EGFR and lung cancer: To further confirm whether EGFR-TKI treatment affects CEA expression and metastasis in patients, we divided EGFR-mutant lung cancer patients into four groups based on their CEAIn (CEAIn < 5 ng/mL or CEAIn ≥ 5 ng/mL) and CEAPd levels (CEAPd < 5 ng/mL or CEAPd ≥ 5 ng/mL).