[S100 protein in tumours of the central nervous system]

S100 protein has been detected in glials cells. The subject of this study is to evaluate the usefulness of serum levels of S100 as tumor marker for the screening diagnosis and follow up in patients with CNS tumors.

57 patients were studied with tumors of the CNS: 24 multiform glioblastomas (GM), 11 anaplastic astrocytomas (AA), 3 oligodedrogliomas, 1 pinealoblastoma, 3 neurinomas, 1 low grade glioma and 13 brain metastasis of other extraneural primary tumors. 25 healthy people have been taken as control group. The S100 was analyzed by an immunoradiometric assay (IRMA) with 125 Iode. The cut off value was 0.2 g/L.

The presurgical mean serum values of S100 didn t differ of the mean values of the control group (0.08 and 0.07 g/L, respectively). In the surgical treated patients with residual tumoral or recurrent tumors, the values of S100 increases to 38.9% in GM, 57.11% in AA and 76.9% in brain metastasis. In GM the serum values are significantly higher in patients with active tumor before receiving treatment with chemotherapy, radiotherapy or radiosurgery (p < 0.05). The values decreses to normal levels after response to oncological therapies. During the follow up (mean 551 days), the global sensitivity of S100 for progression of the disease was 47.5% and specificity was 90% with a correspondence between S100 and disease s evolution of 56%.

S100 protein is not useful in the initial diagnosis of tumoral disease but it could be of help in the follow up of the disease because it decreases with successful treatments and increases at the time when the tumor progress.