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Sentinel Lymph Node Biopsies for Thin Melanomas

Summary and Comment |
January 8, 2014

Sentinel Lymph Node Biopsies for Thin Melanomas

  1. Hensin Tsao, MD, PhD

SLNB should be considered in patients with thin melanomas and Breslow thickness >0.75 mm, Clark level IV, or ulceration.

  1. Hensin Tsao, MD, PhD

Surgeons commonly recommend sentinel lymph node biopsy (SLNB) for tumors ≥1 mm in thickness. Some thin melanomas have poor outcomes, recurring as much as 10 years after initial diagnosis, with melanoma-related death in some. The American Joint Committee on Cancer staging manual recommends SLNB for patients with “thin IB” tumors (i.e., lesions less than 1 mm thick but with such adverse prognostic indicators as ulceration and high mitotic rate). The prognostic utility of SLNB in individuals with thin IB tumors is not currently clear. These investigators conducted a large, multi-institutional study to determine factors predictive of SLN metastasis in thin melanomas.

Retrospective review of an international database identified 1250 patients with a thin melanoma (primary tumor thickness <1 mm) and SLNB performed between 1994 and 2012. Breslow thickness, Clark level, ulceration, regression status, and mitotic rate were evaluated. Sixty-five patients had a positive SLNB. The clinically useful predictors for a positive sentinel node in thin melanoma were Breslow thickness >0.75 mm, Clark level IV, and ulceration. Neither mitotic rate ≥1/mm2 nor absence of regression predicted SLN disease in any of the multivariable models. Median follow-up was 2.6 years. Among the 65 positive SLN patients, 4 melanoma-related deaths occurred (6.2%). In the negative SLNB group, there were 19 melanoma-related deaths (2.0%).

Comment

This study, one of the largest evaluating sentinel lymph node biopsy of thin melanomas, is important, because most patients present with thin melanomas, a substantial fraction of which fall into the thin IB category. The risk for death in these cases was quite low, and, as one would expect, risk for nodal disease increased with increasing thickness. The 91% overall 5-year survival rate in patients with positive SLN was lower than in patients with uninvolved nodes, but oddly, relapse-free survival rates did not differ statistically between groups. Based on these results, I conclude that SLNB should be considered in patients with thin melanomas and coexisting adverse features of Breslow thickness >0.75 mm, Clark level IV, and ulceration. It is imperative to let patients know that even with positive nodes, the outcome is not nearly as grim as it might be for thicker tumors. With longer follow-up, it is possible that survival rates will drop over time and that positive versus negative node curves will further diverge.

  • Disclosures for Hensin Tsao, MD, PhD at time of publication Consultant / advisory board Genentech; Quest Diagnostics; WorldCare Clinical Grant / research support NIH; Department of Defense; American Skin Association Editorial boards British Journal of Dermatology; Journal of the American Academy of Dermatology; Journal of Investigative Dermatology Leadership positions in professional societies American Academy of Dermatology (Chair, Skin Cancer and Melanoma Committee); American Board of Dermatology (Director)

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