EGFR and Pleural effusion: Among the thirteen patients with intracranial progressions only, two patients were lost to follow-up, eight had genetic reassessment, of which acquired EGFR T790M-positive status was confirmed by blood sample in one patient and the same EGFR mutations remained detectable in the other seven patients, with blood samples used in five patients, cerebrospinal fluid sample in one patient and pleural effusion sample in one patient.