Age and Lymphovascular Invasion Accurately Predict Sentinel Lymph Node Metastasis in T2 Melanoma Patients.

ABSTRACT

BACKGROUND: The risk of sentinel lymph node (SLN) metastasis in melanoma is related directly to tumor thickness and inversely to age. The authors hypothesized that for T2 (thickness 1.1-2.0 mm) melanoma, age, and other factors may be able to identify a cohort of patients with a low risk of SLN metastases. METHODS: The authors developed logistic regression models to predict positive SLNs in patients undergoing SLN biopsy for T2 melanoma using the National Cancer Database. Classification and regression-tree analysis were used to identify groups of patients with high and low risk for SLN metastases. The prediction model then was applied to a separate data set from a multicenter randomized clinical trial. RESULTS: The study identified 12,918 patients with T2 melanoma undergoing SLN biopsy with clinically node-negative melanoma. In the multivariable analysis, increasing thickness, younger age, lymphovascular invasion (LVI), mitotic rate of 1/mm2 or more, axial location, and Clark level of 4 or 5 were independent risk factors for SLN metastases. A cohort based on age (> 56 years) and no LVI was identified with a relatively low risk (7.8%; 95% confidence interval 7.2-8.4%) of SLN metastases. The independent data set of 1531 patients with T2 melanoma confirmed these findings. Among elderly patients (age > 75 years) with melanoma 1.2 mm or smaller and no LVI, the risk of a positive SLN was 4.9% (95% confidence interval 3.3-7.1%). CONCLUSIONS: Younger age and LVI are powerful predictors of SLN metastases for patients with T2 melanoma. This prediction model can inform shared decision-making regarding whether to perform SLN biopsy for older patients with otherwise low-risk T2 melanoma.