Predictors of Sentinel Lymph Node Metastasis Identified in Thin Melanomas
In a study reported in the Journal of Clinical Oncology, Dale Han, MD, of Moffitt Cancer Center, and colleagues in the Sentinel Lymph Node Working Group attempted to identify factors predictive of sentinel lymph node metastasis in thin melanomas. They found that Breslow thickness ≥ 0.75 mm, Clark level ≥ IV, and ulceration significantly predict sentinel lymph node disease, with the findings suggesting that sentinel lymph node biopsy is indicated for thin melanomas ≥ 0.75 mm.
The study involved retrospective review of the Sentinel Lymph Node Working Group database from 1994 to 2012. A total of 1,250 patients who had a sentinel lymph node biopsy and melanomas ≤ 1 mm were identified. Clinicopathologic characteristics were analyzed for association with sentinel lymph node status and outcome.
Predictors of Sentinel Lymph Node Disease
Among the 1,250 patients, sentinel lymph node metastases were found in 65 (5.2%). On univariate analysis, proportions of sentinel lymph node–positive vs sentinel lymph node–negative patients differed significantly for Breslow thickness (≥ 0.75 mm in 86.2% vs 70.5% and < 0.75 mm in 13.8% vs 29.5%; P ≤ .01), Clark level (≥ IV in 68.4% vs 49.9% and < IV in 31.6% vs 50.1%; P < .01), ulceration (present in 18.3% vs 8.4% and absent in 81.7% vs 91.6%; P < .01), and regression (present in 10.6% vs 23.3% and absent in 89.4% vs 76.7%; P = .04).
Multivariate Analysis
When these four variables and mitotic rate were included in multivariate analysis, Breslow thickness ≥ 0.75 mm (odds ratio [OR] = 2.21, P = .03), Clark level ≥ IV (OR = 1.80, P = .05), and ulceration (OR = 2.51, P = .01) remained significant predictors of sentinel lymph node metastasis, whereas absence of regression (OR = 1.74, P = .18) and mitotic rate ≥ 1/mm2 (OR = 1.01, P = .97) did not. Breslow thickness ≥ 0.75 mm, Clark level ≥ IV, and ulceration were present in 6.3%, 7.0%, and 11.6% of sentinel lymph node–positive patients, respectively.
Melanomas < 0.75 mm had positive sentinel lymph node rates of < 5% regardless of Clark level and ulceration status. In melanomas ≥ 0.75 mm, sentinel lymph node metastasis rates were 8.2% and 3.7% for Clark level ≥IV vs < IV melanomas, whereas in tumors < 0.75 mm, sentinel lymph node metastasis rates were 2.5% and 2.7% for Clark level ≥ IV vs < IV melanomas. Clark level ≥ IV was present in only 68.4% of sentinel lymph node–positive patients with available Clark level data, with 92.3% of these patients having melanomas ≥ 0.75 mm.
In tumors ≥ 0.75 mm, sentinel lymph node disease was present in 14.7% of ulcerated tumors and 6% of nonulcerated tumors. For tumors < 0.75 mm, sentinel lymph node disease was present in 3.7% of ulcerated tumors and 2.6% of nonulcerated tumors. Ulceration was present in only 18.3% of 60 sentinel lymph node–positive patients with available ulceration data, with 90.9% of these patients having melanomas ≥ 0.75 mm.
Survival Outcomes
Median follow-up was 2.6 years. There was no difference in recurrence-free survival between sentinel lymph node–positive and sentinel lymph node–negative patients (5-year recurrence-free survival 85.8% vs 90.6%, P = .36). Melanoma-specific survival was significantly worse in sentinel lymph node–positive patients (5-year melanoma-specific survival 90.8% vs 97.8%, P < .01).
The investigators concluded: “Breslow thickness ≥ 0.75 mm, Clark level ≥ IV, and ulceration significantly predict [sentinel lymph node] disease in thin melanoma. Most [sentinel lymph node] metastases (86.2%) occur in melanomas ≥ 0.75 mm, with 6.3% of these patients having [sentinel lymph node] disease, whereas in melanomas < 0.75 mm, [sentinel lymph node] metastasis rates are < 5%. By using a 5% metastasis risk threshold, [sentinel lymph node] biopsy is indicated for melanomas ≥ 0.75 mm, but further study is needed to define indications for [sentinel lymph node] biopsy in melanomas < 0.75 mm.”
Dr. Han and Jonathan S. Zager, MD, of Moffitt Cancer Center, contributed equally to the work and Stanley P. Leong, MD, of California Pacific Medical Center and Research Institute, is the corresponding author for the Journal of Clinical Oncology article.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
