Gefitinib in Treating Patients With Previously Untreated Stage IIIB or Stage IV Non-Small Cell Lung Cancer

RATIONALE: Gefitinib may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. PURPOSE: This phase II trial is studying how well gefitinib works in treating patients with previously untreated stage IIIB or stage IV non-small cell lung cancer.

OBJECTIVES: Primary * Determine the objective tumor response rate in patients with previously untreated stage IIIB or IV non-small cell lung cancer with somatic activating mutations in the TK region of the epidermal growth factor receptor (EGFR) gene treated with gefitinib. Secondary * Determine response duration, progression-free survival, and overall survival of patients treated with this drug. * Determine the safety of this drug in these patients. * Compare the ability of various somatic activating mutations in the TK region of the EGFR gene to predict response in patients treated with this drug. * Compare the ability of various somatic activating mutations in the TK region of the EGFR gene to predict toxicity of this drug in these patients. * Define a molecular profile in patients who initially respond to treatment with this drug but subsequently progress on therapy. * Determine the significance of germline polymorphisms of the EGFR gene, somatic amplification of the EGFR gene, and other molecular factors for their association with clinical outcome parameters in these patients. OUTLINE: This is an open-label study. Patients receive oral gefitinib once daily on days 1-28. Courses repeat every 28 days in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed every 2 months. PROJECTED ACCRUAL: A total of 30 patients will be accrued for this study.