Serum S100beta protein as a marker of disease activity in patients with malignant melanoma.

The purpose of the study was to evaluate serum S100beta protein as a marker of disease activity in patients with malignant melanoma (MM) and compare it with serum alkaline phosphatase (ALP) and lactate dehydrogenase (LDH). One hundred sixty-four patients with MM, stages I-IV according to the American Joint Committee on Cancer (AJCC), were studied. Recurrent disease was categorized as active (AD) if metastases were evident clinically or with imaging investigations and inactive (ID) if no metastases were apparent at the time of sample collection. The sensitivity and specificity of S100beta, LDH, and ALP for discrimination between AD and ID were calculated using receiver-operating characteristic curve (ROC) analysis. Serum S100beta, LDH, and ALP concentrations were significantly higher in AD compared to ID. Serum S100beta protein was the best discriminator between AD and ID, the areas under the ROC curve being 0.89, 0.71, and 0.70 for S100beta, LDH, and ALP, respectively. Serum S100beta and LDH levels (both p < 0.0001) and serum ALP levels (p = 0.0014) corresponded with the number of metastatic sites involved. Using a cutoff point of 0.20 microg/L for serum S100beta protein, a specificity of 93% with a sensitivity of 68% was obtained for AD in MM. In stage IV disease, S100 was an independent predictor of survival in univariate (p = 0.001; hazard ratio = 1.0156) and multivariate (p = 0.038; hazard ratio = 1.0108) analyses. Serum S100beta protein is a better indicator of disease activity in MM than LDH or ALP and is an independent predictor of survival in stage IV disease.