Patterns and Predictors of Sentinel Lymph Node Biopsy Utilization in High- and Low-Risk Thin Melanomas

Background Sentinel lymph node biopsy (SLNB) is recommended for patients with >10% risk of metastasis and not for those with <5% risk. The National Comprehensive Cancer Network acknowledges that individualized risk assessment tools, such as the Melanoma Institute of Australia (MIA) sentinel node metastasis risk model, may aid decision-making. We hypothesized that SLNB utilization would not differ substantially between the pre- and post-publication eras of the MIA model. Methods We retrospectively reviewed National Cancer Database data from 2018 to 2022. Patients with thin melanomas (<1.0 mm Breslow depth) were classified into <5% or >10% sentinel node positivity risk groups using the MIA model. Demographic and pathologic characteristics were examined. Results Of 58,119 patients with thin melanomas, 43,551 met inclusion criteria after excluding 14,491 with intermediate (5–10%) risk. Among 3949 with >10% risk, 62.9% had SLNB and 37.1% had SLNB omitted. Conversely, among 39,602 with <5% risk, 13.7% received SLNB. Tumor thickness, ulceration, and mitotic rate were significant predictors of SLNB in both groups. Increasing age was associated with lower odds of SLNB only in the low-risk cohort. Notably, SLNB utilization changed minimally following publication of the MIA model, increasing by <1% in the <5% group and 4% in the >10% group. Conclusions Before and after MIA model publication, SLNB was underutilized in high-risk patients and overutilized in low-risk patients. Utilization was primarily driven by tumor-specific factors. Our findings suggest limited early adoption of the model and highlight the need for improved dissemination of personalized risk stratification tools.