In addition, some studies have identified biomarkers associated with lung cancer (Seijo et al., 2019) that can be used in disease diagnosis and treatment response, such as carcinoembryonic antigen (CEA; Hammarström, 1999) and cytokeratin fraction 21-1 (CYFRA 21-1; Shirasu et al., 2018). This evidence concerns the gene CEACAM5 and lung cancer.