Prediction of Residual Nodal Disease at Completion Dissection Following Positive Sentinel Lymph Node Biopsy for Melanoma

Introduction: While recent trial data have demonstrated no survival benefit to immediate completion lymph node dissection (CLND) for positive sentinel lymph node (SLN) disease in melanoma, prediction of non-SLN disease may help risk-stratify patients for more intensive observation of the nodal basin. Patients and Methods: A retrospective cohort of patients with positive SLN biopsy (SLNB) who underwent CLND was identified (1996–2016). A risk score for likelihood of CLND-positive disease was developed based on factors associated with presence of CLND metastases identified on logistic regression. Survival outcomes were analyzed. Results: Among 312 patients with positive SLN, 192 underwent CLND and had complete pathologic data for evaluation. The median age of the study cohort was 53 years [interquartile range (IQR) 43–66 years], and 112 (58%) were male. Thirty-one (16%) had non-SLN metastatic disease on CLND. The four factors independently associated with CLND positivity and thus included in the risk score were Breslow thickness ≥ 3 mm [odds ratio (OR) 2.56, p = 0.047], presence of primary tumor-infiltrating lymphocytes (OR 0.33, p = 0.013), ≥ 2/3 positive-to-total SLN ratio (OR 4.35, p = 0.003), and combined subcapsular and parenchymal metastatic SLN location or metastatic deposit ≥ 1 mm (OR 4.45, p = 0.013). The four-point risk score predicted CLND positivity well with area under the curve of 0.82 (0.80–0.85). Increasing risk score was independently associated with increasingly worse melanoma-specific survival [hazard ratio (HR) = 1.54, p = 0.001]. Conclusions: Likelihood of residual nodal disease after positive SLNB and survival can be predicted from primary tumor and SLN characteristics. High-risk patients may warrant more intensive surveillance of the nodal basin to reduce risk of loss of regional control.