The serum isocitrate dehydrogenase 2 (IDH2) can be a new and reliable biomarker for the diagnosis and prognosis of NSCLC.11 Currently, some tumor markers are used to detect lung cancer, such as carcinoembryonic antigen (CEA), serum cytokeratin 19 fragment (Cyfra 21-1) and progesterone-releasing peptide (pro-GRP). Here, CEACAM5 is linked to lung cancer.