Both pemetrexed and erlotinib are second-line treatment options for patients with advanced non-small cell lung cancer. It is controversial that whether it is necessary to detect epidermal growth factor receptor (EGFR) mutation status for the EGFR-targeted therapy after the failure of standard chemotherapy. The role of EGFR gene copy number as a predictive marker remains controversial. Therefore, we investigate the efficacy of erlotinib and pemetrexed as second-line therapy in treating in patients with EGFR wild-type and EGFR FISH-positive advanced lung adenocarcinoma.