25. Sentinel Lymph Node Positivity in Cutaneous Melanoma and its Correlation to a 31 Gene-expression Profile Test and Two Lymph Node Risk Calculators

Abstract

PURPOSE: Sentinel lymph node biopsy (SLNB) provides prognostic information and a therapeutic benefit for patients with melanoma. It is discussed at stage pT1b and is recommended for stage pT2a or higher.1 This study compared the use of available sentinel lymph node positivity risk calculators and a 31-gene expression profile test (DecisionDx) in melanoma patients undergoing SLNB. METHODS: Retrospective data of a tertiary care facility from 01/2016 to 12/2021 was analyzed of patients with melanoma that underwent a SLNB and had DecisionDx. The Melanoma Institute of Australia (MIA) and Memorial Sloan Kettering (MSK) online risk calculators were used to predict SLN positivity pre-operatively. Descriptive statistics were used to summarize major trends. Univariate statistics were used to compare subgroups. RESULTS: Two hundred and fifty-two (n=252) patients met inclusion criteria. Positive sentinel lymph nodes were identified in 12 (4.8%) patients. MSK median risk score was 10% [6%, 18%]. MIA median risk score was 12% [7%, 21%]. DecisionDx classified patients into four risk groups distributed as follows: 98 (38.9%) IA, 50 (19.8%) IB, 39 (15.5%) IIA, 65 (25.8%) IIB. Of the patients that had a positive SLNB, there was a relatively even distribution between DecisionDx classes: 3 (25%) IA, 2 (16.7%) IB, 4 (33.3%) IIA, 3 (25%) IIB. CONCLUSION: Our results indicated similar SLNB positivity rates in low- and high-risk DecisionDx profiles to existing literature.2 Most patients had similar MIA and MSK values. While a correlation between SLNB positivity and DecisionDx stage wasn’t seen, important prognostic information was still gained from obtaining the test.