MelRisk: Using the Neutrophil-to-Lymphocyte Ratio to Improve Risk Prediction Models for Metastatic Cutaneous Melanoma in the Sentinel Lymph Node

Abstract Background Identifying metastatic melanoma in the sentinel lymph node (SLN) is important. However, 80% of SLN biopsies are negative and 11% of patients develop complications. The neutrophil-lymphocyte ratio (NLR) is a biomarker of micrometastatic disease which could improve prediction models for SLN status. We externally validate existing models and developed ‘MelRisk' to better predict SLN metastasis. Methods Models were externally validated using data from a multicentre cohort study of 1,251 adults. Additionally, we developed and internally validated a new prognostic score `MelRisk', using candidate predictors derived from the literature. Results The Karakousis model had a C-statistic of 0.58 (95% CI 0.54, 0.62). The Sondak model had a C-statistic of 0.57 (95% CI 0.53, 0.61). The MIA model had a C-statistic of 0.60 (95% CI 0.56, 0.64). Our ‘MelRisk' model (which uses Breslow thickness, ulceration, age, anatomical site, and the NLR) had an adjusted C-statistic of 0.63 (95% CI 0.56, 0.64). Conclusion Our prediction tool is freely available in the Google Play Store and Apple App Store, and we invite colleagues to externally validate its performance.