Melanoma-specific survival in patients with positive sentinel lymph nodes: Relevance of sentinel tumor burden.

Background: The tumor burden within the sentinel lymph node (SLN) is not included in the 8th edition of the American Joint Committee of Cancer (AJCC) melanoma classification. Therefore, we analysed the prognostic relevance of the SLN tumor burden in the stage III subgroups.
Patients and Methods: A total of 736 patients with melanoma with positive SLN and long-term follow-up (mean, 64.4 months; median, 59.0 months) were assessed. SLN tumor burden was evaluated by the maximum diameter of the largest deposit in all patients.
Results: By univariate Kaplan-Meier analyses, melanoma-specific survival (MSS) of patients in stage IIIA, IIIB and IIIC and lower sentinel tumor burden (cut-offs ≤0.5 mm and ≤1 mm) was significantly better than that in patients with higher sentinel tumor load (>0.5 mm and >1 mm). By multivariate analysis using the Cox model, the maximum diameter of the largest deposit (cut-off ≤0.5 mm versus >0.5 mm and cut-off ≤1 mm as continuous variables) represented an independent prognostic parameter for MSS in stage III patients. Cut-off of 0.5 mm showed a slightly higher area under the receiver operating characteristic curve (AUC = 0.617) when than the cut-off of 1 mm (AUC = 0.599).
Conclusion: The prognosis of patients with stage III melanoma can be determined more precisely if the SLN tumor burden is considered, also within the existing AJCC subgroups. Thus, this parameter should be included in future classifications, and our study provides benchmarks in estimating prognosis and counselling patients with melanoma with positive sentinel nodes beyond the 8th AJCC Cancer Staging Manual. The optimal cut-off remains for SLN tumor burden remains to be determined, but our results suggest that a cut-off lower than 1 mm is preferable.
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