Utility of sentinel lymph node biopsy for acral lentiginous melanoma

Summary: Abstract Body: Guidelines on surgical management of clinically localized acral lentiginous melanoma (ALM), including recommendation for sentinel lymph node biopsy (SLNB), are extrapolated from studies with minimal representation of ALM in their cohorts. Additionally, overall survival (OS) outcomes from SLNB-based clinical decision-making are lacking. We sought to understand the relationship between undergoing SLNB and OS in patients with ALM. In this retrospective national cohort study, the National Cancer Database was queried for patients with ALM who met clinical criteria for SLNB (i.e. ≥0.8 mm thick or ulcerated tumors) between 2016 and 2021. The primary outcome was 3-year OS. Of 2409 eligible ALM patients, 1849 (77%) underwent SLNB. On multivariable logistic regression, patients undergoing SLNB were more likely to be younger (adjusted odds ratio [aOR]: 1.05, p < 0.01), male (aOR: 1.37, p < 0.01), and have ulcerated tumors (aOR: 1.9, p < 0.01). On Kaplan-Meier analysis of the overall cohort, patients who underwent SLNB had a 3-year OS rate of 86% vs. 82% for those who did not undergo SLNB (p = 0.05). On propensity-matched (PM) analysis, 3-year OS was 86% for the SLNB cohort vs. 85% for non-SLNB (p = 0.68). However, on subgroup analysis, PM clinical stage II patients who underwent SLNB had significantly improved 3-year OS (78% vs. 64%, p = 0.02). 3-year OS was significantly lower for SLN-positive patients compared to SLN-negative in both the overall (75% vs. 91%, p < 0.01) and PM cohorts (75% vs. 90%, p = 0.02). SLNB was not associated with improved OS in the overall cohort of ALM patients, though an OS advantage for patients with clinical stage II disease was found. Additionally, SLN-positivity was associated with worse OS, reaffirming the value of SLNB as a prognostication tool for ALM. Mohammad S. Farooq¹, Neha Shafique¹, Gracia M. Vargas¹, Alexander H. Varey^{2, 3, 4}, Serigne Lo^{3, 4}, Emily Y. Chu⁵, Michael E. Ming⁵, John T. Miura¹, Giorgos C. Karakousis¹ 1. Surgery, University of Pennsylvania, Philadelphia, PA, United States. 2. Surgery, Westmead Hospital, Westmead, NSW, Australia. 3. The University of Sydney Faculty of Medicine and Health, Sydney, NSW, Australia. 4. Melanoma Institute Australia, Sydney, NSW, Australia. 5. Dermatology, University of Pennsylvania, Philadelphia, PA, United States. Clinical Research: Epidemiology and Observational Research