Comparing the hybrid fluorescent-radioactive tracer indocyanine green-99mTc-nanocolloid with 99mTc-nanocolloid for sentinel node identification: a validation study using lymphoscintigraphy and SPECT/CT

68Ga-Sienna+ for PET-MRI Guided Sentinel Lymph Node Biopsy: Synthesis and Preclinical Evaluation in a Metastatic Breast Cancer Model

Sentinel lymph node biopsy (SLNB) is commonly performed in cancers that metastasise via the lymphatic system. It involves excision and histology of sentinel lymph nodes (SLNs) and presents two main challenges: (i) sensitive whole-body localisation of SLNs, and (ii) lack of pre-operative knowledge of their metastatic status, resulting in a high number (>70%) of healthy SLN excisions. To improve SLNB, whole-body imaging could improve detection and potentially prevent unnecessary surgery by identifying healthy and metastatic SLNs. In this context, radiolabelled SPIOs and PET-MRI could find applications to locate SLNs with high sensitivity at the whole-body level (using PET) and guide high-resolution MRI to evaluate their metastatic status. Here we evaluate this approach by synthesising a GMP-compatible 68Ga-SPIO (68Ga-Sienna+) followed by PET-MR imaging and histology studies in a metastatic breast cancer mouse model. Methods. A clinically approved SPIO for SLN localisation (Sienna+) was radiolabelled with 68Ga without a chelator. Radiochemical stability was tested in human serum. In vitro cell uptake was compared between 3E.Δ.NT breast cancer cells, expressing the hNIS reporter gene, and macrophage cell lines (J774A.1; RAW264.7.GFP). NSG-mice were inoculated with 3E.Δ.NT cells. Left axillary SLN metastasis was monitored by hNIS/SPECT-CT and compared to the healthy right axillary SLN. 68Ga-Sienna+ was injected into front paws and followed by PET-MRI. Imaging results were confirmed by histology. Results.68Ga-Sienna+ was produced in high radiochemical purity (>93%) without the need for purification and was stable in vitro. In vitro uptake of 68Ga-Sienna+ in macrophage cells (J774A.1) was significantly higher (12 ± 1%) than in cancer cells (2.0 ± 0.1%; P < 0.001). SPECT-CT confirmed metastasis in the left axillary SLNs of tumour mice. In PET, significantly higher 68Ga-Sienna+ uptake was measured in healthy axillary SLNs (2.2 ± 0.9 %ID/mL), than in metastatic SLNs (1.1 ± 0.2 %ID/mL; P = 0.006). In MRI, 68Ga-Sienna+ uptake in healthy SLNs was observed by decreased MR signal in T2/T2*-weighted sequences, whereas fully metastatic SLNs appeared unchanged. Conclusion.68Ga-Sienna+ in combination with PET-MRI can locate and distinguish healthy from metastatic SLNs and could be a useful preoperative imaging tool to guide SLN biopsy and prevent unnecessary excisions.

Novel Near-Infrared Fluorescence-Guided Surgery With Vesicular Stomatitis Virus for Complete Surgical Resection of Osteosarcomas in Mice

Attempts have been made to visualize tumor cells intraoperatively with fluorescence guidance. However, the clear demarcation and complete tumor resection have always been a challenging task. To address this, we have developed a novel fluorescence bioimaging system with vesicular stomatitis virus (VSV) incorporating Katushka, near-infrared fluorescent protein. VSV is tumor-specific owing to the deficiency of antiviral interferon signaling pathways in tumor cells. We aimed to evaluate the tumor specificity of the recombinant VSV-Katushka (rVSV-K) in osteosarcoma cells and to assess the feasibility of complete tumor resection by the rVSV-K fluorescence guidance. In in vitro experiments, mouse and human osteosarcoma cell lines and normal human mesenchymal stem cells were infected with rVSV-K and observed by fluorescence microscopy. Near-infrared fluorescence was observed only in osteosarcoma cells, even at a low-concentration of virus infections. In in vivo experiments, mouse osteosarcoma (LM8) cells were transplanted subcutaneously into the back of immune-competent mice to produce an osteosarcoma, which was then injected with rVSV-K. The areas emitting fluorescence were resected using a bioimaging system. The distance between the surgical and tumor margins of the fluorescence-guided resection with rVSV-K group was significantly larger than that of the non-guided resection groups. The local recurrence rate was significantly lower in the fluorescence-guided resection with rVSV-K group than in the non-guided resection groups. The distant metastasis rate and average survival rate were not significantly different between all groups. These results suggest that the rVSV-K is specific to osteosarcoma cells and enables complete tumor resection of osteosarcomas in mice. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Intraoperative Sentinel Node Mapping in the Colon: Potential and Pitfalls

Sentinel lymph node mapping (SLNM) may play a significant role in future delivery of colon cancer surgery because of an increase in early-stage, node-negative disease due to national bowel cancer screening programmes. Traditionally, colon lymphatic drainage has not been thought relevant as the operative approach cannot be tailored. Recent advances in local and endoscopic risk-reducing interventions for colonic malignancy have caused a rethink in approach. SLNM was initially attempted with blue dye techniques with limited success. Technological improvement has allowed surgeons to use near-infrared (NIR) light and NIR active tracers such as indocyanine green. This review provides an overview of the current status of intraoperative lymph node mapping in the colon, identifies challenges to the delivery of the techniques, and discusses potential solutions that may help SLNM play a role in improving the delivery of surgical care for patients with colon cancer.

Next generation of radiotracers for sentinel lymph node biopsy: What is still necessary to establish new imaging paradigms?

Sentinel lymph node (SLN) biopsy is now the standard of care for regional staging in several solid tumors. The interstitial administration of a radiotracer around the primary tumor provide the possibility to sequentially obtain images with a gamma camera and visualize lymphatic mapping and the SLN. There is, however, a large geographical variability in those radiotracers and nanocolloids ranging from 15-100nm which are most widely employed in Europe, while filtered and unfiltered ^99mTc-sulfur colloid (range 20-1000nm) is usually used in the USA with different drawbacks in its use. The new radiotracer ^99mTc-Tilmanocept, designed specifically for the identification of SLNs and recently becoming commercially available in USA and Europe, appears to have the potency to overcome the shortcomings described for the conventional radiotracers used until now for SLN biopsy and at the same time to transform current imaging paradigms. After delineating the challenges for the next generation of radiotracers, this paper discusses the properties of ^99mTc-Tilmanocept, its validation process for SLN biopsy and its emerging clinical applications in various malignancies.

Synthesis and Preclinical Characterization of the PSMA-Targeted Hybrid Tracer PSMA-I&F for Nuclear and Fluorescence Imaging of Prostate Cancer

The prostate-specific membrane antigen (PSMA)–targeted radiotracers ⁶⁸Ga/¹⁷⁷Lu-PSMA-I&T and ^99mTc-PSMA-I&S (for imaging and surgery) are currently successfully used for clinical PET imaging, radionuclide therapy, and radioguided surgery of metastatic prostate cancer. To additionally exploit the high sensitivity and spatial resolution of fluorescence imaging for improved surgical guidance, a PSMA-I&T–based hybrid tracer, PSMA-I&F (DOTAGA-k(Sulfo-Cy5)-y-nal-k-Sub-KuE), has been developed and evaluated. Methods: The in vitro PSMA-targeting efficiency of PSMA-I&F, the reference PSMA-I&T, and their corresponding ^natGa-/⁶⁸Ga- and ^natLu/¹⁷⁷Lu counterparts was determined in LNCaP cells via competitive binding assays (IC₅₀) and dual-tracer radioligand and fluorescence internalization studies. Biodistribution and small-animal PET imaging studies were performed in CB17 SCID and LNCaP xenograft–bearing SHO mice, respectively, and complemented by intraoperative far-red fluorescence imaging using a clinical laparoscope. Additionally, fully automated serial cryosectioning and fluorescence imaging of 1 tumor-bearing animal as well as PSMA immunohistochemistry and fluorescence microscopy of organ cryosections (tumor, kidney, spleen) were also performed. Results: Compared with the parent PSMA-I&T analogs, the PSMA affinities of PSMA-I&F and its ^natGa-/^natLu-complexes remained high and unaffected by dye conjugation (7.9 < IC₅₀ < 10.5 nM for all ligands). The same was observed for the internalization of ⁶⁸Ga- and ¹⁷⁷Lu-PSMA-I&F. In vivo, blood clearance of ⁶⁸Ga- and ¹⁷⁷Lu-PSMA-I&F was only slightly delayed by high plasma protein binding (94%–95%), and very low accumulation in nontarget organs was observed already at 1 h after injection. Dynamic PET imaging confirmed PSMA-specific (as demonstrated by coinjection of 2-PMPA) uptake into the LNCaP xenograft (4.5% ± 1.8 percentage injected dose per gram) and the kidneys (106% ± 23 percentage injected dose per gram). Tumor-to-background ratios of 2.1, 5.2, 9.6, and 9.6 for blood, liver, intestines, and muscle, respectively, at 1 h after injection led to excellent imaging contrast in ⁶⁸Ga-PSMA-I&F PET and in intraoperative fluorescence imaging. Furthermore, fluorescence imaging of tissue cryosections allowed high-resolution visualization of intraorgan PSMA-I&F distribution in vivo and its correlation with PSMA expression as determined by immunohistochemistry. Conclusion: Thus, with its high PSMA-targeting efficiency and favorable pharmacokinetic profile, ⁶⁸Ga/¹⁷⁷Lu-PSMA-I&F serves as an excellent proof-of-concept compound for the general feasibility of PSMA-I&T–based hybrid imaging. The PSMA-I&T scaffold represents a versatile PSMA-targeted lead structure, allowing relatively straightforward adaptation to the different structural requirements of dedicated nuclear or hybrid imaging agents.

Clinical use of an opto-nuclear probe for hybrid sentinel node biopsy guidance: first results

INTRODUCTION

Guidelines advocate the use of combined detection techniques to achieve optimal results for sentinel node (SN) biopsy. The fluorescent and radioactive (dual-) tracer ICG-^99mTc-nanocolloid has been shown to facilitate SN biopsy in several indications. It was reported that an opto-nuclear probe permitted the detection of near-infrared fluorescence and gamma-rays. The aim of the current study was to evaluate this device in a large patient group and to test it in both open and laparoscopic surgery implications.

METHODS

Thirty-three patients scheduled for SN biopsy with the dual-tracer were retrospectively analyzed. Pre-operative lymphoscintigraphy was performed in all patients; in 18 patients (55%), a SPECT/CT scan was also performed. Radioactive and fluorescent signatures in the SNs were assessed in vivo and ex vivo using the opto-nuclear probe.

RESULTS

One or more SNs were identified in all patients (identification rate 100%). Planar lymphoscintigraphic images revealed 95 hot spots that were considered as SNs. This number increased to 103 SNs when SPECT/CT was used. During surgery, 106 SNs were excised. In vivo, the fluorescence mode of the opto-nuclear probe was able to locate 79 SNs (74.5%). When the gamma-ray detection option of the same probe was used, this number increased to 99 SNs (93.3%). Ex vivo analysis revealed fluorescence in 93.3% of the excised nodes and radioactivity in 95.2%.

CONCLUSIONS

This study underlines the feasibility of using the dual-tracer/opto-nuclear probe combination for SN resections. The use of the opto-nuclear technology has been extended to laparoscopic surgery. This study also underlines the fluorescence tracing can complement traditional radio-tracing approaches.

Tracers for Fluorescence-Guided Surgery: How Elongation of the Polymethine Chain in Cyanine Dyes Alters the Pharmacokinetics of a Dual-Modality c[RGDyK] Tracer

The potential of receptor-mediated fluorescence-based image-guided surgery tracers is generally linked to the near-infrared emission profile and good-manufacturing-production availability of fluorescent dyes. Surprisingly, little is known about the critical interaction between the structural composition of the dyes and the pharmacokinetics of the tracers. In this study, a dual-modality tracer design was used to systematically and quantitatively evaluate the influence of elongation of the polymethine chain in a fluorescent cyanine dye on the imaging potential of a targeted tracer. Methods: As a model system, the integrin marker αvβ3 was targeted using arginylglycylaspartisc acid [RGD]-based vectors functionalized with a 111In-diethylenetriaminepentaacetic acid (DTPA) chelate and a fluorescent dye: (Cy3-(SO3)methyl-COOH [emission wavelength (λem), 580 nm], Cy5-(SO3)methyl-COOH [λem, 680 nm], or Cy7-(SO3)methyl-COOH [λem, 780 nm]). Tracers were analyzed for differences in photophysical properties, serum protein binding, chemical or optical stability, and signal penetration through tissue. Receptor affinities were evaluated using saturation and competition experiments. In vivo biodistribution (SPECT imaging and percentage injected dose per gram of tissue) was assessed in tumor-bearing mice and complemented with in vivo and ex vivo fluorescence images obtained using a clinical-grade multispectral fluorescence laparoscope. Results: Two carbon-atom-step variations in the polymethine chain of the fluorescent cyanine dyes were shown to significantly influence the chemical and photophysical characteristics (e.g., stability, brightness, and tissue penetration) of the hybrid RGD tracers. DTPA-Cy5-(SO3)methyl-COOH-c[RGDyK] structurally outperformed its Cy3 and Cy7 derivatives. Radioactivity-based evaluation of in vivo tracer pharmacokinetics yielded the lowest nonspecific uptake and highest tumor-to-background ratio for DTPA-Cy5-(SO3)methyl-COOH-c[RGDyK] (13.2 ± 1.7), with the Cy3 and Cy7 analogs trailing at respective tumor-to-background ratios of 5.7 ± 0.7 and 4.7 ± 0.7. Fluorescence-based assessment of tumor visibility revealed a similar trend. Conclusion: These findings underline that variations in the polymethine chain lengths of cyanine dyes have a profound influence on the photophysical properties, stability, and in vivo targeting capabilities of fluorescent imaging tracers. In a direct comparison, the intermediate-length dye (Cy5) yielded a superior c[RGDyK] tracer, compared with the shorter (Cy3) and longer (Cy7) analogs.

Melanoma & nuclear medicine: new insights & advances

The contribution of nuclear medicine to management of melanoma patients is increasing. In intermediate-thickness N0 melanomas, lymphoscintigraphy provides a roadmap for sentinel node biopsy. With the introduction of single-photon emission computed tomography images with integrated computed tomography (SPECT/CT), 3D anatomic environments for accurate surgical planning are now possible. Sentinel node identification in intricate anatomical areas (pelvic cavity, head/neck) has been improved using hybrid radioactive/fluorescent tracers, preoperative lymphoscintigraphy and SPECT/CT together with modern intraoperative portable imaging technologies for surgical navigation (free-hand SPECT, portable gamma cameras). Furthermore, PET/CT today provides 3D roadmaps to resect 18F-fluorodeoxyglucose-avid melanoma lesions. Simultaneously, in advanced-stage melanoma and recurrences, 18F-fluorodeoxyglucose-PET/CT is useful in clinical staging and treatment decision as well as in the evaluation of therapy response. In this article, we review new insights and recent nuclear medicine advances in the management of melanoma patients.

Multispectral-Fluorescence Imaging as a Tool to Separate Healthy from Disease-Related Lymphatic Anatomy During Robot-Assisted Laparoscopy

To reduce the invasive nature of extended pelvic lymph node (LN) dissections in prostate cancer, we have developed a multispectral-fluorescence guidance approach that enables discrimination between prostate-draining LNs and lower-limb-draining LNs. Methods: In 5 pigs, multispectral-fluorescence guidance was used on da Vinci Si and da Vinci Xi robots. The animals received fluorescein into the lower limb and indocyanine green-nanocolloid into the prostate. Results: Fluorescein was detected in 29 LNs (average of 3.6 LNs/template), and indocyanine green-nanocolloid was detected in 12 LNs (average of 1.2 LNs/template). Signal intensities appeared equal for both dyes, and no visual overlap in lymphatic drainage patterns was observed. Furthermore, fluorescein supported both the identification of leakage from damaged lymphatic structures and the identification of ureters. Conclusion: We demonstrated that the differences in lymphatic flow pattern between the prostate and lower limbs could be intraoperatively distinguished using multispectral-fluorescence imaging.

Advancements in staging and imaging for penile cancer

PURPOSE OF REVIEW

We review recent advancements in staging and imaging of penile cancer, including surveillance after therapy.

RECENT FINDINGS

For cN0 patients, the sentinel lymph node biopsy is currently considered the preferred way for invasive staging. It has largely replaced other modalities such as staging inguinal lymphadenectomy. Its diagnostic value increases when combined with other staging modalities such as ultrasound with fine-needle aspiration cytology (US-FNAC) or fluorodeoxyglucose-PET with computed tomography (PET/CT). In patients with palpably suspicious nodes (cN+), imaging is more useful. PET/CT has shown good accuracy in a limited number of small studies. US-FNAC can confirm nodal metastatic disease. A staging inguinal lymphadenectomy is of therapeutic value but is associated with significant morbidity. Omitting staging inguinal lymphadenectomy was recently described; one study showed well tolerated use of sentinel lymph node biopsy combined with intraoperative ultrasound-guided resection of suspicious nodes in cN+ patients. Therapeutic inguinal lymphadenectomy was only performed in the 42% of groins with metastases confirmed by disorder. For M-staging, PET/CT has shown good sensitivity, and its role should be further evaluated. Follow-up and surveillance rely on physical examination and US-FNAC.

SUMMARY

Over the past decade, staging and treatment of penile cancer have become less invasive, while survival tends to improve.

Navigating surgical fluorescence cameras using near-infrared optical tracking

Fluorescence guidance facilitates real-time intraoperative visualization of the tissue of interest. However, due to attenuation, the application of fluorescence guidance is restricted to superficial lesions. To overcome this shortcoming, we have previously applied three-dimensional surgical navigation to position the fluorescence camera in reach of the superficial fluorescent signal. Unfortunately, in open surgery, the near-infrared (NIR) optical tracking system (OTS) used for navigation also induced an interference during NIR fluorescence imaging. In an attempt to support future implementation of navigated fluorescence cameras, different aspects of this interference were characterized and solutions were sought after. Two commercial fluorescence cameras for open surgery were studied in (surgical) phantom and human tissue setups using two different NIR OTSs and one OTS simulating light-emitting diode setup. Following the outcome of these measurements, OTS settings were optimized. Measurements indicated the OTS interference was caused by: (1) spectral overlap between the OTS light and camera, (2) OTS light intensity, (3) OTS duty cycle, (4) OTS frequency, (5) fluorescence camera frequency, and (6) fluorescence camera sensitivity. By optimizing points 2 to 4, navigation of fluorescence cameras during open surgery could be facilitated. Optimization of the OTS and camera compatibility can be used to support navigated fluorescence guidance concepts.

The best of both worlds: a hybrid approach for optimal pre- and intraoperative identification of sentinel lymph nodes

Purpose

Hybrid image-guided surgery technologies such as combined radio- and fluorescence-guidance are increasingly gaining interest, but their added value still needs to be proven. In order to evaluate if and how fluorescence-guidance can help realize improvements beyond the current state-of-the-art in sentinel node (SN) biopsy procedures, use of the hybrid tracer indocyanine green (ICG)-^99mTc-nancolloid was evaluated in a large cohort of patients.

Patients and methods

A prospective trial was conducted (n = 501 procedures) in a heterogeneous cohort of 495 patients with different malignancies (skin malignancies, oral cavity cancer, penile cancer, prostate cancer and vulva cancer). After injection of ICG-^99mTc-nanocolloid, SNs were preoperatively identified based on lymphoscintigraphy and SPECT/CT. Intraoperatively, SNs were pursued via gamma tracing, visual identification (blue dye) and/or near-infrared fluorescence imaging during either open surgical procedures (head and neck, penile, vulvar cancer and melanoma) or robot assisted laparoscopic surgery (prostate cancer). As the patients acted as their own control, use of hybrid guidance could be compared to conventional radioguidance and the use of blue dye (n = 300). This was based on reported surgical complications, overall survival, LN recurrence free survival, and false negative rates (FNR).

Results

A total of 1,327 SN-related hotspots were identified on 501 preoperative SPECT/CT scans. Intraoperatively, a total number of 1,643 SNs were identified based on the combination of gamma-tracing (>98%) and fluorescence-guidance (>95%). In patients wherein blue dye was used (n = 300) fluorescence-based SN detection was superior over visual blue dye-based detection (22–78%). No adverse effects related to the use of the hybrid tracer or the fluorescence-guidance procedure were found and outcome values were not negatively influenced.

Conclusion

With ICG-^99mTc-nanocolloid, the SN biopsy procedure has become more accurate and independent of the use of blue dye. With that, the procedure has evolved to be universal for different malignancies and anatomical locations.

Electronic supplementary material

The online version of this article (10.1007/s00259-018-4028-x) contains supplementary material, which is available to authorized users.

From interventionist imaging to intraoperative guidance: New perspectives by combining advanced tools and navigation with radio-guided surgery

The integration of medical imaging technologies into diagnostic and therapeutic approaches can provide a preoperative insight into both anatomical (e.g. using computed tomography, magnetic resonance imaging, or ultrasound), as well as functional aspects (e.g. using single photon emission computed tomography, positron emission tomography, lymphoscintigraphy, or optical imaging). Moreover, some imaging modalities are also used in an interventional setting (e.g. computed tomography, ultrasound, gamma or optical imaging) where they provide the surgeon with real-time information during the procedure. Various tools and approaches for image-guided navigation in cancer surgery are becoming feasible today. With the development of new tracers and portable imaging devices, these advances will reinforce the role of interventional molecular imaging.

A pilot study to assess near infrared laparoscopy with indocyanine green (ICG) for intraoperative sentinel lymph node mapping in early colon cancer

BACKGROUND

Previous attempts at sentinel lymph node (SLN) mapping in colon cancer have been compromised by ineffective tracers and the inclusion of advanced disease. This study evaluated the feasibility of fluorescence detection of SLNs with indocyanine green (ICG) for lymphatic mapping in T1/T2 clinically staged colonic malignancy.

METHODS

Consecutive patients with clinical T1/T2 stage colon cancer underwent endoscopic peritumoral submucosal injection of indocyanine green (ICG) for fluorescence detection of SLN using a near-infrared (NIR) camera. All patients underwent laparoscopic complete mesocolic excision surgery. Detection rate and sensitivity of the NIR-ICG technique were the study endpoints.

RESULTS

Thirty patients mean age = 68 years [range = 38-80], mean BMI = 26.2 (IQR = 24.7-28.6) were studied. Mesocolic sentinel nodes (median = 3/patient) were detected by fluorescence within the standard resection field in 27/30 patients. Overall, ten patients had lymph node metastases, with one of these patients having a failed SLN procedure. Of the 27 patients with completed SLN mapping, nine patients had histologically positive lymph nodes containing malignancy. 3/9 had positive SLNs with 6 false negatives. In five of these false negative patients, tumours were larger than 35 mm with four also being T3/T4.

CONCLUSION

ICG mapping with NIR fluorescence allowed mesenteric detection of SLNs in clinical T1/T2 stage colonic cancer. CLINICALTRIALS.GOV: ID: NCT01662752.

Local resection of the stomach for gastric cancer

The local resection of the stomach is an ideal method for preventing postoperative symptoms. There are various procedures for performing local resection, such as the laparoscopic lesion lifting method, non-touch lesion lifting method, endoscopic full-thickness resection, and laparoscopic endoscopic cooperative surgery. After the invention and widespread use of endoscopic submucosal dissection, local resection has become outdated as a curative surgical technique for gastric cancer. Nevertheless, local resection of the stomach in the treatment of gastric cancer in now expected to make a comeback with the clinical use of sentinel node navigation surgery. However, there are many issues associated with local resection for gastric cancer, other than the normal indications. These include gastric deformation, functional impairment, ensuring a safe surgical margin, the possibility of inducing peritoneal dissemination, and the associated increase in the risk of metachronous gastric cancer. In view of these issues, there is a tendency to regard local resection as an investigative treatment, to be applied only in carefully selected cases. The ideal model for local resection of the stomach for gastric cancer would be a combination of endoscopic full-thickness resection of the stomach using an ESD device and hand sutured closure using a laparoscope or a surgical robot, for achieving both oncological safety and preserved functions.

A promising dual mode SPECT/CT imaging platform based on 99mTc-labeled multifunctional dendrimer-entrapped gold nanoparticles

Multifunctional ^99mTc-labeled dendrimer-entrapped gold nanoparticles (^99mTc-Au DENPs) were designed and synthesized. Our results show that the type of surface groups (acetyl or hydroxyl) significantly impact the biodistribution profile of the ^99mTc-Au DENPs, thereby allowing for preferential SPECT/CT imaging of different organs.

Role of ICG-99mTc-nanocolloid for sentinel lymph node detection in cervical cancer: a pilot study

PURPOSE

Sentinel lymph node biopsy (SLNB) can be used for nodal staging in early cervical cancer. For this purpose, the tracers most commonly used are radiotracers based on technetium. For the last decade, indocyanine green (ICG) has been used as a tracer for SLNB in other malignancies with excellent results and, more recently, a combination of ICG and a radiotracer has been shown to have the advantages of both tracers. The aim of this study was to evaluate the role of ICG-^99mTc-nanocolloid in SLN detection in patients with cervical cancer.

METHODS

This prospective study included 16 patients with cervical cancer. The hybrid tracer was injected the day (19-21 h) before surgery for planar and SPECT/CT lymphoscintigraphy. Blue dye was administered periorificially in 14 patients. SLNs were removed according to their distribution on lymphoscintigraphy and when radioactive, fluorescent and/or stained with blue dye. Nodal specimens were pathologically analysed for metastases including by immunochemistry.

RESULTS

Lymphoscintigraphy and SPECT/CT showed drainage in all patients. A total of 69 SLNs were removed, of which 66 were detected by their radioactivity signal and 67 by their fluorescence signal. Blue dye identified only 35 SLNs in 12 of the 14 patients (85.7%). All patients showed bilateral pelvic drainage. Micrometastases were diagnosed in two patients, and were the only lymphatic nodes involved.

CONCLUSIONS

SLNB with ICG-^99mTc-nanocolloid is feasible and safe in patients with early cervical cancer. This hybrid tracer provided bilateral SLN detection in all patients and a higher detection rate than blue dye, so it could become an alternative to the combined technique.

Laparoscopic sentinel node navigation surgery for early gastric cancer

Currently, the most accurate method for identifying lymph node metastasis is intraoperative diagnosis by sentinel node (SN) biopsy. Based on the SNNS study-a recent large-scale, nationwide, multicenter prospective study-the SN concept seems to be scientifically valid in patients with early gastric cancer. SN biopsy is a multistep technique consisted of six essential elements: indication, the selection of a tracer, a proper tracer injection method, the objective detection of SNs, a reliable biopsy technique, and the precise detection of nodal metastasis. For SN biopsy of gastric cancer, these elements have been validated as follows: the indication should be limited to clinical T1 less than 4 cm in diameter; combination mapping with radioactive colloid and blue dye is used as the standard; and endoscopic submucosal injection is the standard tracer injection. Detection of SNs and a reliable biopsy technique are enabled by adaptation of lymphatic basin dissection, a proper biopsy technique for gastric cancer. Lymphatic basin dissection is a selective lymphadenectomy procedure for dissecting basins en bloc, collecting lymph nodes and lymphatic vessels stained with dye. Lymphatic basin dissection is superior to the ordinary pick-up method, not only for minimizing the rate of missed SNs, but also in terms of oncological safety as it complements an intraoperative frozen section diagnosis by serving as a backup dissection. Moreover, indocyanine green (ICG) fluorescence mapping has been developed in recent years. ICG fluorescence mapping is superior because of its high sensitivity and signal stability. Moreover, it is feasible for both open and laparoscopic gastrectomy in treating early gastric cancer. SN biopsy has brought dramatic changes to laparoscopic surgery for early gastric cancer. With laparoscopic SN biopsy using ICG fluorescence navigation, laparoscopic surgery for early gastric cancer has changed from the uniform standard gastrectomy with D1+ into a tailor-made function-preserving surgical procedure, such as local resection with lymphatic basin dissection.

Gamma probe and ultrasound guided fine needle aspiration cytology of the sentinel node (GULF) trial - overview of the literature, pilot and study protocol

BACKGROUND

Sentinel node (SN) biopsy (SNB) detects clinically occult metastases of breast cancer and melanoma in 20-30%. Wound infections, seroma and lymph edema occur in up to 10%. Targeted ultrasound (US) of the SN, (with fine needle aspiration cytology (FNAC) if appropriate) has been investigated as a minimally invasive alternative, but reported sensitivity rates are too low to replace SNB. Our hypothesis is that the use of a handheld gamma probe concomitant with US may improve sensitivity. Our aim is to provide an overview of the current literature on preoperative nodal staging of clinical N0 melanoma patients, report on a pilot, and present a study protocol for a minimally invasive alternative to the SNB: Gamma probe and Ultrasound guided Fine needle aspiration cytology of the sentinel node (GULF trial).

METHODS

The GULF trial is a multicenter open single arm observational trial. Newly diagnosed cT1b-4N0M0 cutaneous melanoma or cT1-3N0M0 breast cancer patients, aged >18 years, presenting for SNB are eligible. 120 patients will be included for preoperative targeted gamma probe guided US and FNAC of the SN. Afterwards all patients proceed to surgical SNB. Primary endpoint is the sensitivity of FNAC. Secondary endpoints include SN identification rate and the histopathological compatibility of Core Needle Biopsy and FNAC vs. SNB. Secondary endpoints were investigated in a pilot with 10 FNACs and marker placements, and 10 FNACs combined with Core Needle Biopsy.

RESULTS

A pilot in 20 patients showed that SN identification rate was 90%, supporting the feasibility of this technique.

DISCUSSION

There is broad experience with US (in combination with FNAC) prior to SNB, but sensitivity and specificity are too low to completely abandon SNB. Promising alternative techniques potentially will replace SNB in the future but more evidence is needed in the form of prospective studies. Accurate identification of the SN for US-FNAC has been proven feasible in our pilot. When adequate sensitivity can be reached, US-FNAC provides a minimally invasive alternative for the surgical SNB procedure.

TRIAL REGISTRATION

The GULF trial is registered in the Netherlands Trial Registry (NTR), ID: NRT5193 . May 1st 2015.

A Multimodality Hybrid Gamma-Optical Camera for Intraoperative Imaging

The development of low profile gamma-ray detectors has encouraged the production of small field of view (SFOV) hand-held imaging devices for use at the patient bedside and in operating theatres. Early development of these SFOV cameras was focussed on a single modality—gamma ray imaging. Recently, a hybrid system—gamma plus optical imaging—has been developed. This combination of optical and gamma cameras enables high spatial resolution multi-modal imaging, giving a superimposed scintigraphic and optical image. Hybrid imaging offers new possibilities for assisting clinicians and surgeons in localising the site of uptake in procedures such as sentinel node detection. The hybrid camera concept can be extended to a multimodal detector design which can offer stereoscopic images, depth estimation of gamma-emitting sources, and simultaneous gamma and fluorescence imaging. Recent improvements to the hybrid camera have been used to produce dual-modality images in both laboratory simulations and in the clinic. Hybrid imaging of a patient who underwent thyroid scintigraphy is reported. In addition, we present data which shows that the hybrid camera concept can be extended to estimate the position and depth of radionuclide distribution within an object and also report the first combined gamma and Near-Infrared (NIR) fluorescence images.

Radiolabelled Polymeric Materials for Imaging and Treatment of Cancer: Quo Vadis?

Owing to their tunable blood circulation time and suitable plasma stability, polymer-based nanomaterials hold a great potential for designing and utilising multifunctional nanocarriers for efficient imaging and effective treatment of cancer. When tagged with appropriate radionuclides, they may allow for specific detection (diagnosis) as well as the destruction of tumours (therapy) or even customization of materials, aiming to both diagnosis and therapy (theranostic approach). This review provides an overview of recent developments of radiolabelled polymeric nanomaterials (natural and synthetic polymers) for molecular imaging of cancer, specifically, applying nuclear techniques such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT). Different approaches to radiolabel polymers are evaluated from the methodical radiochemical point of view. This includes new bifunctional chelating agents (BFCAs) for radiometals as well as novel labelling methods. Special emphasis is given to eligible strategies employed to evade the mononuclear phagocytic system (MPS) in view of efficient targeting. The discussion encompasses promising strategies currently employed as well as emerging possibilities in radionuclide-based cancer therapy. Key issues involved in the clinical translation of radiolabelled polymers and future scopes of this intriguing research field are also discussed.

Sentinel Lymph Node Biopsy in Cutaneous Melanoma: Standard and New Technical Procedures and Clinical Advances. A Systematic Review of the Literature

Melanoma is an important public health problem, and its incidence is increasing worldwide. The disease status of regional lymph nodes is the most important prognostic factor in early-stage melanoma patients. Sentinel lymph node biopsy (SLNB) was introduced in the early 1990s as a less invasive procedure than complete lymph node dissection to allow histopathologic evaluation of the "sentinel lymph node" (SLN), which is the first node along the lymphatic pathway from a primary tumor. Sentinel lymph node biopsy has minimal complication risks compared with standard complete lymph node dissection. Currently, SLNB is the accepted method for staging patients with clinically node-negative cutaneous melanoma and provides the most powerful prognostic information by evaluating the nodal basin status. The current practice of SLNB consists of the injection of Tc-labeled radiopharmaceutical, preoperative lymphoscintigraphy with the possibility of using the SPECT/CT hybrid imaging, and intraoperative SLN localization using a handheld gamma probe with or without the use of blue dye. Recently, the SLN localization and detection have been enhanced with the use of new tracers and new intraoperative devices, which have demonstrated to be particularly useful in melanomas of the head and neck region and in area of complex anatomy. Despite these important advances in the technology and the increasing experience in SLN mapping, major research centers have reported a false-negative rate higher than 15%. This relatively high false-negative rate, greater than those reported in the initial validation studies, points out the importance for the nuclear medicine community to continuously improve their knowledge on the biological behavior of melanoma and to improve the technical aspects that may allow more precise staging. For the SLNB procedure to be accurate, it is of critical importance that all "true" SLNs are identified and removed for examination. The aim of this article is to provide general information about the SLNB procedure in clinical practice highlighting the importance of standardization and accuracy of SLN identification in the light of the most recent technical innovations.

Feasibility of Real-Time Near-Infrared Fluorescence Tracer Imaging in Sentinel Node Biopsy for Oral Cavity Cancer Patients

Background

Sentinel node biopsy (SNB) is an established method in oral squamous cell carcinoma (OSCC) for staging the cN0 neck and to select patients who will benefit from a neck dissection. Near-infrared fluorescence (NIRF) imaging has the potential to improve the SNB procedure by facilitating intraoperative visual identification of the sentinel lymph node (SN). The purpose of this study was to evaluate the feasibility of fluorescence tracer imaging for SN detection in conjunction with conventional radio-guided technique.

Methods

Prospective study of patients with primary OSCC planned for tumor resection and SNB. Thirty patients were injected peritumorally with a bimodal tracer (ICG-^99mTc-Nanocoll) followed by lymphoscintigraphy and SPECT/CT to define the SNs and their anatomical location preoperatively. SNs were detected intraoperatively with a hand-held gamma-probe and a hand-held NIRF camera.

Results

In 29 of 30 subjects (97%), all preoperatively defined SNs could be identified intraoperatively using a combination of radioactive and fluorescence guidance. A total of 94 SNs (mean 3, range 1–5) that were both radioactive and fluorescent ex vivo were harvested. Eleven of 94 SNs (12%) could only be identified in vivo using NIRF imaging, and the majority of those were located in level 1 close to the primary tumor.

Conclusions

A combined fluorescent and radioactive tracer for SNB is feasible, and the additional use of NIRF imaging may improve the accuracy of SN identification in oral cancer patients. Intraoperative fluorescence guidance seems of particular value when SNs are located in close proximity to the injection site.

Radioguided surgery and the GOSTT concept: From pre-operative image and intraoperative navigation to image-assisted excision

Radio-guided surgery has been developed for application in those disease scheduled for surgical management, particularly in areas of complex anatomy. This is based on the use of pre-operative scintigraphic planar, tomographic and fused SPECT/CT images, and the possibility of 3D reconstruction for the subsequent intraoperative locating of active lesions using handheld devices (detection probes, gamma cameras, etc.). New tracers and technologies have also been incorporated into these surgical procedures. The combination of visual and acoustic signals during the intraoperative procedure has become possible with new portable imaging modalities. In daily practice, the images offered by these techniques and devices combine perioperative nuclear medicine imaging with the superior resolution of additional optical guidance in the operating room. In many ways they provide real-time images, allowing accurate guidance during surgery, a reduction in the time required for tissue location and an anatomical environment for surgical recognition. All these approaches have been included in the concept known as (radio) Guided intraOperative Scintigraphic Tumour Targeting (GOSTT). This article offers a general view of different nuclear medicine and allied technologies used for several GOSTT procedures, and illustrates the crossing of technological frontiers in radio-guided surgery.

Beyond penile cancer, is there a role for sentinel node biopsy in urological malignancies?

This review aims to discuss the current state-of-the-art of sentinel node (SN) mapping in urological malignancies. The principles and methodological aspects of lymphatic mapping and SN biopsy in urological malignancies are reviewed. Literature search was restricted to English language. The references of the retrieved articles were examined to identify additional articles. The review also includes meta-analyses published in the past 5 years. SN biopsy for penile cancer is recommended by the European Association of Urology as the preferred staging tool for clinically node-negative patients with at least T1G2 tumours (level of evidence 2a, Grade B). The feasibility of SN biopsy in prostate cancer has been repeatedly demonstrated and its potential value is increasingly being recognised. However, conclusive prospective clinical data as well as consensus on methodology and patient selection are still lacking. For bladder, renal and testicular cancer, only few studies have been published, and concerns around high false-negative rates remain. Throughout the years, the uro-oncological field has portrayed a pivotal role in the development of the SN concept. Recent advances such as hybrid tracers and novel intraoperative detection tools such as fluorescence and portable gamma imaging will hopefully encourage prospectively designed clinical trials which can further substantiate the potential of the SN approach in becoming an integral part of staging in urological malignancies beyond penile cancer.

(99m)Tc-Labeled Multifunctional Low-Generation Dendrimer-Entrapped Gold Nanoparticles for Targeted SPECT/CT Dual-Mode Imaging of Tumors

Development of cost-effective and highly efficient nanoprobes for targeted tumor single-photon emission computed tomography (SPECT)/computed tomography (CT) dual-mode imaging remains a challenging task. Here, multifunctional dendrimer-entrapped gold nanoparticles (Au DENPs) modified with folic acid (FA) and labeled with (99m)Tc were synthesized for targeted dual-mode SPECT/CT imaging of tumors. Generation 2 (G2) poly(amidoamine) (PAMAM) dendrimers (G2-NH2) conjugated with cyclic diethylenetriamine pentaacetic anhydride (cDTPAA) via an amide linkage and FA via a spacer of polyethylene glycol (PEG) were used for templated synthesis of Au core NPs, followed by labeling of (99m)Tc via chelation. The thus created multifunctional Au DENPs were well-characterized. It is shown that particles with an average Au core diameter of 1.6 nm can be dispersed in water, display stability under different conditions, and are cytocompatible in the studied concentration range. Further results demonstrate that the multifunctional nanoprobe is able to be utilized for targeted SPECT/CT dual-mode imaging of cancer cells having FA receptor (FAR)-overexpression in vitro and the established subcutaneous tumor model in vivo within a time frame up to 4 h. The formed multifunctional Au DENPs synthesized using dendrimers of low-generation may be employed as an effective and economic nanoprobe for SPECT/CT imaging of different types of FAR-expressing tumors.

Preparation study of indocyanine green-rituximab: A new receptor-targeted tracer for sentinel lymph node in breast cancer

An appropriate receptor-targeted tracer for sentinel lymph node biopsy (SLNB) was prepared. We combined the fluorescence tracer (Indocyanine green, ICG) with Rituximab (a chimeric human/murine monoclonal antibody targeting the CD20 antigen on the surface of lymphocyte) directly to produce a new tracer (ICG-Rituximab). When the new tracer drains to the lymph node, Rituximab will combine with CD20 receptor on the B-cell surface in the lymph node. If the statue of antibody-receptor connection does not reach saturation, the number of Rituximab is less than CD20. With this appropriate injection dose, the new tracer could only stay in sentinel lymph node (SLN) and make it imaging. Positive fluorescence SLN was detected 12 minutes after injection with no other organs imaging. The imaging of SLN was stable and clear for 20-24 hours. Due to SLN stained with more ICG than the lymphatic vessel, the fluorescence situation of SLN would be brighter than the vessel. The surgeon can detect the positive fluorescence SLN easily without following the fluorescence imaging lymphatic vessel. The results of our preliminary study showed that the new tracer might be useful for improving SLN imaging and worth further clinical study. SLNB with the new tracer could be a convenient method for detecting SLN and would become a standard performance in clinical practice.

Contemporary use of sentinel lymph node biopsy in the head and neck

Sentinel lymph node biopsy has become a well-established and commonplace practice in many oncologic disease sites as a means to stage the regional lymphatics, avoid unnecessary surgery and decrease patient morbidity. In the head and neck, its role is well established for cutaneous melanoma with proven fidelity and survival benefit. Its role in use for other sites such as oral cavity carcinoma continues to develop with promising results from several recent trials. Although not widely adopted, the potential benefits of sentinel lymph node biopsy in the management of oral cavity carcinoma are apparent. Refinements in technology and protocols including development of novel radiopharmaceutical tracers, routine incorporation of detailed anatomic imaging, increasing surgeon experience and development of new intraoperative identification aids will likely lead to improvements in the use and accuracy of this technique.

Localization of the Sentinel Lymph Node in Melanoma Without Blue Dye

OBJECTIVE

The purpose of this study was to assess regional recurrence rates of patients who underwent sentinel lymph node biopsy (SLNB) using radiocolloid guidance alone.

BACKGROUND

Isosulfan blue dye is commonly used along with Tc99-labeled radiocolloid localization in SLNB for melanoma. Blue dye has, however, been associated with allergic reactions, long-term staining of skin, and increased cost. We hypothesized that the rate of regional recurrence when SLNB is performed with radiocolloid alone would be comparable to established reports using both radiocolloid and blue dye.

METHODS

A prospectively collected database was retrospectively queried for patients who underwent SLNB for melanoma during the years 2005 through 2008. Data collected included patient demographics, primary lesion characteristics, operative details, and recurrence. The primary outcome was the rate of recurrence within the biopsied basin after negative SLNB's performed without isosulfan blue dye.

RESULTS

In 215 patients, 279 nodal basins were identified. All patients underwent successful radiocolloid localization, and positive sentinel nodes were found in 40 patients (18.6%). Six of 175 patients with a negative SLNB developed a regional node recurrence as the first site of metastasis (3.4%). Among all 215 patients, 44 experienced recurrence of any kind (20.5%). Higher mitotic rate and Breslow depth were significantly associated with likelihood of recurrence.

CONCLUSIONS

Success rates, node positivity rates, and rates of regional recurrence after SLNB for melanoma using radiocolloid alone are acceptable and similar to those of prior reports using blue dye plus radiocolloid.

Optimal settings and accuracy of indocyanine green fluorescence imaging for sentinel node biopsy in early gastric cancer

Indocyanine green (ICG) fluorescence imaging represents a promising method for sentinel node (SN) biopsy in laparoscopic gastric surgery due to its signal stability. In the present study, the suitability and optimal settings of ICG fluorescence imaging for SN biopsy in early gastric cancer were determined. Patients with single primary superficial-type adenocarcinoma of the stomach, lesions <5 cm in diameter, and no evident nodal metastasis and out of indication for endoscopic submucosal dissection were enrolled. The day prior to surgery, ICG solution was endoscopically injected into four quadrants of the submucosal layer of the tumor. The Photodynamic Eye was used to detect ICG fluorescence. Bright nodes were defined as clearly fluorescent nodes. A total of 72 patients were enrolled; 11 cases presented with metastasis, and of these, 10 could be diagnosed by bright node biopsy. The adequate concentration and injection volume of ICG was determined to be 50 µg/ml (×100) and 0.5 mlx4 points, respectively. There was 1 false-negative case, and this was attributed to the failure of the frozen section diagnosis. These results suggested that ICG fluorescence imaging for SN biopsy in laparoscopic surgery for early gastric cancer is feasible. However, a weakness of ICG fluorescence imaging is the subjectivity of bright node evaluation.

Hybrid radioguided occult lesion localization (hybrid ROLL) of (18)F-FDG-avid lesions using the hybrid tracer indocyanine green-(99m)Tc-nanocolloid

PURPOSE

To assess if combined fluorescence- and radio-guided occult lesion localization (hybrid ROLL) is feasible in patients scheduled for surgical resection of non-palpable (18)F-FDG-avid lesions on PET/CT.

METHODS

Four patients with (18)F-FDG-avid lesions on follow-up PET/CT that were not palpable during physical examination but were suspected to harbor metastasis were enrolled. Guided by ultrasound, the hybrid tracer indocyanine green (ICG)-(99m)Tc-nanocolloid was injected centrally in the target lesion. SPECT/CT imaging was used to confirm tracer deposition. Intraoperatively, lesions were localized using a hand-held gamma ray detection probe, a portable gamma camera, and a fluorescence camera. After excision, the gamma camera was used to check the wound bed for residual activity.

RESULTS

A total of six (18)F-FDG-avid lymph nodes were identified and scheduled for hybrid ROLL. Comparison of the PET/CT images with the acquired SPECT/CT after hybrid tracer injection confirmed accurate tracer deposition. No side effects were observed. Combined radio- and fluorescence-guidance enabled localization and excision of the target lesion in all patients. Five of the six excised lesions proved tumor-positive at histopathology.

CONCLUSION

The hybrid ROLL approach appears to be feasible and can facilitate the intraoperative localization and excision of non-palpable lesions suspected to harbor tumor metastases. In addition to the initial radioguided detection, the fluorescence component of the hybrid tracer enables high-resolution intraoperative visualization of the target lesion. The procedure needs further evaluation in a larger cohort and wider range of malignancies to substantiate these preliminary findings.

Indocyanine green delivery systems for tumour detection and treatments

Indocyanine green (ICG) is a cyanine compound that displays fluorescent properties in the near infrared region. This dye is employed for numerous indications but nowadays its major application field regards tumour diagnosis and treatments. Optical imaging by near infrared fluorescence provides news opportunities for oncologic surgery. The imaging of ICG can be useful for intraoperative identification of several solid tumours and metastases, and sentinel lymph node detection. In addition, ICG can be used as an agent for the destruction of malignant tissue, by virtue of the production of reactive oxygen species and/or induction of a hyperthermia effect under irradiation. Nevertheless, ICG shows several drawbacks, which limit its clinical application. Several formulative strategies have been studied to overcome these problems. The rationale of the development of ICG containing drug delivery systems is to enhance the in vivo stability and biodistribution profile of this dye, allowing tumour accumulation and resulting in better efficacy. In this review, ICG containing nano-sized carriers are classified based on their chemical composition and structure. In addition to nanosystems, different formulations including hydrogel, microsystems and others loaded with ICG will be illustrated. In particular, this report describes the preparation, in vitro characterization and in vivo application of ICG platforms for cancer imaging and treatment. The promising results of all systems confirm their clinical utility but further studies are required prior to evaluating the formulations in human trials.