Risk factors and patterns of recurrence after sentinel lymph node biopsy for thin melanoma.

While having a thin melanoma (defined as AJCC 8 T1 stage tumor ≤ 1.0 mm) with negative sentinel lymph node biopsy (SLNB) provides an excellent prognosis, some patients still develop recurrence and die. To determine risk factors for any recurrence (local/in-transit, nodal, distant) in thin melanoma patients with negative SLNB and assess survival outcomes. Retrospective review of thin melanomas with negative SLNB from 1999 to 2018 was performed. Two hundred and nine patients were identified. Clinicopathologic characteristics of the primary melanoma were collected. Patterns of recurrence for local/in-transit, nodal or distant recurrence and survival outcomes were analyzed. Eighteen patients (8.6%) developed recurrence: 3 (1.9%) local/in-transit, 4 (2.9%) regional/nodal, and 11 (5.3%) distant recurrence during a median follow-up time of 62 months. A multivariate Cox regression model showed that head and neck site (HR 3.52), ulceration (HR 10.8), and mitotic rate (HR 1.39) were significant risk factors for recurrence. Median time to first recurrence was 49 months. Patients with recurrence had a significantly worse 5 year overall survival than those without recurrence (82.2 vs 99.2%). A retrospective single center study and limited sample size. Did not factor in possible false negative SLNBs when calculating hazard ratios. For thin melanoma patients with negative SLNB, heightened surveillance is warranted for those with ulceration, primary tumor location on the head or neck, and elevated mitotic rate.