Overall, when we take into account the intratumoural heterogeneity and the different controversial results regarding the value of tissue tumour CAIX expression as a prognostic factor, we postulate that the detection of the soluble form of CAIX in plasma patients can be a more reliable prognostic factor of worse OS and DSS in patients with early-stage NSCLC. This evidence concerns the gene CA9 and non-small cell lung carcinoma.