Current surgical guidelines for melanoma recommend wide excision of the primary tumor along with sentinel lymph node (SLN) biopsy for tumors 1 mm in thickness or greater, with complete node dissection for those patients with a positive node or nodes. The role of SLN in patients with thinner tumors (<1 mm) remains an area of debate; currently most guidelines suggest SLN for selected patients, but the criteria for identifying patients with thin melanoma at sufficient risk to justify the procedure have not been agreed upon. Also highly controversial is the value of routine complete node dissection after the removal of a microscopically positive sentinel node, especially when the node contains only very small tumor deposits (again with no agreed upon definition).
The role of SLN biopsy was explored by the MSLT-I prospective trial, which randomized patients to wide excision and SLN biopsy or to wide excision and observation. SLN biopsy was found to be a strong predictor of the risk of recurrence (5-year disease-free survival was 83% in node negative patients versus 53% in node positive patients; HR 3.04) and death (5-year melanoma-specific survival 90% in node negative patients versus 73% in node positive patients; HR 2.48). Moreover, SLN biopsy also increased relapse-free survival; after a median of 60 months, 27% of patients in the observation arm had relapsed versus 21% in the SLN biopsy arm. However there was no discernable benefit on survival. In updated results, it was also apparent that SLN biopsy identified patients who, in time, required complete node dissection, and that SLN biopsy may increase survival in the subset of node-positive patients.
Several studies have indicated that SLN status predicts prognosis in patients with thick melanomas, however the data regarding the role of SLN in patients with thinner melanomas is less clear. In our experience, few patients with melanomas of Breslow thickness <0.76 mm have positive nodes, however those with melanomas of 0.76–1.0 mm have a sufficient risk of nodal involvement to justify consideration of SLN biopsy. Ideally, additional clinicopathologic indicators of risk should be considered when making decisions regarding SLN biopsy. For example, younger age has been shown to correlate with increased risk of nodal involvement. In addition, in those patients with melanomas greater than 0.5 mm, mitotic rate has been shown to be related to prognosis and can also help identify those patients in whom SLN biopsy may be helpful. The MSLT-II trial is assessing whether PCR can detect positive metastases in the SLN, and whether complete lymph node dissection can be avoided in some patients with positive sentinel nodes.
This presentation will review the lessons learned from these and other clinical trials of sentinel node biopsy and discuss current recommendations for the use of sentinel node biopsy and completion node dissection.