SqCCs with EGFR mutation were resistant to EGFR-TKIs. (A) Kaplan–Meier curve shows that the median PFS after EGFR-TKI in lung SqCC patients carrying sensitizing EGFR mutation was 2.4 mo, similar to patients with wild-type EGFR (2.4 mo vs. 1.8 mo, P = 0.064). (B) Kaplan–Meier curve shows that the median overall survival after EGFR-TKI in lung SqCC patients carrying sensitizing EGFR mutation was 17.8 mo, similar to those with wild-type EGFR (17.8 mo vs. 12.5 mo, P = 0.511). (C) Cell viability analysis showed that lung SqCC cell lines (Beas/2b-19del, Beas/2b-21L858R, and SH416) presented stronger resistance to erlotinib than did a lung adenocarcinoma cell line with EGFR mutation (PC9). Viability at 72 h was calculated as the ratio of viable erlotinib-exposed cells to viable DMSO-treated cells.