Merlijn Hutteman

The clinical use of indocyanine green as a near-infrared fluorescent contrast agent for image-guided oncologic surgery

Optical imaging using near‐infrared (NIR) fluorescence provides new prospects for general and oncologic surgery. ICG is currently utilised in NIR fluorescence cancer‐related surgery for three indications: sentinel lymph node (SLN) mapping, intraoperative identification of solid tumours, and angiography during reconstructive surgery. Therefore, understanding its advantages and limitations is of significant importance. Although non‐targeted and non‐conjugatable, ICG appears to be laying the foundation for more widespread use of NIR fluorescence‐guided surgery. J. Surg. Oncol. 2011; 104:323–332.

Image-guided cancer surgery using near-infrared fluorescence

Paradigm shifts in surgery arise when surgeons are empowered to perform surgery faster, better and less expensively than current standards. Optical imaging that exploits invisible near-infrared (NIR) fluorescent light (700–900 nm) has the potential to improve cancer surgery outcomes, minimize the time patients are under anaesthesia and lower health-care costs largely by way of its improved contrast and depth of tissue penetration relative to visible light. Accordingly, the past few years have witnessed an explosion of proof-of-concept clinical trials in the field. In this Review, we introduce the concept of NIR fluorescence imaging for cancer surgery, examine the clinical trial literature to date and outline the key issues pertaining to imaging system and contrast agent optimization. Although NIR seems to be superior to many traditional imaging techniques, its incorporation into routine care of patients with cancer depends on rigorous clinical trials and validation studies.

Optical Image-guided Surgery—Where Do We Stand?

In cancer surgery, intra-operative assessment of the tumor-free margin, which is critical for the prognosis of the patient, relies on the visual appearance and palpation of the tumor. Optical imaging techniques provide real-time visualization of the tumor, warranting intra-operative image-guided surgery. Within this field, imaging in the near-infrared light spectrum offers two essential advantages: increased tissue penetration of light and an increased signal-to-background-ratio of contrast agents. In this article, we review the various techniques, contrast agents, and camera systems that are currently used for image-guided surgery. Furthermore, we provide an overview of the wide range of molecular contrast agents targeting specific hallmarks of cancer and we describe perspectives on its future use in cancer surgery.

Near-infrared fluorescence-guided resection of colorectal liver metastases

The fundamental principle of oncologic surgery is the complete resection of malignant cells. However, small tumors are often difficult to find during surgery using conventional techniques. The objectives of this study were to determine if optical imaging, using a contrast agent already approved for other indications, could improve hepatic metastasectomy with curative intent, to optimize dose and timing, and to determine the mechanism of contrast agent accumulation.

The FLARE intraoperative near-infrared fluorescence imaging system: a first-in-human clinical trial in perforator flap breast reconstruction.

Background: The ability to determine flap perfusion in reconstructive surgery is still primarily based on clinical examination. In this study, the authors demonstrate the use of an intraoperative, near-infrared fluorescence imaging system for evaluation of perforator location and flap perfusion. Methods: Indocyanine green was injected intravenously in six breast cancer patients undergoing a deep inferior epigastric perforator flap breast reconstruction after mastectomy. Three dose levels of indocyanine green were assessed using the fluorescence-assisted resection and exploration (FLARE) imaging system. This system uses light-emitting diodes for fluorescence excitation, which is different from current commercially available systems. In this pilot study, the operating surgeons were blinded to the imaging results. Results: Use of the FLARE system was successful in all six study subjects, with no complications or sequelae. Among the three dose levels, 4 mg per injection resulted in the highest observed contrast-to-background ratio, signal-to-background ratio, and signal-to-noise ratio. However, because of small sample size, the authors did not have sufficient power to detect statistical significance for these pairwise comparisons at the multiple-comparison adjusted type I error of 0.017. Six milligrams per injection provided a similar contrast-to-background ratio but also a higher residual background signal. Conclusion: Based on this pilot study, the authors conclude that near-infrared assessment of perforator flap breast reconstruction is feasible with a light-emitting diode–based system, and that a dose of 4 mg of indocyanine green per injection yields the best observed contrast-to-background ratio compared with a dose of 2 or 6 mg for assessment of flap perfusion.

Near-infrared fluorescence sentinel lymph node mapping of the oral cavity in head and neck cancer patients

OBJECTIVES Elective neck dissection is frequently performed during surgery in head and neck cancer patients. The sentinel lymph node (SLN) procedure can prevent the morbidity of a neck dissection and improve lymph node staging by fine pathology. Near-infrared (NIR) fluorescence imaging is a promising technique to identify the sentinel lymph node (SLN) intraoperatively. This feasibility study explored the use of indocyanine green adsorbed to human serum albumin (ICG:HSA) for SLN mapping in head and neck cancer patients. MATERIALS AND METHODS A total of 10 consecutive patients with oral cavity or oropharyngeal cancer and a clinical N0 neck were included. After exposure of the neck, 1.6 mL of ICG:HSA (500 μM) was injected at four quadrants around the tumor. During the neck dissection, levels I-IV were measured for fluorescence using the Mini-FLARE imaging system. RESULTS In all 10 patients, NIR fluorescence imaging enabled visualization of one or more SLNs. A total of 17 SLNs were identified. The mean contrast between the fluorescent signal of the lymph nodes and of the surrounding tissue was 8.7±6.4. In 3 patients, of which 1 was false-negative, lymph node metastases were found. After administration of ICG:HSA, the average number of fluorescent lymph nodes significantly increased over time (P<0.001). CONCLUSION This study demonstrated feasibility to detect draining lymph nodes in head and neck cancer patients using NIR fluorescence imaging. However, the fluorescent tracer quickly migrated beyond the SLN to higher tier nodes.

Intraoperative near-infrared fluorescence imaging in perforator flap reconstruction: current research and early clinical experience.

Despite recent advances in perforator flap reconstruction, there can be significant variability in vessel size and location. Although preoperative evaluation may provide valuable information, real-time intraoperative methods have the potential to provide the greatest benefit. Our laboratory has developed the Fluorescence-Assisted Resection and Exploration (FLARE) near-infrared (NIR) fluorescence imaging system for intraoperative visualization of details of the underlying vasculature. The FLARE system uses indocyanine green, a safe and reliable NIR fluorophore already FDA-approved for other indications. The system has been optimized in large-animal models for the identification of perforator size, location, and perfusion and has also been translated to the clinic for use during breast reconstruction after mastectomy. In this article, we review our preclinical and clinical data, as well as literature describing the use of similar NIR fluorescence imaging systems in plastic and reconstructive surgery.

Optimization of near-infrared fluorescent sentinel lymph node mapping in cervical cancer patients.

Objective: In early cervical cancer, a total pelvic lymphadenectomy is the standard of care, even though most patients have negative nodes and thus undergo lymphadenectomy unnecessarily. Although the value of sentinel lymph node (SLN) mapping in early-stage cervical cancer has not yet been established, near-infrared (NIR) fluorescence imaging is a promising technique to perform this procedure. Near-infrared fluorescence imaging is based on invisible NIR light and can provide high sensitivity, high-resolution, and real-time image guidance during surgery. Methods: Clinical trial subjects were 9 consecutive cervical cancer patients undergoing total pelvic lymphadenectomy. Before surgery, 1.6 mL of indocyanine green adsorbed to human serum albumin (ICG:HSA) was injected transvaginally and submucosally in 4 quadrants around the tumor. Patients were allocated to 500-, 750-, or 1000-&mgr;M ICG:HSA concentration groups. The Mini-FLARE imaging system was used for NIR fluorescence detection and quantitation. Results: Sentinel lymph nodes were identified in all 9 patients. An average of 3.4 ± 1.2 SLNs was identified per patient. No differences in signal to background of the SLNs between the 500-, 750-, and 1000-&mgr;M dose groups were found (P = 0.73). In 2 patients, tumor-positive lymph nodes were found. In both patients, tumor-positive lymph nodes confirmed by pathology were also NIR fluorescent. Conclusions: This study demonstrated preliminary feasibility to successfully detect SLNs in cervical cancer patients using ICG:HSA and the Mini-FLARE imaging system. When considering safety, cost-effectiveness, and pharmacy preferences, an ICG:HSA concentration of 500 &mgr;M was optimal for SLN mapping in cervical cancer patients.

Dose optimization for near-infrared fluorescence sentinel lymph node mapping in patients with melanoma.

Background  Regional lymph node involvement is the most important prognostic factor in cutaneous melanoma. As only 20% of patients with melanoma have occult nodal disease and would benefit from a regional lymphadenectomy, the sentinel lymph node (SLN) biopsy was introduced. Near‐infrared (NIR) fluorescence has been hypothesized to improve SLN mapping.

Image-guided hepatopancreatobiliary surgery using near-infrared fluorescent light

BackgroundImproved imaging methods and surgical techniques have created a new era in hepatopancreatobiliary (HPB) surgery. Despite these developments, visual inspection, palpation, and intraoperative ultrasound remain the most utilized tools during surgery today. This is problematic, though, especially in laparoscopic HPB surgery, where palpation is not possible. Optical imaging using near-infrared (NIR) fluorescence can be used for the real-time assessment of both anatomy (e.g., sensitive detection and demarcation of tumours and vital structures) and function (e.g., assessment of luminal flow and tissue perfusion) during both open and minimally invasive surgeries.MethodsThis article reviews the published literature related to preclinical development and clinical applications of NIR fluorescence imaging during HPB surgery.ResultsNIR fluorescence imaging combines the use of otherwise invisible NIR fluorescent contrast agents and specially designed camera systems, which are capable of detecting these contrast agents during surgery. Unlike visible light, NIR fluorescent light can penetrate several millimetres through blood and living tissue, thus providing improved detectability. Applications of this technique during HPB surgery include tumour imaging in liver and pancreas, and real-time imaging of the biliary tree.ConclusionsNIR fluorescence imaging is a promising new technique that may someday improve surgical accuracy and lower complications.