Hence this study aimed to systematically evaluate the frequency of discordance in EGFR mutation between primary tumor and paired distant metastases among patients with NSCLC in the published peer-reviewed articles and perform a meta-analysis to assess for any differences by metastatic sites, mutation status of primary tumor, methods of testing and timing of metastasis relative to the diagnosis of primary tumor. This evidence concerns the gene EGFR and non-small cell lung carcinoma.