Serum tumor marker levels at the development of intracranial metastasis in patients with lung or breast cancer

Intracranial metastasis (IM) is observed in various cancers, including in lung and breast cancer, and its timely diagnosis is required for successful patient treatment. Various tumor serum markers, such as carcinoembryonic antigen (CEA), pro-gastrin-releasing peptide (ProGRP), neuron-specific enolase (NSE), and cancer antigen 15-3 (CA15-3), serve not only as prognostic indicators in lung and breast cancer but also as risk factors for IM development. This study is the first to assess a subgroup of cancer patients with IM that did not show elevated serum tumor marker levels. This retrospective study included 53 patients with lung or breast cancer in which IM was detected by enhanced brain magnetic resonance imaging between January 2013 and December 2018. IM was classified into three types [parenchymal metastasis (PM), leptomeningeal metastasis and dural metastasis]. Serum CEA level was measured using an electrochemiluminescence immunoassay (ECLIA) or chemiluminescent immunoassay. Plasma ProGRP level was measured using a chemiluminescent enzyme immunoassay (CLEIA), and the serum NSE level was measured using ECLIA. The serum CA15-3 level was measured using CLEIA. Univariate and multivariate analyses were performed using Pearson's χ test and logistic regression analysis, respectively. Among the total 53 patients, 15 patients (28.3%) did not show elevated serum tumor marker levels. Univariate analysis showed that the patients with PM only significantly correlated with no increasing tumor marker level compared with other IM types (P=0.030), as well as female patients and patients without symptoms (P=0.010 and 0.046, respectively). Multivariate showed that the patients with PM only and female patients significantly correlated with no increasing tumor marker level (P=0.038 and 0.014, respectively). Our findings describe a subgroup of lung and breast cancer patients with IM that do not show elevated tumor marker levels, indicating the need for the identification of novel indicators for IM or increased monitoring of these patients.