EGFR and adenocarcinoma: A number of studies reported that elevated CEA was related to advanced disease (in terms of the p‐stage) and poor survival.41 CEA is an independent predictor for DFS and OS in EGFR wild‐type adenocarcinoma and the L858R substitution subgroup42 and a major prognostic predictor for EGFR mutation‐positive NSCLC with intracranial metastases when using brain radiotherapy and EGFR‐TKI.43 For the entire cohort, elevated CEA serum levels were a significant prognostic factor for a shorter survival time.