S100beta as a predictor of brain metastases: brain versus cerebrovascular damage

The identification of brain metastases in patients with malignant disease has important implications for determining their treatment and prognosis. Asymptomatic metastatic brain tumors may be detected by surveillance imaging techniques, but longitudinal follow-up of patients who are at risk is sporadic primarily due to cost. Because the development of brain metastases is accompanied and detected by extravasation of contrast agents across the blood-brain barrier (BBB), the authors hypothesized that peripheral analysis of the BBB indicator S100beta may be useful as a screening tool for brain metastases in patients who have no neurologic symptoms.

Thirty-eight patients were enrolled for the current study. All patients had newly diagnosed lung carcinoma and had no neurologic symptoms or known history of brain metastasis. Patients underwent an initial magnetic resonance imaging (MRI) scans and S100beta blood tests. S100beta tests were repeated in a subset of patients at the time of routine follow-up MRI scans.

Based on imaging studies and on serum S100beta analyses, the patients were divided in 3 categories: 1) patients with normal S100beta levels (0.08 +/- 0.02 microg/L; n = 22 patients) and normal MRI scans; 2) patients with elevated S100beta levels (0.5 +/- 0.28 microg/L; n = 8 patients) and pronounced microvascular changes on MRI scans but with no metastases; and 3) patients with elevated S100beta levels (0.28 +/- 0.19 microg/L; n = 7 patients) and metastatic brain tumor(s) on MRI scans.

Because of the significant overlap in S100beta levels between patients with cerebral microvascular diseases and patients with brain metastases, the authors concluded that the serum S100beta level may be used as a surveillance tool to predict or detect brain metastases if appropriate prescreening radiologic tests are obtained and if patients who are candidates for false-positive results are identified and excluded.