CEACAM5 and lung cancer: The two groups were compared in terms of baseline data and lung cancer biomarkers, including carcinoembryonic antigen (CEA), neuron-specific enolase (NSE), cytokeratin 19 fragment 21–1 (CYFRA 21–1), squamous cell carcinoma antigen (SCCA), and pro-gastrin-releasing peptide (ProGRP).