Niels J. Harlaar

Intraoperative tumor-specific fluorescence imaging in ovarian cancer by folate receptor-α targeting: first in-human results

The prognosis in advanced-stage ovarian cancer remains poor. Tumor-specific intraoperative fluorescence imaging may improve staging and debulking efforts in cytoreductive surgery and thereby improve prognosis. The overexpression of folate receptor-α (FR-α) in 90–95% of epithelial ovarian cancers prompted the investigation of intraoperative tumor-specific fluorescence imaging in ovarian cancer surgery using an FR-α–targeted fluorescent agent. In patients with ovarian cancer, intraoperative tumor-specific fluorescence imaging with an FR-α–targeted fluorescent agent showcased the potential applications in patients with ovarian cancer for improved intraoperative staging and more radical cytoreductive surgery.

Intraoperative Multispectral Fluorescence Imaging for the Detection of the Sentinel Lymph Node in Cervical Cancer: A Novel Concept

PurposeReal-time intraoperative near-infrared fluorescence (NIRF) imaging is a promising technique for lymphatic mapping and sentinel lymph node (SLN) detection. The purpose of this technical feasibility pilot study was to evaluate the applicability of NIRF imaging with indocyanin green (ICG) for the detection of the SLN in cervical cancer.ProceduresIn ten patients with early stage cervical cancer, a mixture of patent blue and ICG was injected into the cervix uteri during surgery. Real-time color and fluorescence videos and images were acquired using a custom-made multispectral fluorescence camera system.ResultsReal-time fluorescence lymphatic mapping was observed in vivo in six patients; a total of nine SLNs were detected, of which one (11%) contained metastases. Ex vivo fluorescence imaging revealed the remaining fluorescent signal in 11 of 197 non-sentinel LNs (5%), of which one contained metastatic tumor tissue. None of the non-fluorescent LNs contained metastases.ConclusionsWe conclude that lymphatic mapping and detection of the SLN in cervical cancer using intraoperative NIRF imaging is technically feasible. However, the technique needs to be refined for full applicability in cervical cancer in terms of sensitivity and specificity.

Multispectral Optoacoustic Tomography of Matrix Metalloproteinase Activity in Vulnerable Human Carotid Plaques

AimsElevated expression of cathepsins, integrins and matrix metalloproteinases (MMPs) is typically associated with atherosclerotic plaque instability. While fluorescent tagging of such molecules has been amply demonstrated, no imaging method was so far shown capable of resolving these inflammation-associated tags with high fidelity and resolution beyond microscopic depths. This study is aimed at demonstrating a new method with high potential for noninvasive clinical cardiovascular diagnostics of vulnerable plaques using high-resolution deep-tissue multispectral optoacoustic tomography (MSOT) technology.Methods and resultsMMP-sensitive activatable fluorescent probe (MMPSense™ 680) was applied to human carotid plaques from symptomatic patients. Atherosclerotic activity was detected by tuning MSOT wavelengths to activation-dependent absorption changes of the molecules, structurally modified in the presence of enzymes. MSOT analysis simultaneously provided morphology along with heterogeneous MMP activity with better than 200 micron resolution throughout the intact plaque tissue. The results corresponded well with epi-fluorescence images made from thin cryosections. Elevated MMP activity was further confirmed by in situ zymography, accompanied by increased macrophage influx.ConclusionsWe demonstrated, for the first time to our knowledge, the ability of MSOT to provide volumetric images of activatable molecular probe distribution deep within optically diffuse tissues. High-resolution mapping of MMP activity was achieved deep in the vulnerable plaque of intact human carotid specimens. This performance directly relates to pre-clinical screening applications in animal models and to clinical decision potential as it might eventually allow for highly specific visualization and staging of plaque vulnerability thus impacting therapeutic clinical decision making.

Optical innovations in surgery.

In the past decade, there has been a major drive towards clinical translation of optical and, in particular, fluorescence imaging in surgery. In surgical oncology, radical surgery is characterized by the absence of positive resection margins, a critical factor in improving prognosis. Fluorescence imaging provides the surgeon with reliable and real‐time intraoperative feedback to identify surgical targets, including positive tumour margins. It also may enable decisions on the possibility of intraoperative adjuvant treatment, such as brachytherapy, chemotherapy or emerging targeted photodynamic therapy (photoimmunotherapy).

Real-time near infrared fluorescence (NIRF) intra-operative imaging in ovarian cancer using an αvβ3-integrin targeted agent

BACKGROUND In ovarian cancer, optimal cytoreductive surgery is of the utmost importance for long-term survival. The ability to visualize minuscule tumor deposits is important to ensure complete resection of the tumor. The purpose of our study was to estimate the in vivo sensitivity, specificity and diagnostic accuracy of an intra-operative fluorescence imaging system combined with an α(v)β(3)-integrin targeted near-infrared fluorescent probe. METHOD Tumor bearing mice were injected intravenously with a fluorescent probe targeting α(v)β(3) integrins. Fluorescent spots and non-fluorescent tissue were identified and resected. Standard histopathology and fluorescence microscopy were used as gold-standard for tumor detection. RESULTS Fifty-eight samples excised with support of intra-operative image-guided surgery were analyzed. The mean target to background ratio was 2.2 (SD 0.5). The calculated sensitivity of the imaging system was 95%, and the specificity was 88% with a diagnostic accuracy of 96.5%. CONCLUSION Near-infrared image-guided surgery in this model has a high diagnostic accuracy and a fair target to background ratio that supports the development towards clinical translation of α(v)β(3)-integrin targeted imaging.

Multispectral Real-time Fluorescence Imaging for Intraoperative Detection of the Sentinel Lymph Node in Gynecologic Oncology

The prognosis in virtually all solid tumors depends on the presence or absence of lymph node metastases.1-3 Surgical treatment most often combines radical excision of the tumor with a full lymphadenectomy in the drainage area of the tumor. However, removal of lymph nodes is associated with increased morbidity due to infection, wound breakdown and lymphedema.4,5 As an alternative, the sentinel lymph node procedure (SLN) was developed several decades ago to detect the first draining lymph node from the tumor.6 In case of lymphogenic dissemination, the SLN is the first lymph node that is affected (Figure 1). Hence, if the SLN does not contain metastases, downstream lymph nodes will also be free from tumor metastases and need not to be removed. The SLN procedure is part of the treatment for many tumor types, like breast cancer and melanoma, but also for cancer of the vulva and cervix.7 The current standard methodology for SLN-detection is by peritumoral injection of radiocolloid one day prior to surgery, and a colored dye intraoperatively. Disadvantages of the procedure in cervical and vulvar cancer are multiple injections in the genital area, leading to increased psychological distress for the patient, and the use of radioactive colloid. Multispectral fluorescence imaging is an emerging imaging modality that can be applied intraoperatively without the need for injection of radiocolloid. For intraoperative fluorescence imaging, two components are needed: a fluorescent agent and a quantitative optical system for intraoperative imaging. As a fluorophore we have used indocyanine green (ICG). ICG has been used for many decades to assess cardiac function, cerebral perfusion and liver perfusion.8 It is an inert drug with a safe pharmaco-biological profile. When excited at around 750 nm, it emits light in the near-infrared spectrum around 800 nm. A custom-made multispectral fluorescence imaging camera system was used.9. The aim of this video article is to demonstrate the detection of the SLN using intraoperative fluorescence imaging in patients with cervical and vulvar cancer. Fluorescence imaging is used in conjunction with the standard procedure, consisting of radiocolloid and a blue dye. In the future, intraoperative fluorescence imaging might replace the current method and is also easily transferable to other indications like breast cancer and melanoma.

Molecular fluorescence-guided surgery of peritoneal carcinomatosis of colorectal origin: a single-centre feasibility study

BACKGROUND Optimum cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy (HIPEC) is essential for the curative treatment of peritoneal carcinomatosis of colorectal origin. At present, surgeons depend on visual inspection and palpation for tumour detection. Improved detection of tumour tissue using molecular fluorescence-guided surgery could not only help attain a complete cytoreduction of metastatic lesions, but might also prevent overtreatment by avoiding resection of benign lesions. METHODS For this non-randomised, single-centre feasibility study, we enrolled patients with colorectal peritoneal metastases scheduled for cytoreductive surgery and HIPEC. 2 days before surgery, 4·5 mg of the near-infrared fluorescent tracer bevacizumab-IRDye800CW was administered intravenously. The primary objectives were to determine the safety and feasibility of molecular fluorescence-guided surgery using bevacizumab-IRDye800CW. Molecular fluorescence-guided surgery was deemed safe if no allergic or anaphylactic reactions were recorded and no serious adverse events were attributed to bevacizumab-IRDye800CW. The technique was deemed feasible if bevacizumab-IRDye800CW enabled detection of fluorescence signals intraoperatively. Secondary objectives were correlation of fluorescence with histopathology by back-table imaging of the fresh surgical specimen and semi-quantitative ex-vivo analyses of formalin-fixed paraffin embedded (FFPE) tissue on all peritoneal lesions. Additionally, VEGF-α staining and fluorescence microscopy was done. This study is registered with the Netherlands Trial Registry, number NTR4632. FINDINGS Between July 3, 2014, and March 2, 2015, seven patients were enrolled in the study. One patient developed an abdominal sepsis 5 days postoperatively and another died from an asystole 4 days postoperatively, most probably due to a cardiovascular thromboembolic event. However, both serious adverse events were attributed to the surgical cytoreductive surgery and HIPEC procedure. No serious adverse events related to bevacizumab-IRDye800CW occurred in any of the patients. Intraoperatively, fluorescence was seen in all patients. In two patients, additional tumour tissue was detected by molecular fluorescence-guided surgery that was initially missed by the surgeons. During back-table imaging of fresh surgical specimens, a total of 80 areas were imaged, marked, and analysed. All of the 29 non-fluorescent areas were found to contain only benign tissue, whereas tumour tissue was detected in 27 of 51 fluorescent areas (53%). Ex-vivo semi-quantification of 79 FFPE peritoneal lesions showed a tumour-to-normal ratio of 6·92 (SD 2·47). INTERPRETATION Molecular fluorescence-guided surgery using the near-infrared fluorescent tracer bevacizumab-IRDye800CW is safe and feasible. This technique might be of added value for the treatment of patients with colorectal peritoneal metastases through improved patient selection and optimisation of cytoreductive surgery. A subsequent multicentre phase 2 trial is needed to make a definitive assessment of the diagnostic accuracy and the effect on clinical decision making of molecular fluorescence-guided surgery. FUNDING FP-7 Framework Programme BetaCure and SurgVision BV.

Distribution of Matrix Metalloproteinases in Human Atherosclerotic Carotid Plaques and Their Production by Smooth Muscle Cells and Macrophage Subsets

PurposeIn this study, the potential of matrix metalloproteinase (MMP) sense for detection of atherosclerotic plaque instability was explored. Secondly, expression of MMPs by macrophage subtypes and smooth muscle cells (SMCs) was investigated.ProceduresTwenty-three consecutive plaques removed during carotid endarterectomy were incubated in MMPSense™ 680 and imaged with IVIS® Spectrum. mRNA levels of MMPs, macrophage markers, and SMCs were determined in plaque specimens, and in in vitro differentiated M1 and M2 macrophages.ResultsThere was a significant difference between autofluorescence signals and MMPSense signals, both on the intraluminal and extraluminal sides of plaques. MMP-9 and CD68 messenger RNA (mRNA) expression was higher in hot spots, whereas MMP-2 and αSMA expression was higher in cold spots. In vitro M2 macrophages had higher mRNA expression of MMP-1, MMP-9, MMP-12, and TIMP-1 compared to M1 macrophages.ConclusionMMP-9 is most dominantly MMP present in atherosclerotic plaques and is produced by M2 rather than M1 macrophages.

Bioluminescence as Gold Standard for Validation of Optical Imaging Modalities in Peritoneal Carcinomatosis Animal Models

Background: The outcome of cytoreductive surgery in patients with peritoneal carcinomatosis is influenced by incomplete resection as a result of inadequate detection of a tumor, i.e. residual disease. The future perspective of complete resection, made possible by application of intraoperative near-infrared fluorescence imaging (NIRF), led to the development and validation of a bioluminescent colorectal peritoneal carcinomatosis xenograft rat model to act as the gold standard for the evaluation of new optical imaging modalities. Methods: Twenty nude rats were inoculated intraperitoneally with 2 × 106 luciferase-labeled human colorectal tumor cells (HT-29-luc-D6). The peritoneal carcinomatosis index (PCI) was estimated using visual observation (PCI-VO) and VO combined with bioluminescence imaging (PCI-BLI). Subsequently, the BL images were presented, and residual tumor tissue was localized by PCI-BLI scoring and compared with the PCI-VO. Results: BLI revealed additional tumor tissue, confirmed by HE staining, compared to VO alone in 7 out of 8 rats (p < 0.02). Conclusion: The developed model turned out to be suitable. The use of BLI for tumor detection was more sensitive compared to VO alone. In this model, BLI significantly detected residual disease, and therefore, BLI can be denominated as the gold standard for the evaluation of optical imaging modalities like NIRF.

Intraoperative Optical Imaging

During surgery, disease is often detected by visual inspection alone. Inherently, surgical vision is limited however to superficial contrast. In addition, the human eye can recognize anatomical structures, but it is not able to detect molecular-based features. Human vision can be enhanced via the use of targeted and nontargeted fluorescent agents, which can reveal otherwise invisible disease biomarkers.