There was no significant correlation between EGFR mutation in peripheral blood ctDNA and sex, age, ethnicity and ECOG score (p>0.05), and the EGFR mutation rate was increased in patients with adenocarcinoma compared with that in patients with squamous carcinoma, and in non-smoking patients compared with that in smoking patients, with statistically significant differences(p<0.05). Here, EGFR is linked to adenocarcinoma.