Role for lymphatic mapping and sentinel lymph node biopsy in patients with thick (≥4 mm) primary melanoma

Background: Historically, patients with thick (≥4 mm) primary melanoma have not been considered candidates for elective lymph node dissection, because their risk for occult distant disease is significant. Sentinel lymph node (SLN) biopsy offers an alternative approach to assess disease in the regional nodal basin, but no studies have specifically addressed the role for this technique in patients with thick melanoma. Although adjuvant therapy benefits patients who develop nodal metastases, data that supports its routine use in all patients with thick melanoma is both limited and controversial. This study was performed to determine whether pathological status of the SLN is an important risk factor in this heterogeneous group and, thus, provides a rationale for SLN biopsy. Methods: The records of 131 patients with primary cutaneous melanoma whose primary tumors were at least 4 mm thick and who underwent lymphatic mapping and SLN biopsy were reviewed. Several known prognostic factors, i.e., tumor thickness, ulceration, Clark level, location, sex, as well as SLN pathological status were analyzed with respect to disease-free and overall survival. Results: Lymphatic mapping and SLN biopsy was successful in 126 (96%) of 131 patients who underwent the procedure. In 49 patients (39%), the SLN biopsy was positive by conventional histology, although it was negative in 77 patients (61%). The median follow- up was 3 years. Although presence of ulceration and SLN status were independent prognostic factors with respect to disease-free and overall survival, SLN status was the most powerful predictor of overall survival by univariate and multivariate analyses. Conclusions: Lymphatic mapping and SLN biopsy is a highly accurate method of staging lymph node basins at risk for regional metastases in patients with thick melanoma and identifies those patients who may benefit from earlier lymphadenectomy as well as patients with a more favorable prognosis. Pathological status of the SLN in these patients with clinically negative nodes is the most important prognostic factor for survival and is essential to establish stratification criteria for future adjuvant trials in this high-risk group.