Serum 5-S-cysteinyl-dopa levels as a predictive marker for the efficacy of nivolumab in advanced malignant melanoma

Purpose: With the recent developments in novel molecular targeted therapy such as immune-checkpoint blockades, serine/threonine-protein kinase B-Raf, and mitogen-activated protein kinase kinase inhibitors, the prognosis of advanced malignant melanoma has been improving. 5-S-cysteinyl-dopa (5-S-CD), a precursor of pheomelanin, has been previously revealed to be a useful biomarker for advanced-stage malignant melanoma, especially in patients with distant metastases. Here, we aimed to assess and compare the utility of serum 5-S-CD and lactate dehydrogenase levels as markers for predicting the effects of nivolumab in advanced malignant melanoma. Methods: Baseline serum 5-S-CD and lactate dehydrogenase levels in patients with unresectable stage IIIC and IV malignant melanoma treated with nivolumab (n = 21) were analyzed to determine their utility as predictive markers for survival. We also analyzed the prognostic value of these markers among patients with only stage IV malignant melanoma (n = 17). Results: Our analysis showed that patients with baseline serum 5-S-CD levels >25.0 nmol/L had significantly poor prognosis. In contrast, serum lactate dehydrogenase levels at the upper limit of the normal range did not exhibit such changes. Conclusions: Serum 5-S-CD levels have the potential to be an excellent predictive marker for the efficacy of nivolumab therapy in patients with advanced malignant melanoma.