S100B PROTEIN, 5-S-CYSTEINYLDOPA AND 6-HYDROXY-5-METHOXYINDOLE-2-CARBOXYLIC ACID AS BIOCHEMICAL MARKERS FOR SURVIVAL PROGNOSIS IN PATIENTS WITH MALIGNANT-MELANOMA

Elevated levels of the phaeomelanin metabolite 5-S-cysteinyldopa and t he eumelanin metabolite 6-hydroxy-5-methoxyindole-2-carboxylic acid in urine and serum have been shown in previous studies to correlate with disseminated malignant melanoma. Immunohistochemical detection of S10 0B protein is an acknowledged method for the diagnosis of malignant me lanoma, and it has been suggested that rising serum levels of S100B pr otein are associated with the survival rate of patients with malignant melanoma. In the present study serum levels of S100B protein and urin ary concentrations of 5-S-cysteinyldopa and 6-hydroxy-5-methoxyindole- 2-carboxylic acid were measured in 91 patients with histopathologicall y verified malignant melanoma. At the time of sampling 13 patients wer e in clinical stage I, 13 in stage II and 65 in stage III. The urinary levels of the melanin metabolites were determined by automated high p erformance liquid chromatography, and the serum levels of S100B protei n by an immunoradiometric assay with two monoclonal antibodies. The ov erall survival rate was most strongly associated with the serum levels of S100B protein (P < 0.001), but there was also a significant correl ation to urinary levels of 5-S-cysteinyldopa (P < 0.001). A correspond ing association with urinary levels of 6-hydroxy-5-methoxyindole-2-car boxylic acid was found in only a very few patients with extremely high urinary concentrations. A statistically significant increase in relat ive hazard was found for S100B protein levels exceeding 0.6 mu g/l (P < 0.001), and predictably for patients in clinical stage III (P < 0.00 1). An analysis of S100B protein levels in patients in clinical stage III showed a significant correlation to survival (P = 0.005). Our stud y suggests that of the three biochemical tumour markers, S100B and to a lesser extent 5-S-cysteinyldopa have the greatest potential to be us ed as predictors of survival prognosis in patients with malignant mela noma.