EGFR and non-small cell lung carcinoma: Namely, while earlier investigations did not observe clear relationship between EGFR expression and clinical outcomes for the NSCLC patients treated with TKI [53, 54], succeeding studies reported significant association of both high EGFR gene copy number (due to gene amplification or chromosome polysomy) and high protein expression with better response to gefitinib or erlotinib [55–57].