EGFR and squamous cell carcinoma: It was 72.4 ± 23.3 pg/mL in patients with squamous cell carcinoma and 71.5 ± 25.4 pg/mL in patients with nonsquamous cell carcinoma, 70.3 ± 21.2 pg/mL in patients without brain metastasis and 76.5 ± 34.5 pg/mL in patients with brain metastasis, 72.2 ± 26.6 pg/mL in patients without pulmonary metastasis and 70.4 ± 20.2 pg/mL in patients with pulmonary metastasis, and 71.0 ± 25.4 pg/mL in patients with EGFR wild‐type and 69.4 ± 24.1 pg/mL in patients with an EGFR mutation; these values were not significantly different (P > 0.05).