In this analysis, we included EGFR-mutant lung adenocarcinoma patients who received EGFR tyrosine kinase inhibitor (TKI) therapy, had a pre-TKI sample available (CSF, N = 7; tumor biopsy, N = 1, pleural effusion, N = 1), and had available post-TKI therapy CSF and plasma samples, collected within two weeks of each other with no intervening treatment. This evidence concerns the gene EGFR and Pleural effusion.