Sentinel lymphadenectomy for melanoma--is it a substitute for elective lymphadenectomy?

Role of sentinel lymph node biopsy as a staging procedure in patients with melanoma: A critical appraisal

Worldwide, sentinel node (SN) biopsy for accurate staging is now part of the standard work-up of patients with melanomas ≥1.0 mm Breslow thickness, as it is for staging patients with breast cancer. Nuclear medicine imaging and surgical techniques have evolved to such a degree that a SN can be identified and removed in virtually every patient. Nevertheless, some opposition to a routine SN biopsy remains, perhaps due to a failure to appreciate the serious implications of incomplete or inaccurate staging. Guided by a critical appraisal of the available evidence, this review elucidates the definition of an SN, discusses the sensitivity and specificity of the information it provides, emphasises that it is a minor staging procedure that can lead to improved survival when followed by appropriate therapy, and explains the necessarily unconventional and complex design of the only randomised trial that addresses this subject. It also describes other benefits and risks of an SN biopsy and outlines its role in current melanoma management.

New approach to anal cancer: Individualized therapy based on sentinel lymph node biopsy

Oncological treatment is currently directed toward a tailored therapy concept. Squamous cell carcinoma of the anal canal could be considered a suitable platform to test new therapeutic strategies to minimize treatment morbidity. Standard of care for patients with anal canal cancer consists of a combination of radiotherapy and chemotherapy. This treatment has led to a high rate of local control and a 60% cure rate with preservation of the anal sphincter, thus replacing surgical abdominoperineal resection. Lymph node metastases represent a critical independent prognostic factor for local recurrence and survival. Mesorectal and iliac lymph nodes are usually included in the radiation field, whereas the inclusion of inguinal regions still remains controversial because of the subsequent adverse side effects. Sentinel lymph node biopsies could clearly identify inguinal node-positive patients eligible for therapeutic groin irradiation. A sentinel lymph node navigation procedure is reported here to be a feasible and effective method for establishing the true inguinal node status in patients suffering from anal canal cancer. Based on the results of sentinel node biopsies, a selective approach could be proposed where node-positive patients could be selected for inguinal node irradiation while node-negative patients could take advantage of inguinal sparing irradiation, thus avoiding toxic side effects.

Comparison of pulsed photothermal radiometry, optical coherence tomography and ultrasound for melanoma thickness measurement in PDMS tissue phantoms

Melanoma accounts for 75% of all skin cancer deaths. Pulsed photothermal radiometry (PPTR), optical coherence tomography (OCT) and ultrasound (US) are non-invasive imaging techniques that may be used to measure melanoma thickness, thus, determining surgical margins. We constructed a series of PDMS tissue phantoms simulating melanomas of different thicknesses. PPTR, OCT and US measurements were recorded from PDMS tissue phantoms and results were compared in terms of axial imaging range, axial resolution and imaging time. A Monte Carlo simulation and three-dimensional heat transfer model was constructed to simulate PPTR measurement. Experimental results show that PPTR and US can provide a wide axial imaging range (75 μm-1.7 mm and 120-910 μm respectively) but poor axial resolution (75 and 120 μm respectively) in PDMS tissue phantoms, while OCT has the most superficial axial imaging range (14-450 μm) but highest axial resolution (14 μm). The Monte Carlo simulation and three-dimensional heat transfer model give good agreement with PPTR measurement. PPTR and US are suited to measure thicker melanoma lesions (>400 μm), while OCT is better to measure thin melanoma lesions (<400 μm).

Sentinel lymph node in carcinoma of the anal canal: a review

AIMS

To review the studies investigating the efficacy of the sentinel lymph node (SLN) procedure in anal canal carcinoma and to evaluate its potential role in guiding a more selective approach for patients with the malignancy.

METHODS

A literature search in the PubMed database was preformed using the key words "sentinel lymph node" and "anal cancer". All indexed original articles (except case reports) on the SLN procedure in cancer of the anal canal were analysed.

RESULTS

There are five published series to date. Eighty-four patients were studied. Rates of SLN detection and removal ranged from 66 to 100% of patients investigated. Nodal metastases were found in 7.1 to 42% of cases. No serious complications were reported.

CONCLUSIONS

The technique has proven to be safe and effective in sampling inguinal SLNs. The detection of occult metastases in clinically unsuspicious nodes represents an important improvement in the process of staging these patients, which has not been possible with any other method of diagnosis. Although SLN procedure is still in an early phase of investigation in this type of cancer, it emerges as an objective method to guide individual therapeutic decisions.

What is a sentinel node and what is a false-negative sentinel node?

Morton's original definition of a sentinel node as the first lymph node to receive afferent lymphatic drainage from a primary tumor reflects the concept of stepwise spread of cancer through the lymphatic system. Several new definitions have been developed, based on surgical anatomy and on the technique that is used to find the node. The various definitions of a sentinel node are critically analyzed. Breast cancer surgeons use three different definitions of a false-negative sentinel node biopsy. The best definition appears to be based on the assumption that the procedure is truly positive if either the sentinel node or a suspicious node that is not radioactive or blue contains metastatic disease.

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.

Melanoma in children and adolescents

Childhood and adolescent melanoma is rare, accounting for only 1.3% for all cases of cancer in patients under the age of 20 years. However, in 15-19 year olds, melanoma accounts for up to 7% of all cancers. Review of reported cases in this age group reveals that predisposing 'paediatric' conditions such as a giant congenital melanocytic naevi or xeroderma pigmentosum are rarely present. Furthermore, inactivating germ-line mutations of the gene CDKN2A have only been reported in 1.5% of cases of early onset melanoma. Epidemiological studies suggest that interactions between solar exposure, development of naevi, pigmentary traits, and a family history of melanoma are the main determinants of melanoma development during the first 20 years of life. As yet, there are no available staging or treatment strategies for this group of patients so treatment recommendations are based on the adult experience. To improve our understanding of the natural history of melanoma and to identify the most appropriate therapies for young patients with this disease, practising physicians are encouraged to enroll their patients, especially those with advanced stage disease, in cooperative group trials which incorporate newer staging systems and promising therapies.

Reassessing the role of lymphatic mapping and sentinel lymphadenectomy in the management of cutaneous malignant melanoma

Lymphatic mapping and sentinel lymphadenectomy was developed as a minimally invasive technique to provide regional lymph node staging information for patients at high risk for metastatic melanoma, but without clinically palpable disease. Only patients who demonstrate micrometastases undergo complete regional lymphadenectomy, sparing approximately 80% of patients the expense and morbidity of an elective lymph node dissection. This technique has been widely accepted as the preferred method to determine the pathologic status of the regional lymph nodes and the staging information gained is incorporated into the latest version of the American Joint Committee on Cancer staging system for cutaneous melanoma. Still, there is much controversy as to the use of this technique as a staging procedure and its overall therapeutic benefit in the treatment of patients with melanoma. Currently ongoing clinical trials will determine if lymphatic mapping and sentinel lymphadenectomy directly influences overall survival for patients with malignant melanoma. We review the latest technical aspects of this procedure and discuss the controversies surrounding its use.

Malignant melanoma

In the European Community cutaneous melanoma accounts for 1 and 1.8% of cancers occurring in men and women, respectively. The incidence rate is increasing faster than that of any other tumour. Sun exposure, patient's phenotype, family history, and history of a previous melanoma are the major risk factors. The change over a period of months is the main sign of a skin lesion turned into a melanoma. The ABCDE scheme for early detection of melanoma is commonly accepted. A new staging classification will be published in the next AJCC/UICC Cancer Staging System Manual in 2002. The clinical course of melanoma is determined by its dissemination and depends on thickness, ulceration, localisation, gender and histology of the primary tumour. Tumour stage at diagnosis remains the major prognostic factor. Surgery is the standard treatment option for operable local-regional disease. Sentinel node biopsy represents a promising experimental approach in the clinical detection and early treatment of occult lymph node involvement. For metastatic inoperable patients systemic chemotherapy can be attempted, while radiation therapy has to be considered as palliative treatment. No studies concerning frequency of follow-up are currently available, but common procedures may be performed.

Previous wide local excision of primary melanoma is not a contraindication for sentinel lymph node biopsy of the trunk and extremity

BACKGROUND AND OBJECTIVES

The role of sentinel lymph node biopsy (SLNB) in patients with a previous wide local excision (WLE) was examined with case-control methodology.

METHODS

A total of 168 consecutive cases of SLNB were performed in patients with truncal and extremity melanoma with tumor thickness of > or = 1 mm between October 1997 and June 2000 and were followed prospectively. For comparison, 65 of the 103 SLNB patients referred to us after their WLE (cases) were matched by tumor thickness to 65 patients who had SLNB with concurrent WLE (controls). Radiocolloid (technetium-99m sulfur colloid) was used in all cases; in addition, vital blue dye (patent blue) was used in the control group. The two groups were followed for a median of 15.4 months.

RESULTS

SLNs were identified in all patients with an average of 2.1 (cases) and 2.0 (controls) SLNs excised per patient (P = 0.77). Twenty one (32.3%) of those having SLNB after previous WLE (cases) and 23 (35.4%) of those with concurrent WLE and SLNB (controls) were found to have metastatic disease in the SLN. The only false-negative in this group was detected in clinical follow-up in a patient whose truncal WLE was previously closed with a rotation flap (case). There was no significant difference in relapse-free survival (P = 0.209) and overall survival (P = 0.692) between groups.

CONCLUSIONS

SLNB is feasible in patients with previous WLE for extremity and truncal melanoma. Similar rates of sentinel positivity are found when compared with those in whom their WLE was done concurrently.

Combined MR lymphangiography and MR imaging-guided needle localization of sentinel lymph nodes using Gadomer-17

OBJECTIVE

The goals of our study were to determine the technical feasibility of dynamic MR lymphangiography for detecting sentinel lymph nodes using Gadomer-17 contrast material to compare these results to the clinically standardized blue dye contrast agent, and to show MR imaging-guided needle localization marking of the sentinel nodes.

MATERIALS AND METHODS

Six anesthetized swine underwent MR imaging before and for 1 hr after interstitial injection of Gadomer-17 in the posterior tongue and intradermally in the stifle (knee). Using MR imaging guidance, we percutaneously placed a histology needle into the sentinel node or nodes. A standardized intraoperative sentinel node detection procedure was then performed using isosulfan blue contrast agent. Sentinel nodes identified on the MR images were compared with and matched to those identified by biopsy needle localization and the isosulfan blue contrast agent. RESULTS. Interstitial and intradermal injection of Gadomer-17 resulted in a lasting, increased MR signal in the regional lymph nodes. Seven sentinel nodes were identified in both the neck and the groin, with one pig showing two sentinel nodes in the neck and another showing two sentinel nodes in the groin. In all cases, the isosulfan blue contrast agent agreed with the location of the sentinel node determined by Gadomer-17 and marked with the needle.

CONCLUSION

In this large animal model, dynamic MR angiography of sentinel lymph nodes is technically feasible using a contrast agent (Gadomer-17) and can be easily combined with MR imaging-guided needle localization.

Interstitial MR lymphangiography for the detection of sentinel lymph nodes

BACKGROUND AND OBJECTIVES

The challenge for implementation of sentinel lymph node biopsy is to develop a reliable minimally invasive technique that identifies all possible sentinel nodes with high temporal and spatial resolution. This study evaluated the use of a magnetic resonance imaging (MRI) contrast agent (USPIO) for preoperative sentinel node detection.

METHODS

Anesthetized pigs received interstitial or intradermal injections of ultra small superparamagnetic of iron oxide (USPIO) (0.2 or 5 mg Fe) in the L/R posterior tongue and stifles (knee) respectively. MRI was done before, during injection and at 0.25, 0.5, 1, 2, 4, 6, 24, and 48 hr after which isosulfan blue sentinel node mapping was done.

RESULTS

In the tongue, both doses of USPIO identified the sentinel node in the early images. No additional nodes were detected by MR at 24 or 48 hr. In the hind limb, sentinel nodes identified on the early MR images were also identified by the isosulfan blue. In both locations, the higher dose also identified secondary nodes some of which were also identified by the isosulfan blue. All sentinel nodes that were identified by USPIO on MRI were noted to be stained brown at the time of dissection.

CONCLUSIONS

Interstitial MR lymphangiography is a useful technique for the detection of sentinel lymph nodes. This method provides excellent simultaneous temporal and spatial resolution, is minimally invasive, and can be performed preoperatively.

No indication for performing sentinel node biopsy in melanoma patients with a Breslow thickness of less than 0.9 mm

In thin melanomas, the involvement of regional nodes is very uncommon. Recent sentinel node (SN) studies have confirmed the absence of positive regional lymph nodes in melanomas < 0.76 mm and a 5% positivity in melanomas between 1.0 and 1.99 mm. The chance of regional lymph node involvement - and therefore whether it is relevant to perform the SN procedure - seems to depend on the Breslow thickness of the primary tumour. However, a Breslow thickness cut-off point has not yet been established. We evaluated a melanoma population that had undergone an SN procedure to determine this point, so that the procedure can be restricted to a smaller group of patients in future. In a total of 348 patients with proven American Joint Committee on Cancer (AJCC) stages I or II cutaneous melanoma with a Breslow thickness > or = 0.5 mm the triple technique was used, consisting of preoperative visualization of the lymph channels from the initial site of the melanoma towards the SN by (dynamic) lymphoscintigraphy, intraoperative visualization of those particular lymph channels and nodes with blue dye, and a gamma probe to measure accumulated radioactivity in radiolabelled lymph nodes. In melanomas thinner than 0.90 mm, no positive SN was found (95% confidence interval 0-5%). This group consisted of 75 patients (22%), with a median follow-up of 31 months. Our data suggest that this procedure need no longer be indicated for almost a quarter of the patient population, because the cut-off point for nodal involvement appears to be a Breslow thickness of 0.90 mm.