EGFR and lung adenocarcinoma: The aim of this study was to investigate the clinical efficacy and determine the prognostic value of Epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKIs) alone versus EGFR-TKIs plus chemotherapy for the treatment of advanced lung adenocarcinoma with EGFR Exon 19 Deletion(19Del), Exon 21 L858R (L858R) mutation.