The investigators will examine efficacy and toxicity of gefitinib in Korean patients with EGFR wild tumors diagnosed with direct sequence test.

Inclusion Criteria:

• Pathologically proven NSCLC

• Ineligibile for curative treatment (namely, stage IIIb or IV)

• History of one to three prior systemic chemotherapy tumors without active EGFR mutations (exon 19 deletion, L858R mutation in exon 21)

• At least one lesion that was unidimensionally measurable by computed tomography (by RECIST 1.1)

• 18 years old or older

• Performance status ECOG 0-2

• Adequate organ function as evidenced by the following:

  • Absolute neutrophil count > 1.0 x 109/L
  • Platelets > 75 x 109/L
  • Total bilirubin ≤ 1.5 UNL
  • AST and/or ALT < 5 UNL
  • Creatinine clearance ≥ 45mL/min

Exclusion Criteria:

• Previous EGFR TKI therapy history
• Systemic anticancer therapy within the previous 3 weeks
• Other invasive malignancy within the past 2 years except non-melanoma skin cancer, in situ cervix cancer, or papillary thyroid cancer
• Other concurrent illness that would preclude study participation (severe heart disease)
• Other concurrent physical condition (e.g., infectious disease) that would preclude study participation
• Pregnant or nursing