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End Nodes . . .

Tumor burden predicts additional involvement, perhaps preventing unnecessary complete lymph node dissections.

Standard practice in melanoma treatment now dictates ongoing observation of the mapped nodal basin if all identified sentinel lymph nodes (SLNs) are negative for melanoma, and complete therapeutic lymph node dissection (cTLND) if any SLN contains disease. Because cTLND involves considerable morbidity, and because lymph nodes remaining in the basin after SLN biopsy are often uninvolved, an accurate method for predicting risk for subsequent disease is needed. Investigators sought factors that predict additional involvement.

Among 2203 patients who underwent SLN biopsy, 359 (16.3%) had at least one pathologically positive SLN; 343 of these patients (96%) subsequently underwent cTLND. Pathologically positive non-SLNs were detected in the cTLND specimen in 48 of these patients (14.0%). Statistically significant predictors of further disease included the following: (1) having only one SLN, versus having at least three SLNs, harvested; (2) age older than 50; (3) tumor thickness greater than 2 mm; (4) Clark level higher than III; (5) presence of primary melanomas on a lower extremity; and (6) greatest diameter of the single largest SLN deposit greater than 10 mm. There was a trend toward significance for a higher number of positive SLNs.

In a regression model, scores were assigned to the most significant correlates of non-SLN positivity: tumor thickness (0 or 1), largest SLN metastatic focus (0, 1, 2, or 3), and number of SLNs harvested (0, 1, or 2). Scores of 0, 1–2, 3–4, and 5–6 correlated with, respectively, 0%, 4.0%, 22.2%, and 46.7% likelihood of non-SLN involvement.

Comment: This is one model for predicting non-SLN involvement after a positive SLN biopsy, and there will undoubtedly be others. The basic message from these findings is surprisingly simple: Tumor burden still matters, be it primary tumor thickness or maximal size of nodal focus. When more nodes are removed in SLN biopsy (e.g., >3), a "mini cTLND" has likely already occurred, and additional disease has been removed during the biopsy itself. The study has two limitations: Some testing of the performance of the model would have been nice, and a separate, independent validation set should have been included. Most importantly, a prospective trial will be needed before changing current practice.

— Hensin Tsao, MD, PhD

Published in Journal Watch Dermatology October 10, 2008

Citation(s):

Gershenwald JE et al. Microscopic tumor burden in sentinel lymph nodes predicts synchronous nonsentinel lymph node involvement in patients with melanoma. J Clin Oncol 2008 Sep 10; 26:4296.

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