Comparative study of serum 6-hydroxy-5-methoxyindole-2-carboxylic acid, 5-S-cysteinyl-dopa, and lactate dehydrogenase levels as markers for malignant melanoma

Background With the development of novel therapies for advanced malignant melanoma (MM), biomarkers that can accurately reflect the progression of MM are needed. Recently, we have developed a method to measure the serum levels of 6-hydroxy-5-methoxyindole-2-carboxylic acid (6H5MI2C), a melanin-related metabolite, using mass spectrometry and reported that it may be a potential marker for MM. Objective In the present study, we compared the usefulness of serum levels of 6H5MI2C, 5-S-cysteinyl-dopa (5-S-CD), and lactate dehydrogenase (LD) as tumor markers for MM (n = 63). Results Among the three markers, only 6H5MI2C was significantly elevated in the metastatic group (stages III and IV) compared to the non-metastatic group (stages 0 to II). Additionally, 6H5MI2C with a cut-off level of 1.00 ng/mL showed higher sensitivity for metastatic MM than 5-S-CD and LD. Conclusions Thus, serum 6H5MI2C level has the potential to be a good marker for MM in comparison to 5-S-CD and LD.