Optimal cut-off values for CYFRA 21-1 expression in NSCLC patients depend on the presence of benign pulmonary diseases.

Background: Serum cytokeratin fragment 21-1 (CYFRA 21-1) expression levels are reported to be useful in the diagnosis of lung cancer, especially non-small cell lung cancer (NSCLC). However, the clinical value of CYFRA 21-1 as a tumor marker remains unclear, and no optimal cut-off value has been determined thus far. The purpose of this study was to establish a potential clinical cut-off value for serum CYFRA 21-1 as a diagnostic marker in patients with NSCLC.