As well, pre-diagnostic blood samples from ever-smokers who subsequently developed lung cancer were found, in a recent study, to have elevated levels of 4 proteins, cancer antigen 125 (CA125), carcinoembryonic antigen (CEA), cytokeratin-19 fragment (CYFRA 21-1) and the precursor form of surfactant protein B (Pro-SFTPB), suggesting this panel of biomarkers might be highly useful for smoking-induced lung cancer risk assessment19. Here, CEACAM5 is linked to lung cancer.