Intraoperative Sentinel Lymph Node Mapping Using a New Sterilizable Magnetometer in Patients with Nonsmall Cell Lung Cancer

Molecular image-guided surgery in gynaecological cancer: where do we stand?

PURPOSE

The aim of this review is to give an overview of the current status of molecular image-guided surgery in gynaecological malignancies, from both clinical and technological points of view.

METHODS

A narrative approach was taken to describe the relevant literature, focusing on clinical applications of molecular image-guided surgery in gynaecology, preoperative imaging as surgical roadmap, and intraoperative devices.

RESULTS

The most common clinical application in gynaecology is sentinel node biopsy (SNB). Other promising approaches are receptor-target modalities and occult lesion localisation. Preoperative SPECT/CT and PET/CT permit a roadmap for adequate surgical planning. Intraoperative detection modalities span from 1D probes to 2D portable cameras and 3D freehand imaging.

CONCLUSION

After successful application of radio-guided SNB and SPECT, innovation is leaning towards hybrid modalities, such as hybrid tracer and fusion of imaging approaches including SPECT/CT and PET/CT. Robotic surgery, as well as augmented reality and virtual reality techniques, is leading to application of these innovative technologies to the clinical setting, guiding surgeons towards a precise, personalised, and minimally invasive approach.

Sentinel lymph node biopsy for lung cancer

Sentinel lymph node biopsy is a technique to identify the first lymph node (or nodes) draining a tumor. The underlying principle is that as the first site of cancer spread, evaluation of the sentinel node will be most predictive for wider nodal involvement. The introduction of sentinel node biopsy revolutionized the surgical management of cutaneous melanoma and breast cancer, becoming a key component in the management of such patients. For over 20 years, thoracic surgeons have similarly worked to apply this technique to lung cancer but have thus far not had the same impact on lung surgery. In this review, we will summarize the ongoing discussions on the role of sentinel node biopsy in lung cancer, the methods for identifying the sentinel node, and the techniques for evaluating the sentinel node specimen. We will also highlight some of the pressing questions investigators should consider when designing a trial for sentinel node mapping. This will clarify the current status of sentinel node biopsy in lung cancer and thus highlight important future directions for research.

Hybrid 99mTc-magnetite tracer for dual modality sentinel lymph node mapping

Accuracy of sentinel lymph node identification using radioactive tracers in non-superficial cancers can be limited by radiation shine through and low spatial resolution of detection systems such as intraoperative gamma probes. By utilising a dual radioactive/magnetic tracer, sensitive lymphoscintigraphy can be paired with high spatial resolution intraoperative magnetometer probes to improve the accuracy of sentinel node detection in cancers with complex multidirectional lymphatic drainage. Dextran-coated magnetite nanoparticles (33 nm mean hydrodynamic diameter) were labelled with ^99mTc and applied as a lymphotropic tracer in small and large animal models. The dual tracer could be radiolabelled with 98 ± 2% efficiency after 10 min of incubation at room temperature. Biodistribution studies of the tracer were conducted in normal rats (subdermal and intravenous tail delivery, n = 3) and swine (subdermal hind limb delivery, n = 5). In rats the dual tracer migrated through four tiers of lymph node, 20 min after subdermal injection. Results from intravenous biodistribution test for radiocolloids demonstrated no aggregation in vivo, however indicated the presence of some lower-molecular weight radioactive impurities (^99mTc-dextran). In swine, the dual tracer could be effectively used to map lymphatic drainage from hind hoof to popliteal and inguinal basins using intraoperative gamma and magnetometer probes. Of the eight primary nodes excised, eight were positively identified by gamma probe and seven by magnetometer probe. The high-purity dual tracer shows early promise for sentinel node identification in complex lymphatic environments by combining sensitive preoperative lymphoscintigraphy with a high-resolution intraoperative magnetometer probe.

Biopsy of the sentinel node in lung cancer

INTRODUCTION AND OBJECTIVE

Mediastinal lymph node involvement can be understaged in cases of lung cancer (up to 20% in stage i). Sentinel node detection is a standard technique recommended in breast cancer and melanoma action guidelines, and could also be useful in cases of lung cancer.

MATERIAL AND METHODS

Considering the detection of the sentinel node in non-small cell lung cancer (NSCLC) as feasible, a prospective cohort study was carried out on 48 patients with resectable NSCLC, using the intraoperative injection of colloid sulphate technetium-99.

RESULTS

The radioisotope migrated in all cases. The procedure's sensitivity was 88.24%, its accuracy was 95.83%, its negative predictive value was 93.94% and the false negative rate was 11.76%. No complications were associated with this technique.

CONCLUSIONS

The detection of a sentinel node in NSCLC with the intraoperative injection of the isotope is feasible and safe, and allows for detection and sensitivity rates comparable to those of other tumour types.

A comprehensive literatures update of clinical researches of superparamagnetic resonance iron oxide nanoparticles for magnetic resonance imaging

This paper aims to update the clinical researches using superparamagnetic iron oxide (SPIO) nanoparticles as magnetic resonance imaging (MRI) contrast agent published during the past five years. PubMed database was used for literature search, and the search terms were (SPIO OR superparamagnetic iron oxide OR Resovist OR Ferumoxytol OR Ferumoxtran-10) AND (MRI OR magnetic resonance imaging). The literature search results show clinical research on SPIO remains robust, particularly fuelled by the approval of ferumoxytol for intravenously administration. SPIOs have been tested on MR angiography, sentinel lymph node detection, lymph node metastasis evaluation; inflammation evaluation; blood volume measurement; as well as liver imaging. Two experimental SPIOs with unique potentials are also discussed in this review. A curcumin-conjugated SPIO can penetrate brain blood barrier (BBB) and bind to amyloid plaques in Alzheime's disease transgenic mice brain, and thereafter detectable by MRI. Another SPIO was fabricated with a core of Fe3O4 nanoparticle and a shell coating of concentrated hydrophilic polymer brushes and are almost not taken by peripheral macrophages as well as by mononuclear phagocytes and reticuloendothelial system (RES) due to the suppression of non-specific protein binding caused by their stealthy ''brush-afforded'' structure. This SPIO may offer potentials for the applications such as drug targeting and tissue or organ imaging other than liver and lymph nodes.

In vivo biodistribution studies and ex vivo lymph node imaging using heavy metal-free quantum dots

Quantum dots (QDs) are attractive photoluminescence probes for biomedical imaging due to their unique photophysical properties. However, the potential toxicity of QDs has remained a major obstacle to their clinical use because they commonly incorporate the toxic heavy metal cadmium within the core of the QDs. In this work, we have evaluated a novel type of heavy metal-free/cadmium-free and biocompatible QD nanoparticles (bio CFQD(®) nanoparticles) with a good photoluminescence quantum yield. Sentinel lymph node mapping is an increasingly important treatment option in the management of breast cancer. We have demonstrated their potential for lymph node mapping by ex vivo imaging of regional lymph nodes after subcutaneous injection in the paw of rats. Using photoluminescence imaging and chemical extraction measurements based on elemental analysis by inductively coupled plasma mass spectroscopy, the quantum dots are shown to accumulate quickly and selectively in the axillary and thoracic regional lymph nodes. In addition, lifetime imaging microscopy of the QD photoluminescence indicates minimal perturbation to their photoluminescence properties in biological systems.

Development of a New Magnetometer for Sentinel Lymph Node Mapping Designed for Video-Assisted Thoracic Surgery in Non-Small Cell Lung Cancer

BACKGROUND

We previously developed a method for sentinel lymph node (SLN) mapping in non-small cell lung cancer (NSCLC), based on the magnetic force produced by a magnetite tracer already approved for use as a contrast material for magnetic resonance imaging. However, it is difficult to use that technique with video-assisted thoracic surgery (VATS) because the sensing element of the magnetometer is large and thick. The purpose of the present study was to develop a smaller, thinner VATS-compatible magnetometer.

METHODS

The tracer employed was Ferucarbotran, a colloidal solution of superparamagnetic iron oxide coated with carbodextran. Fifteen patients with clinical stage I NSCLC were enrolled, and each received 1.6 mL of Ferucarbotran, injected intraoperatively at 5 points around the tumor. The magnetic force within the sampling lymph nodes was measured using the new VATS-compatible magnetometer.

RESULTS

SLNs were detected in 11 (73.3%) of the 15 patients using the VATS-compatible magnetometer. The average number of SLNs identified per patient was 1.8 (range 0-4). No complications related to the SLN detection method were observed.

CONCLUSIONS

The new VATS-compatible magnetometer appears to have substantial advantages over techniques using a radioisotope and our earlier magnetometer, as it can be inserted through the small VATS port site.

Novel techniques for sentinel lymph node biopsy in breast cancer: a systematic review

The existing standard for axillary lymph node staging in breast cancer patients with a clinically and radiologically normal axilla is sentinel lymph node biopsy with a radioisotope and blue dye (dual technique). The dependence on radioisotopes means that uptake of the procedure is limited to only about 60% of eligible patients in developed countries and is negligible elsewhere. We did a systematic review to assess three techniques for sentinel lymph node biopsy that are not radioisotope dependent or that refine the existing method: indocyanine green fluorescence, contrast-enhanced ultrasound using microbubbles, and superparamagnetic iron oxide nanoparticles. Our systematic review suggested that these new methods for sentinel lymph node biopsy have clinical potential but give high levels of false-negative results. We could not identify any technique that challenged the existing standard procedure. Further assessment of these techniques against the standard dual technique in randomised trials is needed.

Clinical relevance of novel imaging technologies for sentinel lymph node identification and staging

The sentinel lymph node (SLN) concept has become a standard of care for patients with breast cancer and melanoma, yet its clinical application to other cancer types has been somewhat limited. This is mainly due to the reduced accuracy of conventional SLN mapping techniques (using blue dye and/or radiocolloids as lymphatic tracers) in cancer types where lymphatic drainage is more complex, and SLNs are within close proximity to other nodes or the tumour site. In recent years, many novel techniques for SLN mapping have been developed including fluorescence, x-ray, and magnetic resonant detection. Whilst each technique has its own advantages/disadvantages, the role of targeted contrast agents (for enhanced retention in the SLN, or for immunostaging) is increasing, and may represent the new standard for mapping the SLN in many solid organ tumours. This review article discusses current limitations of conventional techniques, limiting factors of nanoparticulate based contrast agents, and efforts to circumvent these limitations with modern tracer architecture.

The role of magnetic nanoparticles in the localization and treatment of breast cancer

The role of magnetic nanoparticles (MNPs) in medical applications is rapidly developing. Advances in nanotechnology are bringing us closer to the development of dual and multifunctional nanoparticles that are challenging the traditional distinction between diagnostic and treatment agents. The current use of MNPs in breast cancer falls into four main groups: (1) imaging of primary and metastatic disease, (2) sentinel lymph node biopsy (SLNB), (3) drug delivery systems, and (4) magnetic hyperthermia. The current evidence for the use of MNPs in these fields is mounting, and potential cutting-edge clinical applications, particularly with relevance to the fields of breast oncological surgery, are emerging.

Intraoperative nodal staging: role of sentinel node technology

In cases of superficial malignancies such as melanoma or breast cancer, intraoperative lymph node mapping with a sentinel lymph node (SLN) biopsy is an effective and minimally invasive alternative to inguinal or axillary lymph node dissection for early-stage tumors. For primary lung cancer, although much effort has been made to investigate a variety of tracers, such as dyes, radioisotopes, magnetite, and iopamidol, for discerning SLNs, an appropriate agent that produces high identification and accuracy rates has yet to be developed. Further studies are needed to find an ideal tracer for practical use in patients with non-small cell lung cancer.

Quantitative analysis of superparamagnetic contrast agent in sentinel lymph nodes using ex vivo vibrating sample magnetometry

As the first step in developing a new clinical technique for the magnetic detection of colorectal sentinel lymph nodes (SLNs), a method is developed to measure the magnetic content in intact, formalin fixated lymph nodes using a vibrating sample magnetometer (VSM). A suspension of superparamagnetic nanoparticles is injected ex vivo around the tumor in the resected colon segments. A selection of three lymph nodes is excised from the region around the tumor and is separately measured in the VSM. The iron content in the lymph nodes is quantified from the magnetic moment curve using the Langevin model for superparamagnetism and a bimodal particle size distribution. Adverse, parasitic movements of the sample were successfully reduced by tight fixation of the soft tissue and using a small vibration amplitude. Iron content in the lymph nodes is detected with 0.5 μg accuracy and ranged from 1 to 51 μg. Histological staining confirmed iron presence. The current method of measuring intact biological tissue in a VSM is suitable to show the feasibility and merit of magnetic detection of SLNs in colorectal cancer. For clinical validation of magnetic SLN selection in colorectal cancer, a new magnetometer with high specificity for superparamagnetic nanoparticles is required.

Accuracy of sentinel node biopsy in the staging of non-small cell lung carcinomas: systematic review and meta-analysis of the literature

BACKGROUND

Not all patients with non-small cell lung carcinoma (NSCLC) have mediastinal lymph node involvement and development of less invasive methods for evaluating mediastinal lymph nodes is important. Sentinel node biopsy has been used for NSCLC since 1999 to decrease the need for mediastinal lymph node dissection. In this review, we searched the literature in this regard and reported the results in a meta-analysis format.

METHODS

Medline, SCOPUS, and ISI web of knowledge were searched using: "(lung AND sentinel)" with no date or language limit. Any study with more than 5 patients and enough information to calculate detection rate and sensitivity was included.

RESULTS

Overall 47 and 43 studies (including subgroups) had the criteria for detection rate and sensitivity pooling respectively. Pooled detection rate was 80.6% [76.8-84%] and pooled sensitivity was 87% [83-90%]. Using radiotracers or both radiotracers and dyes had higher detection rate and sensitivity compared to dye alone. Among studies using radiotracers, highest detection rate was in intra-operative peri-tumoral injection group and highest sensitivity was in peri-tumoral pre-operative injection group. Emerging methods of sentinel node surgery including magnetic materials, fluorescent dyes, CT contrast agents, and carbon nano-particles had promising results.

CONCLUSIONS

Sentinel node mapping using radiotracers is a feasible technique for mediastinal lymph node staging of N0 NSCLC patients. Alternative methods of sentinel node mapping are promising and warrant further studies.

Carbon coated superparamagnetic iron oxide nanoparticles for sentinel lymph nodes mapping

Intra-operative lymphatic mapping and sentinel lymph-adenectomy (LM/SL) maps the lymphatic path from the primary tumor to the regional nodes and permits selective excision of the first sentinel lymph nodes. It is a well established technique to detect occult regional node metastases for melanoma patients and breast cancer patients. In continuing attempts to improve accuracy, most surgeons now combine a dye (such as carbon particles) and radiopharmaceuticals when performing LM/SL. We developed a proto-type of carbon coated superparamagnetic iron oxide nanoparticles (SPIO@C) for sentinel lymph nodes mapping. Compared with combining carbon particles and radiopharmaceuticals for performing LM/SL, there are a number of advantages with our approach: I. SPIO is an MRI contrast agent, thus pre-operative MRI may be used for LM/SL instead of gamma camera. There is no radiation associated with MRI, and MRI offers good tissue contrast and detailed cross-sectional images. II. There will be only needed one injection of SPIO@C nanoparticles, instead of administrating two successive injections of radiopharmaceuticals and carbon particles. III. During the operation, an intra-operative MRI scanner can be used, or more conveniently by a simple magnetometer.

Detection of pleural lymph flow using indocyanine green fluorescence imaging in non-small cell lung cancer surgery: a preliminary study

PURPOSE

Lymphatic spread of lung carcinoma to the mediastinum is a key determinant of prognosis. The lymph flow often carries metastases from the pulmonary segment directly into the mediastinal lymph nodes, without passing through the hilar nodes. This phenomenon is termed as "skip metastasis." This study investigated the subpleural lymphatic flow to the mediastinum using indocyanine green (ICG) with a near-infrared fluorescence imaging system.

METHODS

Seventeen patients with lung cancer were enrolled in this study. A 0.3 ml sample of solution containing the fluorescent dye ICG (5 mg/ml) was injected into subpleural sites near the primary tumor. Fluorescence imaging was used to monitor the flow of ICG-containing lymph from the injection site for 5 min. The relationship between the anatomical segment of the primary tumor and the lymphatic flow was assessed.

RESULTS

The lymphatic vessels draining from the injection site were revealed by the bright ICG fluorescence in 14 of the patients (82.4 %). A direct lymphatic flow to the mediastinum was confirmed in 3 of those 14 (21.4 %).

CONCLUSIONS

These findings confirm the direct flow of lymph to the mediastinum without passage through the hilum pulmonis intraoperatively. These preliminary results may provide a valuable clue for further investigations of the mechanisms underlying skip metastasis.

Impact of nodal status and tumor burden in sentinel lymph nodes on the clinical outcomes of cancer patients

The validation of sentinel lymph node (SLN) concept in melanoma and breast cancer has established a new paradigm in cancer metastasis that, in general, cancer cells spread in a orderly fashion from the primary site to the SLNs in the regional nodal basin and then to the distant sites. In this review article, we examine the development of SLN concept in penile carcinoma, melanoma and breast carcinoma and its application to other solid cancers with emphasis of the relationship between micrometastasis in SLNs and clinical outcomes.

Sentinel node and positron emission tomography mapping in lung cancer

Radioguided lymph node mapping can potentially improve staging in locoregional non-small cell lung cancer. This is accomplished by using advanced pathologic techniques to detect micrometastases in selected thoracic lymph nodes. The use of isosulfan blue, technetium-99m and (18)F-fluorodeoxyglucose (FDG) as mapping agents have been reported. Despite several limitations in this technique, it may facilitate the selection of patients for novel therapies, resulting in improved outcomes for lung cancer patients.

Subpleural injection of tracer improves detection of mediastinal sentinel lymph nodes in non-small cell lung cancer

BACKGROUND

The advantages and disadvantages of various tracer injection protocols for sentinel lymph node (SLN) mapping have been extensively discussed in relation to breast and gastric cancer. But no such discussion has taken place in relation to SLN mapping in non-small cell lung cancer. We therefore studied the effect of two tracer injection protocols on SLN mapping in patients with non-small cell lung cancer; of particular interest was the relationship between subpleural tracer injection and identification of mediastinal SLNs.

METHODS

A quadrant injection group (n=49) received 1.6 ml of ferucarbotran by peritumoral quadrant injection after thoracotomy. In the subpleural injection group, the same amount of ferucarbotran was injected into the peritumoral quadrants plus the subpleural region (n=27). SLNs were then detected intraoperatively by measuring the magnetic force within lymph nodes using a hand-held magnetometer. After completing the SLN mapping, lobectomy and hilar and mediastinal lymph node dissection was performed.

RESULTS

The incidence of mediastinal SLNs was significantly higher in the subpleural injection group (45.4%) than in the quadrant injection group (14.6%) (p=0.007). Moreover, nominal logistic regression analysis revealed subpleural injection to be a significant independent factor contributing to detection of mediastinal SLNs (p=0.024, odds ratio 5.26). In the quadrant injection group, mediastinal lymph node metastasis was detected in two patients thought to have nonmetastatic parenchymal SLNs. By contrast, there were no false-negative cases in the subpleural injection group.

CONCLUSION

Subpleural tracer injection significantly improves detection of mediastinal SLNs in non-small cell lung cancer.

Preoperative mapping of lymphatic drainage from the tumor using ferumoxide-enhanced magnetic resonance imaging in clinical submucosal thoracic squamous cell esophageal cancer

BACKGROUND

In thoracic esophageal cancer, lymph node metastases distribute widely from the neck to the abdominal area as a result of a complex periesophageal lymphatic network. The aim of the present study was to evaluate the potential clinical utility of a new method of mapping lymphatic drainage from tumors using ferumoxide-enhanced magnetic resonance imaging (MRI).

METHODS

Twenty-three patients with clinical submucosal thoracic squamous cell esophageal cancer were examined. Ferumoxides were injected endoscopically into the peritumoral submucosal layer, after which their appearance in the lymph nodes in the neck, superior mediastinum, and abdomen was evaluated using MRI.

RESULTS

Flux of ferumoxides from tumors was detected in all 23 patients. Among the 20 patients with middle and lower thoracic esophageal cancers, there was no lymphatic drainage to the neck in 5 (25%) patients, none to the neck and superior mediastinum in 4 (20%), and none to the abdomen in 2 (10%), which could enable the extent of lymph node dissection to be reduced. We diagnosed clinical negative lymph node metastasis (N0) in 17 patients; the remaining 6 patients were diagnosed with clinical lymph node metastasis. Two patients (12%) diagnosed clinical N0, showed pathologic lymph node metastasis. Ferumoxide-enhanced MRI detected an influx of contrast agent into the metastatic node in both patients.

CONCLUSIONS

Ferumoxide-enhanced MRI lymphatic mapping enables detection of the direction and area of lymphatic flux. It thus has the potential to improve our ability to gauge the appropriate extent of treatment in clinical submucosal squamous cell esophageal cancer.

Hyaluronic acid is a useful tool for intraoperative sentinel node detection in gastric cancer surgery

BACKGROUND

We assessed whether a mixture of hyaluronic acid (HA) and dye can facilitate dye-guided sentinel node (SN) mapping in gastric surgery. Although dye-guided, SN-navigated surgery is clinically applied for the treatment of early gastric cancer, there are still some practical problems. Because dyes are carried out from the SN within 20 to 30 minutes, it is sometimes difficult to detect SNs accurately, especially when they are located in a deep area in obese patients.

METHODS

Patent blue or ferumoxides, superparamagnetic iron nanocolloids, with or without HA, were injected into the gastrointestinal tract of the pig, and the time course of dye transfer through the lymphatic system of the pig mesentery was assessed.

RESULTS

When a mixture of HA and patent blue at a volume ratio of 1:4 was injected into the submucosal layer, the time to stain the SN did not differ from that with patent blue alone; however, HA markedly prolonged the time the blue dye was retained in the SN. Patent blue alone stained the efferent lymphatics of the SN and spread to other lymph nodes within 20 minutes after submucosal injection. At the same time point, in contrast, blue stain was restricted to a part of the SN, and the efferent lymphatics were not stained for 2 hours when patent blue was mixed with HA. When a mixture of HA and ferumoxides was used as the tracer, the ferumoxides were still observed in the mesenteric SN even at 2 days after injection. Iron staining showed that Fe was trapped primarily in cells in the peripheral sinus of the SN, suggesting that the iron nanoparticles were mostly incorporated by phagocytic macrophages in the SN within a few hours.

CONCLUSIONS

Our data indicate that a mixture with HA prolongs the stay of a dye tracer in the SN and thus enables easy and accurate detection of the SN. HA may be a useful tool to develop a more sophisticated SN mapping technique.

The Future in Diagnosis and Staging of Lung Cancer

Surgical techniques remain central to the diagnosis and staging of lung cancer. Clinical situations which invoke the role of surgery include the diagnosis of solitary pulmonary masses, staging of the mediastinum, restaging of the mediastinum and the assessment of resectability. The techniques available include cervical mediastinoscopy, anterior mediastinotomy, video-assisted thoracoscopy and different procedures for intra-operative mediastinal lymph node assessment including systematic nodal dissection, lobe-specific nodal dissection and sentinel node mapping. The staging of lung cancer is continuously evolving as technological advances combine with clinical advances to better stratify patients into treatment and prognostic categories and alter pre-operative investigation algorithms. Although most of the surgical techniques have been around for many years, it is their application in future which is likely to change. The increasing use of positron emission tomography/computed tomography fusion imaging is raising the proportion of patients being shown to have additional lesions that could contraindicate surgical treatment but which require tissue confirmation to exclude a false-positive examination. Many such lesions are amenable to the expanding techniques available to the interventional endoscopist. The relationship between the surgeon and the endoscopist must become closer to ensure that the appropriate technique is used at each point in the patient's pathway. The future of surgical techniques will be driven by: (1) developments in screening and imaging, with a likelihood that more early stage cancers will present and may be amenable to minimally invasive surgical approaches with the possibility of a role for robotics and nanotechnology; (2) improvements in neoadjuvant therapies which will demand flawless mediastinal staging and restaging; (3) advances in molecular biology which, whilst currently requiring that surgery provide samples of tumour and lymph node tissue to fully characterize the disease, do hold the promise that ever smaller amounts of tissue will be required and that eventually the genetic fingerprint will provide a biological ultrastaging to perhaps supersede anatomical staging.