Zhao et al. [43] analyzed paired plasma and cerebrospinal fluid (CSF) samples from seven NSCLC patients with CNS metastases after failure with first-generation EGFR-TKIs and found that all harbored EGFR-TKI-sensitive mutations in CSF but that only one harbored T790M mutation in CSF. Here, EGFR is linked to non-small cell lung carcinoma.