19 of the remained studies were then further excluded: 8 studies focused on the correlation between pretreatment T790M and prognosis of EGFR-mutant advanced NSCLC patients, 5 of the studies were based on assay methods, 4 studies evaluated different index such as response rate and 5-year survival, 2 studies had insufficient/invalid data, and 3 were excluded for evaluating T790M status through plasma DNA. Here, EGFR is linked to non-small cell lung carcinoma.