Predictors of Sentinel Lymph Node Metastasis in Very Thin Invasive Melanomas.

Abstract

Melanomas <0.8 mm in Breslow depth have less than 5% risk for nodal positivity. Nonetheless, nodal positivity is prognostic for this group. Early identification of nodal positivity may improve outcomes for these patients. To determine the degree to which ulceration and other high-risk features predict sentinel lymph node (SLN) positivity for very thin melanomas. The National Cancer Database was reviewed from 2012 to 2018 for melanoma patients with Breslow thickness < 0.8 mm. Data were analyzed between July 7, 2022, through February 25, 2023. Patients were excluded if data regarding their ulceration status or sentinel lymph node biopsy (SLNB) performance were unknown. We analyzed patient, tumor, and health system factors for their effect on SLN positivity. Data were analyzed using chi-square tests and logistic regressions. Overall survival (OS) was compared by Kaplan-Meier analyses. Positive nodal metastases were seen in 876 (5.0%) of patients who underwent sentinel lymph node biopsy (17,692). Factors significantly associated with nodal positivity on multivariable analysis include: lymphovascular invasion (Odds ratio (OR)= 4.5, p< 0.001), ulceration (OR= 2.6, p < 0.001), mitoses (OR= 2.1, p< 0.001), and nodular subtype (OR= 2.1, p< 0.001). Five-year overall survival was 75% and 92% for patients with positive and negative SLN, respectively. Nodal positivity has prognostic significance for very thin melanomas. In our cohort, the rate of nodal positivity was 5% overall in these patients who underwent SLNB. Specific tumor factors (e.g. lymphovascular invasion, ulceration, mitoses, nodular subtype) were associated with higher rates of SLN metastases and should be used to guide clinicians in choosing which patients will benefit from sentinel lymph node biopsy.