Sentinel Lymph Node Biopsy Is Prognostic in Thickest Melanoma Cases and Should Be Performed for Thick Melanomas

Sentinel lymph node biopsy (SLNB) is recommended for intermediate thickness melanoma, but for thick melanoma, guidelines are less definitive about the use of SLNB in this population. We present a study on thick melanoma evaluating for prognostic factors.

The Sentinel Lymph Node Working Group database was queried for thick (> 4 mm) melanoma cases that had a SLNB from 1993 to 2018. Clinicopathologic characteristics were correlated with SLN status and melanoma-specific survival (MSS).

There were 1235 patients. Median follow-up was 28 months. Median thickness was 5.9 mm, with 956, 175, and 104 cases presenting thickness > 4-8, > 8-12, and > 12 mm, respectively. SLN metastases were seen in 439 of 1235 (35.5%) cases and in 33.9%, 40.6%, and 42.3% of melanomas > 4-8, > 8-12, and > 12 mm, respectively. In each thickness group, MSS was significantly worse for SLN-positive compared with SLN-negative cases (all P < 0.005). Multivariable analysis showed that SLN metastasis, male gender, increasing thickness, lymphovascular invasion, and microsatellitosis significantly predicted worse MSS for melanomas > 4-8 mm, with SLN metastasis showing the greatest risk (HR 2.17, 95% CI 1.64-2.87, P < 0.0001). For melanomas > 8 mm, only SLN metastasis significantly predicted MSS (> 8-12 mm: HR 3.93, 95% CI 2.00-7.73, P < 0.0001; > 12 mm: HR 3.58, 95% CI 1.56-8.22, p < 0.0027).

Thick melanoma patients with SLN metastasis have significantly worse MSS compared with SLN-negative patients, even in the thickest cases, and SLN status is the most powerful and/or only predictor of MSS. Given these results, SLNB shows important prognostic value in this population and is indicated for clinically localized thick melanoma.