Sentinel lymph node biopsy for melanoma: indications and rationale.

BACKGROUND: The disease status of regional lymph nodes is the most important prognostic indicator for patients with melanoma. Sentinel lymph node biopsy (SLNB) was developed as a technique to surgically assess the regional lymph nodes and spare node-negative patients unnecessary and potentially morbid complete lymphadenectomies.

METHODS: We reviewed the literature on SLNB for cutaneous melanoma to provide insight into the rationale for the current widespread use of SLNB.

RESULTS: Multiple studies show that the status of the SLN is an important prognostic indicator. Those with positive SLNs have significantly decreased disease-free and melanoma-specific survival compared with those who have negative SLNs. In the Multicenter Selective Lymphadenectomy Trial I (MSLT-I), in which patients with intermediate-thickness melanoma were randomized to SLNB (and immediate completion lymphadenectomy if the SLN was positive) vs observation (and a lymphadenectomy only after presenting with clinically evident recurrence), the 5-year survival rate was 72.3% for patients with positive sentinel nodes and 90.2% for those with negative sentinel nodes (P < .001). Although overall survival was not increased in patients who underwent SLNB compared with those who were randomized to observation, patients who underwent SLNB had a significantly increased 5-year disease-free survival rate compared with those who underwent observation alone (78.3% in the biopsy group and 73.1% in the observation group; P = .009). For those with nodal metastases, patients who underwent SLNB and immediate lymphadenectomy had an increased overall 5-year survival rate compared with those who had lymphadenectomy only after presenting with clinically evident disease (72.3% vs 52.4%; P = .004). Moreover, other studies show that for patients with thin melanomas <or= 1.0 mm, the overall survival rate is significantly worse for those with positive SLNs compared to those with negative SLNs. For thin melanomas, Breslow depth >or= 0.76 mm and increased mitotic rate have been shown to be associated with an increased incidence of SLN metastases.

CONCLUSIONS: SLNB provides important prognostic and staging data with minimal morbidity and can be used to identify regional node-negative patients who would not benefit from a complete nodal dissection. In our opinion, SLNB should be performed on most patients (with acceptable surgical and anesthesia risk) who have melanomas with a Breslow depth >or= 0.76 mm.