5-ALA-mediated fluorescence of musculoskeletal tumors in a chick chorio-allantoic membrane model: preclinical in vivo qualification analysis as a fluorescence-guided surgery agent in Orthopedic Oncology

Background Fluorescence-guided surgery (FGS) with 5-aminolevulinic acid (5-ALA) and other contrast agents has shown its efficacy in improving resection margins, local recurrence and survival rates in several medical disciplines. It is the objective of this study to analyze the engraftment rate of musculoskeletal tumor specimens on the chick chorio-allantoic membrane (CAM), the rate of tumor fluorescence (PDD), and the effects of photodynamic therapy (PDT) after exposure of tumors to 5-ALA in an in vivo environment. Methods A total of 486 CAMs were inoculated with macroscopic tumor grafts (n = 26; n = 478 eggs) and primary cell culture suspensions (n = 2; n = 8 eggs) from 26 patients on day 10 of egg development. On day 16, 2 mg/200 µl 5-ALA were topically applied per egg. After 4 h of incubation, Protoporphyrin IX was excited using blue light (420 ± 10 nm). Tumor fluorescence (PDD) was photo-documented. A subgroup of specimens was additionally exposed to red light (635 nm ± 10 nm; PDT). After the termination of the experiment, CAM-grown tumors were histopathologically analyzed. Results Benign and borderline tumors (chondroblastoma, giant cell tumor of bone and atypical chondrogenic tumor) presented with high rates of detectable fluorescence. Comparable results were found for chondrosarcoma, osteosarcoma and Ewing’s sarcoma among bone and dedifferentiated liposarcoma, myxofibrosarcoma and undifferentiated pleomorphic sarcoma among soft tissue sarcomas. Overall, tumor fluorescence was negative for 20.2%, single-positive (+) for 46.9% and double-positive (++) for 32.9% of macroscopic xenografts, and negative in 20% and (+) in 80% of primary cell culture tumors. Macroscopic tumor xenografts (n = 478) were identified as viable in 14.8%, partially viable in 2.9% and partially to completely regressive in 45.2%. All (n = 8) tumors grown from primary cell culture were viable. After PDT, tumor samples were found viable in 5.5%, partially viable in 5.5% and partially to completely regressive in 68%. Egg survival increased with decreasing PDT doses. Conclusions The CAM model proves to be a suitable in vivo model for the investigation of short-term observation questions in musculoskeletal tumors. The findings of this study warrant further investigation of PDT effects on musculoskeletal tumors and a possible incorporation of 5-ALA FGS in clinical Orthopedic Oncology care.

Fluorescence Molecular Targeting of Colon Cancer to Visualize the Invisible

Colorectal cancer (CRC) is a common cause of cancer and cancer-related death. Surgery is the only curative modality. Fluorescence-enhanced visualization of CRC with targeted fluorescent probes that can delineate boundaries and target tumor-specific biomarkers can increase rates of curative resection. Approaches to enhancing visualization of the tumor-to-normal tissue interface are active areas of investigation. Nonspecific dyes are the most-used approach, but tumor-specific targeting agents are progressing in clinical trials. The present narrative review describes the principles of fluorescence targeting of CRC for diagnosis and fluorescence-guided surgery with molecular biomarkers for preclinical or clinical evaluation.

Activatable molecular probes for fluorescence-guided surgery, endoscopy and tissue biopsy

We highlight the development of activatable molecular probes that trigger the optical signals toward biomarkers, allowing real-time, dynamic visualization of lesions and margins for guided-surgery, endoscopy and tissue biopsy with molecular precision.

Qualitative head-to-head comparison of headlamp and microscope for visualizing 5-ALA fluorescence during resection of glioblastoma

Fluorescence-guided surgery (FGS) for high-grade gliomas using 5-aminolevulinic acid has become a new standard of care for neurosurgeons in several countries. In this video the authors present the case of a man with glioblastoma who underwent FGS in which similar images of the operative field were acquired alternating between the microscope and a new commercially available headlight, facilitating the comparison of visualization quality between the two devices. The authors also review some of the principles of fluorescence-guidance surgery that may explain the improved brightness and contrast that they observed when using the headlamp versus the microscope. The video can be found here: https://stream.cadmore.media/r10.3171/2021.10.FOCVID21181

Intraoperative Near-Infrared Fluorescence Guided Surgery Using Indocyanine Green (ICG) for the Resection of Sarcomas May Reduce the Positive Margin Rate: An Extended Case Series

Background: Sarcomas are rare, aggressive cancers which can occur in any region of the body. Surgery is usually the cornerstone of curative treatment, with negative surgical margins associated with decreased local recurrence and improved overall survival. Indocyanine green (ICG) is a fluorescent dye which accumulates in sarcoma tissue and can be imaged intraoperatively using handheld near-infrared (NIR) cameras, theoretically helping guide the surgeon’s resection margins. Methods: Patients operated on between 20 February 2019 and 20 October 2021 for intermediate to high grade sarcomas at our centres received either conventional surgery, or were administered ICG pre-operatively followed by intra-operative NIR fluorescence guidance during the procedure. Differences between the unexpected positive margin rates were compared. Results: 115 suitable patients were identified, of which 39 received ICG + NIR fluorescence guided surgery, and 76 received conventional surgery. Of the patients given ICG, 37/39 tumours fluoresced, and surgeons felt the procedure was guided by the intra-operative images in 11 cases. Patients receiving ICG had a lower unexpected positive margin rate (5.1% vs. 25.0%, p = 0.01). Conclusions: The use of NIR fluorescence cameras in combination with ICG may reduce the unexpected positive margin rate for high grade sarcomas. A prospective, multi-centre randomised control trial is now needed to validate these results.

Near-Infrared Imaging With Indocyanine Green for the Treatment of Endometriosis: Results From the Gre-Endo Trial

IntroductionA current challenge for endometriosis surgery is to correctly identify the localizations of disease, especially when small or hidden (occult endometriosis), and to exactly define their real extension. The use of near-infrared radiation imaging (NIR) after injection of indocyanine green (ICG) represents one of the most encouraging method. The aim of this study is to assess the diagnostic value of NIR-ICG imaging in the surgical treatment of endometriosis compared with the standard of treatment.Material and MethodsThe Gre-Endo trial is a prospective, single-arm study (NCT03332004). After exploring the operatory field using the white light (WL) mode, patients were injected with ICG and then observed in NIR mode. All suspected areas were classified and chronicled according to lesions visualized only in WL, NIR-ICG, or in the combination of both. Lesion not visualized in WL was considered as suspect occult lesion (s-OcL). In addition, a random control biopsy from an apparent negative peritoneum visualized in WL and NIR-ICG imaging was taken for all patients (control cases). All lesions removed were considered “suspect endometriosis” until pathology.ResultsFifty-one patients were enrolled between January 2016 and October 2019. A total of 240 suspected lesions have been identified with both methods (WL + NIR-ICG). Two hundred and seven (86.2%) lesions out of the overall 240 were visualized with WL imaging, and 200 were confirmed to be pathologic (true positive for WL). The remaining 33/240 (13.75%) (false negative for WL) lesions were identified only with NIR-ICG imaging and collected as s-OcL. All 33 s-OcLs removed were confirmed to be pathologic (c-OcL = 100%). NIR-ICG vision showed PPV of 98.5%, NPV of 87.1%, Se of 87%, and Sp of 98.5%, confirming that this kind of imaging is an excellent diagnostic and screening test (p = 0.001 and p = 0.835, according to McNemar’s and Cohen’s kappa tests, respectively).ConclusionsThe use of NIR-ICG vision alone and combined with WL showed good results in intraoperative detection rate and fluorescence-guided surgery of endometriosis. Furthermore, NIR-ICG allowed surgeons to remove occult lesions that otherwise would remain, leading to possible greater postoperative pain and a higher risk of persistence and relapse.

BIOM-45. CHARACTERIZATION OF EVs RELEASED FROM 5-ALA DOSED GLIAL AND EXTRA-AXIAL TUMORS

INTRODUCTION The administration of 5-Aminolevunlinic acid (5-ALA) in the context of fluorescence-guided surgery is contingent on the highly selective accumulation of PpIX in tumor cells. PpIX is a precursor in the heme pathway that naturally exhibits fluorescent and phototoxic properties upon excitation. We have previously reported evidence of PpIX fluorescence in tumor-specific extracellular vesicles (EVs). Here, we explore the implications of exogenous 5-ALA on cellular function, EV characteristics, and gene expression. METHODS We have characterized a range of glioblastoma, meningioma, and healthy cell lines (Gli36 EGFRvIII, Gli36 EGFR WT, U87, CH-157, IOMM-Lee, and HBMVEC). At equal confluency, cells were dosed with 0.8 mM 5-ALA or mock dosed. Media was collected and processed to eliminate debris after 24 hours. Analysis of cells and EVs was conducted using Amnis ImageStream (IFC) and Nanoparticle Tracking Analysis. EV subpopulations were analyzed with IFC following antibody staining. RNA was extracted using Qiagen exoRNeasy and RNeasy. Libraries were prepared via Qiagen UPX 3’ Transcriptome kit and sequenced using Illumina MiSeq. Data analysis was carried out via GeneGlobe, CLC workbench, and MATLAB. RESULTS Following 5-ALA dosing, all tumor cells and their derived EVs exhibit significant levels of fluorescence. Analysis of EV subpopulations demonstrated a general decrease in tetraspanin-positive EVs following 5-ALA dosing. At 24 hours, Gli36 cell lines exhibited increased EV release post 5-ALA whereas U87 and meningioma lines resulted in a decreased EV release rate. This clustering is also reflected in EV size distributions and in cellular and EV differential gene expression analysis. Gene ontology analysis of common genes from mock and dosed EVs demonstrated high counts of genes controlling biological regulation as well as cellular and metabolic processes. CONCLUSION Collection and characterization of cancer specific EVs may be advantageous to liquid biopsy development.

BIOM-12. DEVELOPMENT OF 5-ALA BASED LIQUID BIOPSY FOR THE NON-INVASIVE DIAGNOSIS OF GLIOBLASTOMA

INTRODUCTION Tumor specificity of 5-aminolevulinic acid (5-ALA) induced protoporphyrin IX (PpIX) fluorescence is widely applied for fluorescence-guided surgery (FGS) in gliomas. We recently showed the feasibility of detecting tumour-specific fluorescent PpIX extracellular vesicles (EVs) derived from the plasma of glioblastoma (GBM) patients undergoing 5-ALA based fluorescence-guided surgery. Here, we further develop methods to characterize, sort and study fluorescent PpIX EVs in plasma of patients with glioma. METHODS We used imaging flow cytometry and Astrios EQ nanoFACS to characterize and sort PpIX EVs, respectively. Downstream RNA analysis utilized transcriptome sequencing analysis and droplet digital PCR (EGFRvIII mRNA). RESULTS All GBM cell lines (Gli36vIII, U87, Gli36 WT) dosed with 5-ALA demonstrated PpIX fluorescence, and released PpIX positive EVs. There was a high correlation between fluorescence in cells and the number of PpIX EVs released (r2=0.9). We sorted 100,000 PpIX EVs from Gli36vIII cells dosed with 5-ALA and detected 65 copies and 24 copies of mutant EGFRvIII mRNA and wildtype EGFR mRNA per 100,000 EVs, respectively. RNAseq analysis of the sorted PpIX EVs showed expression patterns reflective of parent cells. Furthermore, 100,000 sorted PpIX EVs from the plasma of a patient with EGFRvIII glioma yielded 22 copies of EGFRvIII mRNA while < 5 copies were detected in 1ml of plasma and healthy control plasma, demonstrating the tumor-specific nature of PpIX EVs. Finally, we performed transcriptome analysis on 250,000 PpIX EVs each from 8 patients undergoing 5-ALA based FGS. We identified several mRNAs including Gli3, STAG2, ELF3, PHLPP1 which play an important role in cancer. CONCLUSION The ability to sort and characterize tumor specific PpIX EVs following 5-ALA administration opens new avenues for liquid biopsy-based glioma diagnosis.

FLGS-04. Fluorescence lifetime imaging (FLIm) is a dye-free, high sensitivity approach for fluorescence guided surgery in high-grade and low-grade gliomas

INTRODUCTION Fluorescence-guided surgery can improve tumor identification and extent of surgical resection. 5-ALA is the standard for GBM, but is limited by lack of quantitative fluorescence, a need to work in the dark, and a lack of sensitivity for low grade tumors. We have developed a novel instrument for dye-free tissue autofluorescence lifetime imaging (FLIm) to identify glioma tissue during resection. This approach utilizes time-resolved autofluorescence measurements in narrow-band channels to assess markers of tissue metabolism. Compared to intensity-based imaging of exogenous fluorophores, FLIm has greater sensitivity without dependence on background lighting. The advantages of FLIm include quantitative tissue analysis, the ability to work under full light conditions, sensitivity for high and low grade gliomas, and the potential ability to identify IDH mutational status. In this study, we validated the use of FLIm for identification of glioma tissue at tumor resection margins. METHODS FLIm was used to image tissue margins during glioma resections and compared to microbiopsies from imaged regions to correlate fluorescence with histopathology. RESULTS FLIm was applied intraoperatively to 11 GBM and 5 LGG patients (7 imaged biopsies per patient). In GBM, tumor infiltration of cortex was associated with significantly decreased fluorescence lifetime (FL) in channels 2 (470/28nm;p<0.05) and 3 (542/50nm;p<0.002). In subcortical margins, FL was inversely proportional to the density of tumor in channels 2,3 (p<0.05). When IDH wild-type GBMs were compared to IDH1-mutant tumors, FL was noted to be significantly longer in channel 1 (390/40nm;p<0.05), and trended towards longer FL in channel 2, shorter FL in channel 3. In LGG, FL was significantly correlated with tumor density in channel 2 (p<0.01). CONCLUSIONS FLIm is a dye-free, quantitative alternative to 5-ALA for fluorescence guided glioma resections with sensitivity to high and low-grade tumors, and the ability to predict IDH mutations in GBM. Further validation studies are on-going.

Applications of fluorescence-guided surgery across multiple tumor types using a near-infrared labeled EGFR antibody

Background As receptor-ligand based strategies emerge for surgical imaging, the relative importance of receptor expression in different tumor types is unknown. Near-infrared (NIR) labeled epidermal growth factor receptor (EGFR) antibody, panitumumab-IRDye800, was evaluated across three cancers to demonstrate its clinical utilities and a holistic analysis framework. Methods Thirty-one patients diagnosed with high-grade glioma (HGG, n=5, NCT03510208), head and neck squamous cell carcinoma (HNSCC, n=23, NCT02415881) or lung adenocarcinoma (LAC, n=3, NCT03582124) received systemic administration of 50 mg panitumumab-IRDye800 days prior to surgery. Intraoperative NIR laparoscopic or open-field images of the surgical field were acquired and tissue mimicking phantoms were constructed to identify optimal imaging conditions. Margin distance was correlated to fluorescence on resected specimen surface. Panitumumab-IRDye800 distribution was registered to histology in fixed tissue sections. Immunohistochemistry characterized EGFR expression. Results Intraoperative NIR imaging enhanced tumor contrast against surrounding healthy tissue by 5.2-fold, 3.4-fold and 1.4-fold in HGG, HNSCC and LAC, respectively. Imaging quality was optimal at the lowest gain possible under ambient light. Ex vivo NIR fluorescence identified 78-97% of at-risk resection margins, with 72-92% sensitivity and 67-96% specificity for tumor in fixed tissue sections. Intratumoral panitumumab-IRDye800 concentration correlated with total tumoral EGFR expression (HGG > HNSCC > LAC) and delivery barrier. Cellular EGFR expression (80%) and tumor cell density (3000 cells/mm2) was highest in HGG. Conclusions In multiple tumor types, EGFR-targeting in fluorescence-guided surgery translated to enhanced macroscopic tumor contrast and successful margin assessment despite disparate tumor cell density and heterogeneous delivery of pantimumab-IRDye800.