In the present study, we investigated spatial tumor heterogeneity using autopsy specimens from EGFR mutated NSCLC patients, showing primary resistance to erlotinib plus ramucirumab....the AXL expression levels were likely to negatively correlate with the efficacy of erlotinib plus ramucirumab therapy. The analysis of patient-derived cell lines, established from left pleural effusion before initiation of the treatment, showed that the combination of EGFR-TKIs and an AXL inhibitor remarkably inhibited cell viability compared with EGFR-TKI monotherapy or combination with ramucirumab.