Total Sentinel Lymph Node Tumor Size Predicts Nonsentinel Node Metastasis and Survival in Patients with Melanoma

Abstract

In patients with a primary melanoma ≥1.0mm in Breslow thickness, the rate of metastasis to regional lymph nodes, as determined by sentinel node biopsy (SLNB), is approximately 20%. Among the patients with a positive SLNB result, however, only approximately 20% have tumor identified in additional non-SLNs. Therefore, many melanoma patients are still subjected to the morbidity of a complete lymph node dissection (CLND) without obvious benefit. In the current study, we analyzed the clinical and pathologic features of melanoma patients with positive SLNBs treated at the Melanoma Institute Australia. The aim was to correlate clinical and pathologic features of both the primary melanoma and the SLN metastases, including total SLN metastasis, with non-SN metastasis and (disease specific and overall) survival. Total SLN tumor size was obtained by adding the largest diameters of all individual metastatic deposits within the SLN. Clinicopathological variables analyzed included patient age at the time of diagnosis, primary tumor characteristics (histologic type, Breslow thickness, ulceration, mitotic rate, site of primary tumor), and SLNB characteristics (date of SLNB procedure, location of LN field, number of draining LN fields, number of SLNs harvested, number of positive SLNs, size of largest metastatic deposit, total metastatic deposit size, location of metastasis within the SLN, extra nodal extension (ENE), and number of metastatic deposits within the SLN). The correlation between each of the predictor variables and outcome was determined by univariate analysis. The predictor variables that correlated with NSLN metastasis with a p value<0.10 on univariate analysis were then entered into a multivariate model. There were 606 patients with a positive SNSNB result who proceeded to a CLND. The median number of NSNs in CLND specimens was 18 and the median number of positive NSLNs was 2.68. Of the patients with SN metastasis, 23.5% also had NSLN metastasis on CLND. Total SLN tumor size was significantly correlated to NSLN metastasis, melanoma-specific survival and overall survival on both univariate and multivariate analyses. Total SN tumor size predicts the likelihood of non-SLN metastasis, and also predicts survival outcome.