Relative Change in S100 as a Biomarker of Survival in Patients With Metastatic Melanoma Treated With Pembrolizumab

Background/Aim: There is a lack of quality biomarkers of survival for patients with metastatic melanoma treated with immunotherapy. Although the baseline level of S100 has prognostic value, its role during/after therapy in survival is unclear. Patients and Methods: We evaluated patients with metastatic melanoma treated with pembrolizumab with the goal of analysing the relationship between a relative change in S100 level at 12 weeks of immunotherapy and survival. Results: Patients with a relative change in S100 level >145% at 12 weeks of immunotherapy had significantly shorter progression-free (5.1 vs. 18.5 months, p <= 0.0001) and overall survival (5.7 vs. 26.3 months, p<0.0001), further confirmed on multivariate analysis with hazard ratio of 32.25 (95% confidence interval=4.78-217.6, p=0.0004) for overall survival. Conclusion: A relative change in S100 level might be useful as a more precise biomarker of survival for patients with metastatic melanoma treated with pembrolizumab.