As a continuity of our prophase study, the current study explored the impact of chemotherapy on both EGFR activating mutations,especially, assessed variations in mutation quantity in EGFR exon 19 and clinical significance, and further investigated potential alterations of EGFR-TKI resistance-related genes, such as T790M, KRAS and c-MET aberrances using the same cohort of matched tumor tissue samples of pre- and post- Neoadj-Chemo from stage IIb-IIIb NSCLC patients. The gene discussed is EGFR; the disease is neoplasm.