Survival Outcomes Following Lymph Node Biopsy in Thin Melanoma—A Propensity-Matched Analysis

The use of sentinel lymph node biopsy in patients with T1 melanoma ≤ 1 mm has not been reported in a prospective clinical trial setting, so these clinical outcomes remain understudied. This study seeks to evaluate overall survival (OS) with and without lymph node biopsy (LNB) in patients with clinical T1N0M0 melanoma (0.5–1.0 mm). Patients were identified using the National Cancer Data Base (2004–2012). After stratification into 0.5–0.7-mm and 0.8–1.0-mm groups, patients undergoing LNB were propensity score-matched 1:1 to patients not undergoing LNB. OS was compared using the Kaplan–Meier method and the stratified log-rank test. Resection was performed in 28,846 patients, and LNB in 14,028 (49%); 15,194 were included in propensity score-matched analysis. The LNB and no-LNB groups were well balanced on all studied covariates (standardized mean difference < 0.10). Among patients with tumors 0.5–0.7 mm, 5- and 10-year OS were 94.7% and 82.7%, respectively, for the LNB group compared with 94.3% and 84.4% for the no-LNB group (p = 0.35). Among patients with tumors 0.8–1.0 mm in thickness, 5- and 10-year OS were 93.9% and 81.6%, respectively, for the LNB group compared with 90.3% and 74.3% for the no-LNB group (p < 0.0001). There was no difference in OS by LNB status in patients with lesions 0.5–0.7 mm, consistently with recommendations against its routine use in this group. In lesions 0.8–1.0 mm, receipt of LNB was associated with a clinically small but significant improvement in OS. Further study is warranted to better understand this outcome difference.