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INDICATIONS FOR LYMPHADENECTOMY
INDICATIONS FOR LYMPHADENECTOMY
Prognosis for patients with regional metastatic disease is affected by multiple factors, including the number of nodes involved, whether the involvement is microscopic or macroscopic, and the presence of primary tumor ulceration.62 Of patients with clinically palpable nodal metastases, 70% to 90% will have distant metastases at presentation, and 5-year survival ranges from 6% to 40% in published series.63โ65 There is little contention that regional lymphadenectomy is indicated for staging information, local disease control, and salvage in a subset of patients. Although there is no prospective clinical trial data evaluating survival outcomes with therapeutic lymph node dissection (TLND) for palpable disease, approximately one in five patients will attain 10-year survival, confirming that not all patients have occult distant disease, and thus regional eradication should be pursued.66 This is particularly important given recent advances in medical oncologic approaches, as surgical nodal extirpation may provide the added benefit of tumor debulking.
For melanoma patients with microscopic nodal involvement, the application of lymphoscintigraphy and SLNB resulted in a paradigm shift in treatment. Prior to the advent of this technique, patients either underwent immediate ELND, or were observed for development of nodal disease. Several randomized controlled trials evaluating immediate versus delayed nodal dissection were performed in patients with normal regional nodes with mixed findings.67,68 Among patients with normal regional nodes, only 20% will have positive micrometastases on immunohistochemical analysis.69 MSLT-I showed a disease-free and disease-specific survival advantage with immediate completion lymph node dissection (CLND) compared to observation among patients with regional nodal disease, though it remains an ongoing question as to whether comparison only of node-positive patients in the two arms is valid.
In addition, it remains open to the question whether patients with positive SLNB benefit from CLND. Approximately 80% of patients with positive SLNB will not have additional metastatic nodal disease based on routine pathologic analysis of CLND specimens.70 The DeCOG-SLT phase 3 trial attempted to further answer this question by randomizing patients with positive SLNB to either immediate CLND versus observation. The trial was stopped early and was underpowered, though no significant difference in distant-metastasis-free survival was found.71 The MSLT-II is ongoing and similarly randomizes patients with positive SLNB to observation versus CLND. The trial is slated to finish in 2022 and will hopefully have sufficient power to address this question. Thus, although CLND contributes to staging, its effect on regional disease control and overall survival are not definitively established.
Attempts have been made to predict nonsentinel node positivity based on clinicopathologic features in order to ascertain which patients with positive SLNB may
benefit from CLND. Factors that have been shown to predict nonsentinel node involvement include SLN tumor burden, number of positive nodes, and primary lesion thickness and ulceration.70,72 In such settings, the NCCN recommends consideration of CLND in patients with positive SLNB.18