EGFR and neoplasm: The first-generation EGFR-TKI erlotinib, as an EGFR/ErbB1-selective inhibitor with a reversible and non-covalent binding property [5], likely possesses an anti-tumor activity more vulnerable to intra-tumoral concentration variation as a result of the impaired drug delivery through a pathologic vasculature of tumor stroma [6,7].