Abstract
Sentinel lymph node biopsy (SLNB) is a standard procedure for initial management in intermediate thickness and thick melanomas. Clinical trials such as MSLT-I, MSLT-II, and DeCOG-SLT have shown that SLNB provides staging information that significantly impacts prognosis and is independent of other variables. However, the use of SLNB for thin melanomas has not been addressed in these trials. In this study, we investigated whether SLN status is prognostic in patients with thin melanoma (Breslow thickness ≤1mm) using an institutional series of consecutive cutaneous melanoma patients who underwent SLNB within 90 days of their diagnostic skin biopsy (2004-2018). Of the 854 patients in the cohort, 196 had thin melanoma and were included in the study, with a median follow-up of 7.1 years. SLNB was positive in 20 patients (10.2%). 19/196 patients experienced a relapse at any site, with 7 locally or in-transit, 5 in the nodal basin, and 7 at a distant site. Patients who underwent SLNB and were SLN positive had a worse 5-year relapse-free (80.0% vs. 93.2%, p=0.05) and distant metastasis-free survival (86.7% vs. 97.3%, p=0.03). We conclude that thin melanoma patients are at significant risk of SLN metastases, and that SLN status is a valuable prognostic test for patients treated at our institution, consistent with reports from other academic centers. However, the prognostic value must be weighed against costs that extend beyond the perioperative period. Prospectively validated gene expression-based tests, such as CP-GEP, are likely to assist clinicians in selecting thin melanoma patients for SLNB in the future.