EGFR and lung cancer: Afatinib, a 2nd-generation EGFR-TKI covalently linked in a tyrosine kinase domain of EGFR, is known to show a high antitumor effect by inhibiting phosphorylation irreversibly, and there was a report that showed a proliferation inhibitory effect on lung cancer cell strain that had T790M mutation[2]; therefore, therapeutic effects in patients with T790M mutation-positive lung cancer (T790M-positive patients) were initially expected.