Transport and retention of colloidal tracers in regional lymphoscintigraphy in melanoma: influence on lymphatic mapping and sentinel node biopsy

Hot dots - which nodes should be removed in sentinel lymph node biopsy for melanoma?

BACKGROUND

Sentinel lymph node biopsy (SLNB) is a critical staging tool for melanoma patients. The optimal number of lymph nodes removed in SLNB remains unclear. In this study, we retrospectively analysed and tested different criteria for selecting sentinel lymph nodes (SLNs) by radiotracer uptake and blue dye, and their impact on nodal staging. We also evaluated the association between SLN tumour burden and radiotracer uptake.

METHODS

The study population consisted of melanoma patients undergoing SLNB. During the operation all radioactive and blue nodes were removed and sent for histopathological analysis. The ex vivo radioactive count and presence of blue dye of each node were recorded, and these were correlated with presence and size of metastasis in each SLN.

RESULTS

Altogether 175 patients with clinically occult metastasis presented with one or more positive, i.e. metastatic, SLNs. The mean number of lymph nodes removed was 4.5, and the mean number of positive lymph nodes was 1.5 per patient. The most radioactive or hottest node was negative in 38 patients (22%). By removing the hottest node and all nodes with radioactivity >10% of the hottest node, 97% of patients would have been staged correctly. In five patients, metastasis was found solely in a SLN with radioactivity <10% of the hottest node. Of all 267 positive nodes removed, 125 (47%) contained blue dye. Patients with a negative hottest node were associated with lower SLN tumour burden.

CONCLUSIONS

By removing the hottest node and all nodes with radioactivity >10% of the hottest node, 97% of patients with SLN metastases are correctly staged with or without using blue dye.

Recent Applications of the Sentinel Lymph Node Concept: Preliminary Experience in Prostate Cancer

Aims and Background

Following the widespread use of radioguided surgery (RGS) in melanoma and breast cancer, we applied this new surgical strategy to prostate cancer (PC). The aims of this study were 1) to evaluate the accuracy of RGS in the detection of prostatic sentinel lymph nodes (SLN), and 2) to verify if pelvic lymphadenectomy (LAD) is an accurate means to detect solitary micrometastases.

Study design

We investigated 48 patients with PC confirmed by transrectal biopsy who underwent radical prostatectomy and bilateral LAD. A dose of 99mTc-labeled nanocolloid particles was injected into the prostate after needle positioning by ultrasonography. Serial imaging was obtained with a gamma camera, identifying 1) the first radioactive lymph node (sentinel lymph node, SLN); 2) other radioactive lymph nodes, and 3) non-active lymph nodes.

Results

Forty-three SLNs were identified in 48 patients. Twenty SLNs were located at unusual sites with respect to the extent of conventional LAD. Five SLNs were positive for micrometastases and two of these were located outside the usual LAD area. No micrometastases were found in any of the remaining lymph nodes (active and non-active).

Conclusions

These preliminary results are in agreement with the few previous scientific contributions available on this topic and indicate that it is possible to reduce the extent and duration of surgery and necessary to reevaluate the conventional sites of lymphatic drainage.

State of the Art of Sentinel Node Biopsy in Oncology

Sentinel node biopsy has become a standard diagnostic procedure to assess lymph node status of various tumors. The combination of blue dye and a radioactive tracer offers the best chances of identifying the sentinel lymph node. Most progress in the technique of the sentinel node procedure has been made in melanoma and breast cancer. In melanoma, sentinel node biopsy has been introduced as a fundamental procedure for staging. Information on the lymphatic drainage from a melanoma can have a direct impact on the surgery. More recently, the technique has been successfully introduced in the management of breast cancer, in which a large number of unnecessary axillary dissections could be avoided. However, there are many other potential fields of application of the sentinel node biopsy (e.g. endometrial, vulvar, head and neck cancers) that are worthy of investigation. In any case, multicenter trials are required to standardize the procedures, taking into account several variables such as particle size and mode of delivery of the radiotracer, amount of radioactivity administered, number and location of injections, and choice of the hand-held probe. We briefly describe the technical and historical aspects of the sentinel node biopsy and summarize the main clinical trials proposed and/or performed in the field.

Radioisotopic Lymphatic Mapping of the Sentinel Node in Melanoma: Importance of Immunohistochemistry

Background

Elective lymph node dissection (ELND) for patients with malignant melanoma is still controversial. A possible alternative could be biopsy of the first tumor draining lymph node, the sentinel node (SN), which can be identified by means of radionuclide techniques.

Aim

Our study was undertaken to assess the accuracy of lymph node biopsy and to stress the importance of immunohistochemistry (IHC) in the pathological assessment of the SN for improved staging of the primary tumor.

Methods

We performed lymphoscintigraphy (LS) in 183 melanoma patients (89 with melanoma of the legs, 11 of the arms and 83 of the trunk). Our protocol consisted of preoperative peritumoral i.d. injection of 99mTc-labeled microcolloid to define the regional lymphatic basin and identify the sentinel node by means of planar scintigraphy. In 147 of the 183 cases a gamma probe (GP) was used during surgery to trace the SN. Vital blue dye was used during surgery in all cases. The SNs were excised for pathological examination. The pathological status of the SN was defined by means of examination of frozen sections, hematoxylin-eosin staining and immunohistochemistry for S-100 and HMB-45 MAb.

Results

At least one separate focus of activity was identified by LS in 182 out of 183 patients; in all 147 cases where a GP was used, it was successful in tracing the SN. LS with cutaneous mapping of the SN successfully guided the surgical excision in 177 of the 183 cases; in the 7 remaining cases, i.e. 7 out of 83 cases with SNs in the axillary basin, GP was not used and no elective node dissection was performed. Metastases were found in 39 of these 177 cases. In all 39 cases the SNs were the only positive nodes in the basin. Of the 39 metastases 18 were identified by means of frozen section, 12 by means of hematoxylin-eosin, and 9 by means of immunohistochemistry. We therefore emphasize the importance of immunohistochemistry in the pathology of LS for improved staging of the primary tumor.

The inextricable axis of targeted diagnostic imaging and therapy: An immunological natural history approach

In considering the challenges of approaches to clinical imaging, we are faced with choices that sometimes are impacted by rather dogmatic notions about what is a better or worse technology to achieve the most useful diagnostic image for the patient. For example, is PET or SPECT most useful in imaging any particular disease dissemination? The dictatorial approach would be to choose PET, all other matters being equal. But is such a totalitarian attitude toward imaging selection still valid? In the face of new receptor targeted SPECT agents one must consider the remarkable specificity and sensitivity of these agents. (99m)Tc-Tilmanocept is one of the newest of these agents, now approved for guiding sentinel node biopsy (SLNB) in several solid tumors. Tilmanocept has a Kd of 3×10(-11)M, and it specificity for the CD206 receptor is unlike any other agent to date. This coupled with a number of facts, that specific disease-associated macrophages express this receptor (100 to 150 thousand receptors), that the receptor has multiple binding sites for tilmanocept (>2 sites per receptor) and that these receptors are recycled every 15 min to bind more tilmanocept (acting as intracellular "drug compilers" of tilmanocept into non-degraded vesicles), gives serious pause as to how we select our approaches to diagnostic imaging. Clinically, the size of SLNs varies greatly, some, anatomically, below the machine resolution of SPECT. Yet, with tilmanocept targeting, the SLNs are highly visible with macrophages stably accruing adequate (99m)Tc-tilmanocept counting statistics, as high target-to-background ratios can compensate for spatial resolution blurring. Importantly, it may be targeted imaging agents per se, again such as tilmanocept, which may significantly shrink any perceived chasm between the imaging technologies and anchor the diagnostic considerations in the targeting and specificity of the agent rather than any lingering dogma about the hardware as the basis for imaging approaches. Beyond the elements of imaging applications of these agents is their evolution to therapeutic agents as well, and even in the neo-logical realm of theranostics. Characteristics of agents such as tilmanocept that exploit the natural history of diseases with remarkably high specificity are the expectations for the future of patient- and disease-centered diagnosis and therapy.

Dual-modality imaging with 99mTc and fluorescent indocyanine green using surface-modified silica nanoparticles for biopsy of the sentinel lymph node: an animal study

Background

We propose a new approach to facilitate sentinel node biopsy examination by multimodality imaging in which radioactive and near-infrared (NIR) fluorescent nanoparticles depict deeply situated sentinel nodes and fluorescent nodes with anatomical resolution in the surgical field. For this purpose, we developed polyamidoamine (PAMAM)-coated silica nanoparticles loaded with technetium-99m (^99mTc) and indocyanine green (ICG).

Methods

We conducted animal studies to test the feasibility and utility of this dual-modality imaging probe. The mean diameter of the PAMAM-coated silica nanoparticles was 30 to 50 nm, as evaluated from the images of transmission electron microscopy and scanning electron microscopy. The combined labeling with ^99mTc and ICG was verified by thin-layer chromatography before each experiment. A volume of 0.1 ml of the nanoparticle solution (7.4 MBq, except for one rat that was injected with 3.7 MBq, and 1 μg of an ICG derivative [ICG-sulfo-OSu]) was injected submucosally into the tongue of six male Wistar rats.

Results

Scintigraphic images showed increased accumulation of ^99mTc in the neck of four of the six rats. Nineteen lymph nodes were identified in the dissected neck of the six rats, and a contact radiographic study showed three nodes with a marked increase in uptake and three nodes with a weak uptake. NIR fluorescence imaging provided real-time clear fluorescent images of the lymph nodes in the neck with anatomical resolution. Six lymph nodes showed weak (+) to strong (+++) fluorescence, whereas other lymph nodes showed no fluorescence. Nodes showing increased radioactivity coincided with the fluorescent nodes. The radioactivity of 15 excised lymph nodes from the four rats was assayed using a gamma well counter. Comparisons of the levels of radioactivity revealed a large difference between the high-fluorescence-intensity group (four lymph nodes; mean, 0.109% ± 0.067%) and the low- or no-fluorescence-intensity group (11 lymph nodes; mean, 0.001% ± 0.000%, p < 0.05). Transmission electron microscopy revealed that small black granules were localized to and dispersed within the cytoplasm of macrophages in the lymph nodes.

Conclusion

Although further studies are needed to determine the appropriate dose of the dual-imaging nanoparticle probe for effective sensitivity and safety, the results of this animal study revealed a novel method for improved node detection by a dual-modality approach for sentinel lymph node biopsy.

EANM-EORTC general recommendations for sentinel node diagnostics in melanoma

The accurate diagnosis of a sentinel node in melanoma includes a sequence of procedures from different medical specialities (nuclear medicine, surgery, oncology, and pathology). The items covered are presented in 11 sections and a reference list: (1) definition of a sentinel node, (2) clinical indications, (3) radiopharmaceuticals and activity injected, (4) dosimetry, (5) injection technique, (6) image acquisition and interpretation, (7) report and display, (8) use of dye, (9) gamma probe detection, (10) surgical techniques in sentinel node biopsy, and (11) pathological evaluation of melanoma-draining sentinel lymph nodes. If specific recommendations given cannot be based on evidence from original, scientific studies, referral is given to "general consensus" and similar expressions. The recommendations are designed to assist in the practice of referral to, performance, interpretation and reporting of all steps of the sentinel node procedure in the hope of setting state-of-the-art standards for good-quality evaluation of possible spread to the lymphatic system in intermediate-to-high risk melanoma without clinical signs of dissemination.

99mTc Nanocoll: a radiopharmaceutical for sentinel node localisation in breast cancer--in vitro and in vivo results

This study evaluated labelling efficiency and radiochemical purity of (99m)Tc colloid albumin to identify an optimal labelling protocol for sentinel node detection. Results indicate that a 72 h eluate is not recommended for high specific labelling of (99m)Tc colloid albumin. Ex vivo, significantly higher count rates were reached using a 2h eluate in vacuum or nitrogen. Labelling 26 MBq/microg (99m)Tc colloid albumin with a 2 h eluate under nitrogen is recommended because of the ease of labelling.

Sentinel node biopsy using dye and isotope double tracers in early gastric cancer

BACKGROUND

The results of sentinel node (SN) biopsy have been improved by the use of dye and isotope double tracers in melanoma and breast cancer. However, the usefulness of this double tracer technique has not been determined in gastric cancer. The aim of this study was to investigate the possibility of improving SN biopsy results by using double tracers in gastric cancer.

METHODS

Sixty-four gastric adenocarcinoma patients preoperatively diagnosed as cT1N0, were enrolled in the study. (99m)Tc tin colloid was injected by preoperative endoscopy, and lymphoscintigraphy was performed prior to operation. After laparotomy, isosulfan blue was intraoperatively injected using an endoscope. Blue-stained or radioactive nodes were identified and defined as SNs. Gastrectomy with D2 lymphadenectomy was performed in all patients. All dissected lymph nodes were evaluated for metastasis by hematoxylin and eosin staining and immunohistochemistry.

RESULTS

SN detection rates using dye, isotope, or both tracers were 95.3%, 84.4%, and 96.9%, respectively, and their corresponding sensitivities were 52.9%, 52.9%, and 70.6%. In the pT1 subset, the sensitivity of the double tracer was 87.5%; and in a subset of tumors with diameter <4.5 cm, this was also 87.5%.

CONCLUSIONS

These findings confirm that SN biopsy results are improved by using double tracers in gastric cancer and suggest that SN biopsy is suitable in cases of small-sized early gastric cancer.

Histopathologic validation of the sentinel node concept in oral and oropharyngeal squamous cell carcinoma

BACKGROUND

In patients with head and neck squamous cell carcinoma (HNSCC), the presence of lymph node metastases is the most important prognosticator. Sentinel node (SN) biopsy has been shown to be an accurate staging technique for patients with breast cancer and melanoma and might also be suited for patients with HNSCC. This study was undertaken to determine whether the SN concept holds true for HNSCC and could be exploited for SN biopsy.

METHODS

In 22 patients with T2 to T4 N0 oral or oropharyngeal squamous cell carcinoma (SCC) who were scheduled to undergo combined primary tumor excision and elective unilateral (n = 17) or bilateral (n = 5) neck dissection, SN identification was performed the day before surgery by use of lymphoscintigraphy after peritumoral injections of 99mTc-labeled colloidal albumin. After the neck dissection specimens were removed, all SNs, all other radioactive lymph nodes, and all nonradioactive lymph nodes were retrieved for histopathologic analysis, including serial sectioning at 250-microm intervals and immunohistochemical analysis (IHC).

RESULTS

Overall, in 21 (78%) of 27 neck sides, an SN was identified by scintigraphy. Of the six neck sides in which SNs were not identified by scintigraphy, four were from three patients who underwent bilateral neck dissection. In another patient treated by bilateral neck dissection, the SN identified by scintigraphy could not be found in the specimen. In the remaining 20 neck dissection specimens, 23 SNs and 30 additional radioactive lymph nodes could be found. At histologic examination of the 20 neck specimens in which the SN was found, at least one SN was tumor positive in eight cases. In one neck specimen, a metastasis was detected in a nonradioactive lymph node, whereas the SN was tumor free, also at serial sectioning and IHC. In the remaining 11 neck sides in which the SN was tumor negative, none of the other radioactive (n = 13) and none of the nonradioactive (n = 279) lymph nodes contained tumor at histopathologic analysis, including serial sectioning and IHC. The sensitivity of the SN procedure for predicting lymph node metastases, therefore, was 89% (eight of nine neck specimens) when an SN was identified by scintigraphy and found in the specimen. The overall accuracy of the SN procedure for predicting the presence or absence of lymph node metastases in the neck was 95% (19 of 20 neck specimens).

CONCLUSIONS

Our study seems to validate the SN hypothesis for oral and oropharyngeal cancer. The role of SN biopsy in the management of the N0 neck in such patients has yet to be established through prospective trials. SN identification (and thus biopsy) does not seem to be reliable in patients with tumors located in or close to the midline.

Sentinel node biopsy in gastrointestinal-tract cancer

Forty three years after Gould's first description of the sentinel lymph node (SN) technique in malignant tumours of the parotid, sentinel lymph node biopsy (SLNB) has become an invaluable tool for the treatment of solid tumours. In some tumour types, it has been shown to reliably reflect the lymph node (LN) status of the tumour-draining LN basin. In melanoma and breast cancers, it has become a widely accepted element in the routine surgical management of these malignant diseases. In gastrointestinal tumours, the technique is currently under intense investigation. First reports on its application in other solid tumours like non-small cell lung cancer, thyroid carcinoma, oropharyngeal carcinoma, vulvar carcinoma, and Merkel Cell carcinoma of the skin were published more recently. In the following review, we will give a synopsis of the fundamentals of the SN concept and will then proceed to an overview of recent advances of SLNB in gastrointestinal cancers.

Radioguided sentinel lymph node biopsy in patients with malignant cutaneous melanoma: the nuclear medicine contribution

As for other solid tumors, malignant cutaneous melanoma drains in a logical way through the lymphatic system, from the first to subsequent levels. Therefore, the first lymph node encountered (the sentinel node) will most likely be the first to be affected by metastasis, and a negative sentinel node makes it highly unlikely that other nodes in the same lymphatic basin are affected. Sentinel lymph node biopsy distinguishes patients without nodal metastases, who can avoid nodal basin dissection with its associated risk of lymphedema, and those with metastatic involvement who might benefit from additional therapy. This procedure represents a significant advantage as a minimally invasive procedure, considering that only an average 20% of melanoma patients with Breslow thickness between 1.5 and 4 mm harbour metastasis in their sentinel node(s) and are therefore candidates to elective lymph node dissection procedures. The cells that originate cutaneous melanomas are located between dermis and epidermis, a zone that drains to the inner lymphatic network in the reticular dermis, in turn to larger collecting lymphatics in subcutis. Therefore, the optimal modality of interstitial administration of radiocolloids for lymphoscintigraphy and subsequent radioguided sentinel lymph node biopsy is through intradermal/subdermal injection. (99m)Tc-labeled colloids in various size ranges are equally adequate for radioguided sentinel lymph node biopsy in patients with cutaneous melanoma, depending on local experience and availability. For melanomas located in the midline area of the head, neck, and trunk, particular consideration should be given to ambiguous lymphatic drainage, which frequently requires interstitial administration virtually all around the tumor or surgical scar from prior excision of the melanoma. Lymphoscintigraphy is an essential part of radioguided sentinel lymph node biopsy because images are used to direct the surgeon to the sites of the node(s). The sentinel lymph node should have a significantly higher count than that of background (at least 10:1 intraoperatively). After removal of the sentinel node, the surgical bed must be reexamined to ensure that all radioactive sites are identified and removed for analysis. The success rate of radioguidance in localizing the sentinel lymph node in melanoma patients is about 98% in institutions where a high number of procedures are performed, approaching 99% when combined with the vital blue dye technique. The procedure is becoming the standard of care for patients with cutaneous melanoma because of its high prognostic value that has led to include the procedure in the most recent version of the TNM staging system.

The implementation of the sentinel node biopsy as a routine procedure for patients with breast cancer

BACKGROUND

The sentinel node procedure for breast cancer allows for accurate staging of the axilla while the axillary node dissection can be avoided in patients with no sentinel node metastasis. This study describes those patients in whom an axillary dissection is performed, depending on the outcome of the sentinel node procedure, with particular emphasis on the use of strict criteria for the procedure and its practical limitations.

METHODS

Preoperative lymphoscintigraphy was performed in 115 consecutive patients. The sentinel nodes were located with the use of a gamma probe and blue dye. Axillary dissection was performed at the same time when the sentinel node procedure was positive by frozen section or not successful by the criteria used.

RESULTS

The sentinel node procedure was successful in 106 patients, with the sentinel node being both radioactive and blue in 94% of these patients. The frozen section was positive in 21 of 37 patients with sentinel node metastases. Axillary dissection could be avoided in 69 patients.

CONCLUSIONS

The triple technique (with the use of lymphoscintigraphy, the gamma probe, and the blue dye) gives a high success rate of the sentinel node procedure, even when strict criteria for a successful sentinel node procedure are used. Palpation of the open axilla for metastatic nonsentinel nodes is advocated.

Reliability of the sentinel node procedure in melanoma patients: analysis of failures after long-term follow-up

BACKGROUND

The sentinel node (SN) concept assumes that early lymphatic metastases, if present, always are found first in the SN. The aim of this study was to determine the reliability of this procedure by establishing the success rate and number of failed procedures during a follow-up period of at least 2 years.

METHODS

From August 1993 to November 1996, 204 consecutive patients with stage I and II cutaneous melanoma underwent SN biopsy by a triple technique. Preoperatively, all patients underwent (dynamic) lymphoscintigraphy. A gamma probe and blue dye helped localize the SN(s) during surgery, and these nodes subsequently were excised. These lymph nodes were step-sectioned and examined by routine and immunohistochemical staining. If the SN contained tumor cells, a lymphadenectomy was performed at a later date.

RESULTS

The median follow-up time was 42 months. The success rate was 99%. Three patients developed a recurrence in the negative SN basin during follow-up, without simultaneous appearance of (locoregional) metastases.

CONCLUSIONS

With a 99% success rate and a 1.5% rate of failed SN procedures (7% false-negative rate) after a median follow-up of 3.5 years, we concluded that the combined triple technique approach of detecting the SN was a reliable method to accurately identify and retrieve the SN.