown, and the level of glucose transporter type 4 (GLUT4) in muscle plasma membranes of weanling pigs. A total of 160 barrows were used in a randomized completely block design and assigned to 4 treatments for a 7-wk study. Depending on the feeding phase, diets differed in dietary calcium (Ca) and phosphorus (P) levels (positive control [PC]: 8 to 6.8g/kg Ca; 7.3 to 6.3 g/kg P; negative control [NC]: 5.5 to 5.2 g/kg Ca; 5.4 to 4.7 g/kg P). NC diets were supplemented with phytase at 0 (NC); 500 (NC + 500 FTU); or 2,000 FTU/kg (NC + 2,000 FTU) phytase units/kg. Blood was collected after fasting (day 48) or feeding (day 49) for measurement of plasma inositol concentrations. On day 49, 2 pigs per pen were euthanized, and duodenal and ileal digesta samples were collected to determine inositol phosphates (InsP6-2) concentrations. High phytase supplementation increased BW on days 21, 35, and 49 (P < 0.05). Over the entire feeding period, ADG, ADFI, and feed efficiency were increased by NC + 2,000 FTU compared with the other treatments (P < 0.05). Postprandial plasma inositol concentration was increased in NC + 2,000 (P < 0.01), but there was only a tendency (P = 0.06) of a higher fasting plasma inositol concentration in this group. Inositol concentrations in the portal vein plasma (day 49) were not different among treatments. Duodenal digesta InsP5 and InsP6 concentrations were similar in PC and NC, but higher in these 2 treatments (P < 0.05) than those supplemented with phytase. Phytase supplementation decreased InsP6-4, resulting in increased InsP3-2 and myo-inositol concentrations. Similar effects were found in ileal contents. Compared with NC, phytase supplementation resulted in greater cumulative InsP6-2 disappearance (93.6% vs. 72.8% vs. 25.0%, for NC + 2,000 FTU, NC + 500 FTU and NC, respectively, P < 0.01) till the distal ileum. Longissimus dorsi muscle plasma membrane GLUT4 concentration was increased by NC + 2,000 FTU (P < 0.01) compared with NC. In summary, high phytase supplementation increased growth performance of nursery pigs. The higher myo-inositol release from phytate could contribute to the increased expression of GLUT4 in muscle plasma membranes. Further investigation is needed to determine whether this is associated with enhanced cellular glucose uptake and utilization.