E307: Defining the Sentinel Lymph Node in Melanoma: Is the Hottest Node Always the Node with Metastases

ePoster Abstract Author(s)

Udai S. Sibia, MD MBA

Donald L. Morton Complex General Surgical Oncology Fellow
Saint John's Cancer Institute, Providence Health System
Santa Monica, California, United States

Submitter(s)

Udai S. Sibia, MD MBA

Donald L. Morton Complex General Surgical Oncology Fellow
Saint John's Cancer Institute, Providence Health System
Santa Monica, California, United States

Author(s)

Udai S. Sibia, MD MBA

Donald L. Morton Complex General Surgical Oncology Fellow
Saint John's Cancer Institute, Providence Health System
Santa Monica, California, United States
KJ

Katherine M. Jackson, MD

Donald L. Morton Complex General Surgical Oncology Fellow
Saint John's Cancer Institute, Providence Health System, United States
SS

Stacey L. Stern, MS

Manager Data Management
Saint John's Cancer Insitute, Providence Health System, United States
KL

Kristel A. Lourdault, PhD DVM (she/her/hers)

Senior Clinical Research Scientist
Saint John's Cancer Institute, Providence Health System
Santa Monica, California, United States
LF

Leland Foshag, MD

Program Director - Complex General Surgical Oncology Fellowship
Saint John's Cancer Institute, Providence Health System, United States
RE

Richard Essner, MD (he/him/his)

Co-Director of Melanoma Research Program
Saint John's Cancer Institute, Providence Health System
Santa Monica, California, United States

Introduction:

Sentinel lymph node (SLN) biopsy was devised as a staging tool in melanoma. Originally defined by the presence of blue staining in the regional lymph node basin, the procedure has evolved using the combination of blue dye and radiocolloid for node identification with a hand-held gamma probe. Yet, there is no consensus on the definition of a radioactive SLN. It is suggested that all lymph nodes that have counts >10% of the most radioactive (hottest) node be treated as SLNs. This definition has not been validated.

Methods:

Our prospectively collected melanoma database was queried for patients with primary cutaneous melanoma with tumor-positive (+) SLNs. All patients underwent pre-operative lymphoscintigraphy and intraoperative gamma probe detection. Radioactive tracer counts for all lymph nodes removed were compared to the hottest node and post-resection lymph node basins. Descriptive statistics were used for analysis.

Results:

We identified 134 melanoma patients with +SLN. Median age was 59 years, median Breslow thickness was 2.3 mm (range 0.4-11.5 mm) and 40% of primary tumors were ulcerated. The primary tumor sites were extremity (44%), trunk (40%), or head & neck (16%), and they drained to 143 lymph node basins: axilla (53%), groin (26%), and neck (21%). A median of 2 SLNs (range 1-5) were excised per patient, and a median of 1 had +SLN (range 1-5). Seventy patients (52.5%) underwent completion lymph node dissection, of whom 15 (21%) were found to have a median of 2 additional nodal metastasis (range 1-13).

The hottest SLN identified was positive for metastasis in 123 (92%) patients. The +SLN was identified within a median 78% of radioactive counts (range 21%-94%) of the hottest node. Upon sub-analysis, the +SLN was the most radioactive in 96% of axilla, 95% of groin, and 80% of neck lymph node basins. Removal of SLNs with 70% or higher radioactive counts of the hottest node identified all +SLNs from the axilla and groin lymph node basins. Removal of SLNs with 25% or higher radioactive counts of the hottest node identified all +SLNs from the neck lymph node basin. Radioactive counts were not predictive of lymph node metastasis in CLND.

Conclusions:

The SLN with the highest radioactive counts is most commonly the site of metastasis in melanoma. The recommendation for removing all SLNs can be increased to 70% or higher than the ex-vivo radioactive count of the hottest SLN from the axilla and groin lymph node basins, and it can be increased to 25% or higher of the hottest SLN from the neck lymph node basin. This is becoming especially important in the modern era of melanoma treatment where SLN biopsy is only a staging procedure.

Learning Objectives:

Upon completion, participants will be able to describe the use of radiocolloid for sentinel lymph node identification in cutaneous melanoma.
Upon completion, participants will be able to describe the association between tumor-positive sentinel lymph nodes and radioactivity of the lymph node basin using radiocolloid for sentinel lymph node identification.
Upon completion, participants will be able to describe the differences in radiocolloid use for sentinel lymph node identification in axillary, groin, and neck lymph node basins.