Sentinel lymph node biopsy for melanoma: Experience with 234 consecutive procedures

Sentinel lymph node biopsy is increasingly used to identify occult metastas es in regional lymph nodes of patients with melanoma. Selection of patients for sentinel lymph node biopsy and subsequent lymphadenectomy is an area o f debate. The purpose of this study was to describe a large clinical series of these biopsies for cutaneous melanoma and to identify patients most lik ely to gain useful clinical information from sentinel lymph node biopsy. Th e Indiana University Melanoma Program computerized database was queried to identify all patients who underwent this procedure for clinically localized cutaneous melanoma. It was performed using preoperative technetium Tc 99m lymphoscintigraphy and isosulfan blue dye. Pertinent demographic, surgical, and histopathologic data were recorded. Univariate and multivariate logist ic regression and classification table analyses were per-formed to identify clinical variables associated with sentinel node and nonsentinel node posi tivity. In total, 254 biopsy procedures were performed to stage 291 nonpalp able regional lymph node basins. Mean Breslow's thickness was 2.30 mm (2.08 mm for negative sentinel lymph node biopsy, 3.18 mm for positive). The mea n number of sentinel nodes removed was 2.17 nodes per basin (range, 1 to 8) . Forty-seven of 254 melanomas (20.1 percent) and 50 of 291 basins (17.2 pe rcent) had a positive biopsy. Positivity correlated with AJCC tumor stage: T1, 3.6 percent; T2, 8.1 percent; T3, 27.4 percent; T4, 44 percent. By univ ariate logistic regression, Breslow's thickness (P = 0.003, continuous vari able), ulceration (P = 0.003), mitotic index greater than or equal to 6 mit oses per high power field (p = 0.008), and Clark's level (p = 0.04) were si gnificantly associated with sentinel lymph node biopsy result. By multivari ate analysis, only Breslow's thickness (P = 0.02), tumor ulceration (p = 0. 02), and mitotic index (P = 0.02) were significant predictors of biopsy pos itivity. Classification table analysis showed the Breslow cutpoint of 1.2 m m to be the most efficient cutpoint for sentinel lymph node biopsy result ( p = 0.0004) Completion lymphadenectomy was performed in 46 sentinel node-po sitive patients; 12 (26.1 percent) had at least one additional positive non sentinel node. Nonsentinel node positivity was marginally associated with t he presence of multiple positive sentinel nodes (p = 0.07). At mean follow- up of 13.8 months, four of 241 sentinel node-negative basins demonstrated s ame-basin recurrence (1.7 percent). Sentinel lymph node biopsy is highly re liable in experienced hands but is a low-yield procedure in most thin melan omas. Patients with melanomas thicker than 1.2 mm or with ulcerated or high mitotic index lesions are most likely to hale occult lymph node metastases by sentinel lymph node biopsy. Completion therapeutic lymphadenectomy is r ecommended after positive biopsy because it is difficult to predict the pre sence of positive nonsentinel nodes.