However, one study of 45 EGFR-TKI-treated NSCLC patients with leptomeningeal metastases reported a higher detection rate of the T790M mutation (30.4% vs. 21.7%) and gene copy number variations (CNVs) such as MET (47.8% vs. 0) in CSF than in the plasma, indicating that genetic profiles in CSF may be different from those in plasma, and T790M status in the plasma or primary tumor cannot fully represent the mutation status in CSF (49). This evidence concerns the gene EGFR and non-small cell lung carcinoma.