Hot or not? The 10% rule in sentinel lymph node biopsy for malignant melanoma revisited

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.

Redefining Criteria to Ensure Adequate Sentinel Lymph Node Biopsy With Dual Tracer for Breast Cancer

Background

For sentinel lymph node biopsy (SLNB) in patients with breast cancer, the dual tracer of blue dye and radioisotope with the 10% rule that all nodes with radioactive count of 10% or more of the hottest node ex vivo should be removed is widely accepted. However, the cut-off point of radioactivity is being questioned for possibly excessive removal of negative nodes.

Methods

To compare different percentile rules and optimize the criteria for identifying SLNs, we established a database which prospectively collected the radioactivity, status of blue dye and the pathological results of each SLN in breast cancer patients who successfully underwent SLNB with a combination of methylene blue and radioisotope.

Results

A total of 2,529 SLNs from 1,039 patients were identified from August 2010 to August 2019. 16.4% (414/2,529) positive nodes were removed at a cost of 83.6% (2115/2,529) negative nodes removed excessively. Up to 17.9% (375/2,115) negative nodes were removed as radioactively hot nodes without blue staining. By gradually increasing the threshold by each 10%, the number of negative nodes identified reduced by 18.2% (385/2,115) with only three node-positive patients (1.0%) missed to be identified using the “40% + blue” rule. In patients with ≥ 2 SLNs removed, 12.3% (238/1,942) negative nodes avoided unnecessary removal with only 0.8% (2/239) positive patients missed with the “hottest two + blue” rule.

Conclusions

Our data indicated that the “40% + blue” rule or the “hottest two + blue” rule for SLNB with the dual tracer of blue dye and radioisotope may be considered as a potential alternative rule to minimize extra nodes resected. Nonetheless, it should be validated by prospective trials with long-term follow-up.

Evaluation of camera-based freehand SPECT in preoperative sentinel lymph node mapping for melanoma patients

BACKGROUND

Assessment of lymphatic status via sentinel lymph node (SLN) biopsy is an integral and crucial part of melanoma surgical oncology. The most common technique for sentinel node mapping is preoperative planar scintigraphy of an injected gamma-emitting lymphatic tracer followed by intraoperative node localization using a non-imaging gamma probe with auditory feedback. In recent years, intraoperative visualization of SLNs in 3D has become possible by coupling the probe to an external system capable of tracking its location and orientation as it is read out, thereby enabling computation of the 3D distribution of the tracer (freehand SPECT). In this project, the non-imaging probe of the fhSPECT system was replaced by a unique handheld gamma camera containing an array of sodium iodide crystals optically coupled to an array of silicon photomultipliers (SiPMs). A feasibility study was performed in which preoperative SLN mapping was performed using camera fhSPECT and the number of detected nodes was compared to that visualized by lymphoscintigraphy, probe fhSPECT, and to the number ultimately excised under non-imaging probe guidance.

RESULTS

Among five subjects, SLNs were detected in nine lymphatic basins, with one to five SLNs detected per basin. A basin-by-basin comparison showed that the number of SLNs detected using camera fhSPECT exceeded that using lymphoscintigraphy and probe fhSPECT in seven of nine basins and five of five basins, respectively. (Probe fhSPECT scans were not performed for four basins.) It exceeded the number excised under non-imaging probe guidance for seven of nine basins and equaled the number excised for the other two basins.

CONCLUSIONS

Freehand SPECT using a prototype SiPM-based gamma camera demonstrates high sensitivity for detection of SLNs in a preoperative setting. Camera fhSPECT is a potential means for efficiently obtaining real-time 3D activity distribution maps in applications such as image-guided percutaneous biopsy, and surgical SLN biopsy or radioguided tumor excision.

Surgical Management of Lymph Nodes in Melanoma

This article provides a comprehensive evaluation of surgical management of the lymph node basin in melanoma, with historical, anatomic, and evidence-based recommendations for practice.

Sentinel lymph node biopsy in melanoma: Which hot nodes should be harvested and is blue dye really necessary?

OBJECTIVES

The '10% rule' has become widely accepted by surgeons performing sentinel lymph node biopsy (SLNB) for melanoma. The purpose of this study was to compare the '10% rule' with alternative node harvesting criteria. In particular, we were interested to see whether the use of blue dye had any impact on the sensitivity of the test and whether it is necessary to remove all hot nodes.

METHODS

We reviewed 537 SLNBs performed for primary melanoma from 2009-2015. SLNB was offered to all patients with 1-4 mm Breslow thickness melanoma and sentinel nodes were harvested according to the '10% rule'.

RESULTS

One hundred sixteen patients (22%) had at least one positive sentinel node and there were 45 positive nodal basins from which more than one sentinel node had been harvested. Excluding blue dye and sampling only hot nodes would have enabled a 5% reduction in nodes harvested, without any compromise in the sensitivity of the test. However, applying harvesting criteria whereby not all hot nodes are taken was associated with a loss of sensitivity, with positive sentinel nodes being missed and patients understaged.

CONCLUSIONS

Our data do not support the continued use of blue dye in SLNB for melanoma, as it does not improve the sensitivity of the test. This series adds to growing evidence, suggesting that the '10% rule' with the inclusion of blue nodes should be reconsidered and that radiocolloid tracer alone is sufficient for sentinel node localisation.

Is the non-sentinel lymph node compartment the next site for melanoma progression from the sentinel lymph node compartment in the regional nodal basin?

Melanoma patients with additional positive lymph nodes in the completion lymph node dissection (CLND) following a positive sentinel lymph node (SLN) biopsy would have a poorer prognosis than patients with no additional positive lymph nodes. We hypothesize that the progression of disease from the SLN to the non-SLN compartment is orderly and is associated with the worsening of the disease status. Thus, the SLN and non-SLN compartments are biologically different in that cancer cells, in general, arrive in the SLN compartment before spreading to the non-SLN compartment. To validate this concept, we used a large cohort of melanoma patients from our prospective SLN database in an academic tertiary medical center. Adult cutaneous melanoma patients (n = 291) undergoing CLND after a positive SLN biopsy from 1994 to 2009 were analyzed. Comparison of 5-year disease-free survival and 5-year overall survival between positive (n = 66) and negative (n = 225) CLND groups was made. The 5-year disease-free survival rates were 55% (95% CI 49-62%) for patients with no additional LN on CLND versus 14% (95% CI 8-26%) in patients with positive LN on CLND (p < 0.0001, log-rank test). The median disease-free survival time was 7.4 years with negative CLND (95% CI 4.4-15+ years) and 1.2 years with positive CLND (95% CI 1.0-1.8 years). The 5-year overall survival rates were 67% (95% CI 61-74%) for negative CLND versus 38% (95% CI 28-52%) for positive CLND (p < 0.0001, log-rank test). The median overall survival time was 12.1 years for negative CLND (95% CI 9.3-15+ years) and 2.5 years for positive CLND (95% CI 2.2-5.7 years). This study shows that CLND status is a significant prognostic factor for patients with positive SLNs undergoing CLND. Also, it suggests an orderly progression of metastasis from the SLN to the non-SLN compartment. Thus, the SLN in the regional nodal basin draining the primary melanoma may serve as an important gateway for metastasis to the non-SLN compartment and beyond to the systemic sites.