The sensitivity of CSF cytology, the standard method for diagnosis of leptomeningeal metastases (LM), is low. Serum cancer antigen 15-3 (CA 15-3) is frequently used for the monitoring of patients with breast cancer (BC) and is a laboratory test available in most centers. The aim of the current study was to determine the feasibility of measuring CSF CA 15-3 and CA 15-3 CSF/serum ratio in patients with BC-related LM. Serum and CSF CA 15-3 values were evaluated in 20 BC patients with LM (Group 1), 20 patients with LM from other primary cancers (Group 2), 20 BC patients with parenchymal brain metastases only (Group 3) and 20 controls (Group 4). CSF and serum were collected on the same day. Serum and CSF CA 15-3 were assessed by an automatized immuno-enzymatic technology (TRACE(®) technology, KRYPTOR Automate, Brahms Society, France). In univariate analysis, BC patients with LM (Group 1) compared to other groups, a significantly elevated serum CA 15-3 (median 51 U/ml, range 12-2819) and CSF CA 15-3 (median 8.7 U/ml, range 0.1-251) was observed. Additionally, the CSF/serum ratio of CA 15-3 was significantly higher in this group of patients (median 0.18, range 0.002-4.40). Multivariate analysis identified a cut-off for CSF CA15-3 with 80 % sensitivity and 70 % specificity.
Conclusions: The current study confirms the feasibility of determining CSF CA 15-3 using a widely available technology. Evaluation of the CSF CA 15-3 may be useful in the diagnosis and management of BC-related LM but further studies are needed.