32. Sentinel lymph node biopsy in patients with thin melanoma

Abstract

Background Most new cases of melanoma are thin (≤1 mm) tumours. A small but significant proportion of patients with thin melanoma suffer disease progression and melanoma-related death. We sought to determine clinico-pathological factors predictive poor clinical outcomes in patients with thin melanoma who underwent sentinel lymph node (SLN) biopsy. Methods Patients diagnosed with a single primary thin cutaneous melanoma who underwent SLN biopsy between 1992 and 2009 were identified from the database of the Melanoma Institute Australia. Thin melanomas were defined as having a Breslow thickness ≤1.00 mm. Clinico-pathological factors associated with SLN positivity, regional lymph node recurrence and survival were analysed. Results There were 432 patients (226 male, 206 female, median age 49.5 years). SLNs were positive in 29 (6.7%) patients. No SLN positivity was detected in 37 patients with tumour thickness ≤0.50 mm. Breslow thickness (OR = 52.0, 95%CI 1.4-1948.7) and presence of lymphovascular invasion (OR = 8.5, 95%CI 1.8-41.4) were the only independent predictors of SLN positivity. Anatomic location in head/neck region (OR = 8.5, 95%CI 1.8-40.2; compared to location in the limbs) was the only independent predictor of regional lymph node recurrence. Mitotic rate was the only independent predictor of melanoma-specific survival (HR=1.2, 95% CI 1.1-1.3). SLN positivity in Clark level III tumours (HR=8.0, 95%CI 1.8-36.0) and anatomic location in head/neck region in Clark level IV tumours (HR = 23.7, 95% CI 2.0-277, compared to limbs) were the only independent predictors of poorer disease-free survival. Conclusions Patients with thicker tumours (>0.5 mm) and other adverse prognostic factors (e.g., ulceration, elevated mitotic rate, lymphovascular invasion) have a greater risk of occult nodal metastasis and are more likely to benefit from SLN biopsy.