Among the 9 patients with EGFR exon 21 mutated NSCLC in this study, 8 patients harboring L858R mutation...They all received low dose of dacomitinib as initial treatment. The ORR was 77.8% and DCR was 100%....Our study showed that dacomitinib (15 mg, once a day) may be also effective for patients harboring EGFR exon 21 mutated NSCLC...