The importance of adequate primary tumor excision margins and sentinel node biopsy in achieving optimal locoregional control for patients with thick primary melanomas.

OBJECTIVE: This study sought to investigate the impact of histopathologically measured excision margins and SNB on local and locoregional disease control in patients with primary cutaneous melanomas more than 4 mm thick.

BACKGROUND: Most current guidelines recommend at least a 2-cm surgical margin (which corresponds to a 16-mm histopathologic margin). These guidelines are based on limited evidence, mostly obtained in patients who did not have an SNB.

METHODS: Histopathologic tumor excision margins for clinically lymph node-negative patients with melanomas more than 4 mm thick, treated at Melanoma Institute Australia (1992-2009), were determined. Clinicopathologic predictors of local and locoregional disease-free survival were investigated.

RESULTS: There were 632 patients eligible for the study; of these, 397 (62.8%) had an SNB. The median histopathologic excision margin was 15 mm (interquartile range, 11.0-19.5 mm). After a median follow-up of 37 months, local and locoregional recurrences were observed in 48 (7.6%) and 159 (25.2%) patients, respectively. Excision margin as a continuous variable was a significant predictor of local [hazard ratio (HR), 0.91; P < 0.001) and locoregional (HR, 0.97; P = 0.042) tumor control on multivariate analyses. Patients with histopathologic margins 16 mm or less had worse local disease-free survival (HR, 2.41; P = 0.01). Patients who did not have an SNB were at higher risk of locoregional recurrence (HR, 1.67; P = 0.003).

CONCLUSIONS: Histopathologically determined primary tumor excision margins more than 16 mm, corresponding to 2-cm surgical margins, were associated with better local control in patients with melanomas more than 4 mm thick. Patients achieved the best local and locoregional control when SNB was coupled with a more than 16-mm histologic excision margin.