Patients harboring complex (common mutations co-existing with uncommon mutations), or common (comparison cohort) EGFR mutations, who were treated with dacomitinib, were retrospectively evaluated in the Chinese National Cancer Center and the China PLA hospital between August 2019 and August 2021....In total, 72 patients with NSCLC harboring complex (C+U group, n=18) or common (C group, n=54) EGFR mutations and being treated with dacomitinib were enrolled. In the C+U group, 16 cases (88.9%) harbored L858R mutations co-existing with uncommon mutations located from exon 18 to exon 25 of EGFR (mostly E709X), and two cases harbored exon 19 deletion co-existing with G724S or K754E....the stratified analysis found worse PFS in the C+U group than that observed in the C group when receiving 1st and ≥3rd line dacomitinib treatment, while its OS was worse than that of group C when receiving ≥3rd line treatment.