Predicting sentinel and residual lymph node basin disease after sentinel lymph node biopsy for melanoma.

BACKGROUND: The selection of patients for sentinel lymph node biopsy (SNB) and selective lymphadenectomy for histologically positive sentinel lymph nodes (SLND) are areas of debate. The authors of the current study attempted to identify predictors of metastases to the sentinel and residual nonsentinel lymph nodes in patients with melanoma.

METHODS: The Indiana University Interdisciplinary Melanoma Program computerized database was queried to identify all patients who underwent SNB for clinically localized cutaneous melanoma. Demographic, surgical, and histopathologic data were recorded. Univariate and multivariate logistic regression analyses were performed to identify associations with SNB and nonsentinel lymph node positivity. Classification tree and logistic procedures were performed to identify the ideal tumor thickness cutpoint at which to perform SNB.

RESULTS: Two hundred seventy-five SNB procedures were performed to stage 348 regional lymph node basins for occult metastases from melanoma. Of the 275 melanomas, 54 (19.6%) had a positive SNB, as did 58 of 348 basins (16.7%). Classification and logistic regression analysis identified a Breslow depth of 1.25 mm to be the most significant cutpoint for SNB positivity (odds ratio 8. 8:1; P = 0.0001). By multivariate analyses, a Breslow thickness cutpoint >/= 1.25 mm (P = 0.0002), ulceration (P = 0.005), and high mitotic index (> 5 mitoses/high-power field; P = 0.04) were significant predictors of SNB results. SLND was performed in 53 SNB positive patients, 15 of whom (28.3%) had at least 1 additional positive lymph node. SLND positivity was noted across a wide range of primary tumor characteristics and was associated significantly with multiple positive SN, but not with any other variable. SNB result correlated significantly with disease free and overall survival.

CONCLUSIONS: Patients with a Breslow tumor thickness >/= 1. 25 mm, ulceration, and high mitotic index are most likely to have positive SNB results. SLND is recommended for all patients after positive SNB because it is difficult to identify patients with residual lymph node disease.