EORTC Melanoma Group sentinel node protocol identifies high rate of submicrometastases according to Rotterdam Criteria

Abstract

Sentinel node (SN) status is the most important prognostic factor for disease-free survival (DFS) and overall survival (OS) in stages I–II melanoma. We evaluated the positive sentinel node identification rate of the EORTC Melanoma Group (MG) protocol as well as its capacity to identify minimal tumour burden, according to the Rotterdam Criteria in 421 consecutive patients. Correlations between primary tumour characteristics and SN tumour burden were investigated. The same 2 pathologists worked up all SNs according to the EORTC MG protocol and tumour burden was scored according to the Rotterdam Criteria (<0.1 mm, 0.1–1.0 mm and >1.0 mm for the largest diameter of the largest metastasis in the SN). The positive SN detection rate was 28.7% with a false negative rate of 10.4% at a median Breslow thickness of 2.1 mm. The high positive identification rate of about 30% of the EORTC MG protocol has been confirmed in this study. The protocol is sensitive and identifies submicrometastases (<0.1 mm) in a high percentage (18%). The variables SN tumour load, non-SN (NSN) status and ulceration of the primary were independent prognostic factors for DFS and OS in the multivariate analysis. At a median follow-up time of 4.3 years patients with minimal tumour burden (<0.1 mm) had a 5 year OS rate of 91%, virtually identical to 90% for SN-negative patients. The NSN positivity rate of 0% in these patients indicates that they may be spared a completion lymph node dissection (CLND) and its morbidity.