Practice Patterns and Prognostic Value of Sentinel Lymph Node Biopsy for Thick Melanoma: A National Cancer Database Study

Background. Sentinel lymph node biopsy (SLNB) has been somewhat controversial for patients with a diagnosis of thick (> 4 mm) melanoma. This study aimed to characterize the national practice pattern in performing SLNB for this patient population and to determine the predictors and prognostic value of nodal positivity using population-level data. Methods. Patients with a diagnosis of clinically nodenegative, thick melanoma (2010-2015) were identified using the National Cancer Database. Factors associated with performing regional nodal evaluation were characterized. Predictors of nodal positivity were determined using multivariable logistic regression. Overall survival (OS) was estimated using standard statistical methods. Results. Of 9847 study patients, 7513 (76.3%) underwent SLNB. The patients who underwent nodal evaluation were younger (median age, 66 vs 81 years; P < 0.001), less likely to have comorbid conditions (19.6% vs 26.0%; P < 0.001), more often privately insured (40.4% vs 16.4%; P < 0.001), and more frequently treated at an academic center (49.5% vs 43.9%; P < 0.001). Among those who underwent nodal evaluation, 25.5% had metastatic nodes. Multivariable regression identified age, Charlson-Deyo score, primary location, ulceration, mitoses, vertical growth phase, and lymphovascular invasion as independent predictors of nodal positivity, but with only moderate predictive accuracy (optimism-adjusted area under the curve, 0.684). Furthermore, compared with node negativity, node positivity was significantly associated with decreased OS (hazard ratio, 2.05; P < 0.001). Conclusion. Although nodal status provides important prognostic information, at a national level, nearly one fourth of patients with clinically node-negative, thick melanoma do not undergo SLNB. Appropriate pathologic staging would allow these high-risk patients to be candidates for effective adjuvant therapy.