RATIONALE: Some tumors need growth factors produced by the body's white blood cells to keep growing. ZD 1839 may interfere with the growth factor and stop the tumor from growing. Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. It is not yet known whether chemotherapy is more effective with or without ZD 1839 for non-small cell lung cancer.

PURPOSE: Randomized phase III trial to compare the effectiveness of combination chemotherapy with or without ZD 1839 in treating patients who have stage IIIB or stage IV non-small cell lung cancer.

OBJECTIVES: I. Compare the 1 year survival rate, time to worsening of disease related symptoms, and progression free survival in chemotherapy naive patients with stage IIIB or IV non-small cell lung cancer treated with one of two doses of ZD 1839 or placebo combined with gemcitabine and cisplatin.

OUTLINE: This is a randomized, double blind, placebo controlled, multicenter study. Patients are randomized to one of three treatment arms. Patients receive gemcitabine and cisplatin combined with lower dose oral ZD 1839 (arm I), higher dose oral ZD 1839 (arm II), or placebo (arm III).

PROJECTED ACCRUAL: A total of 1,029 patients (343 per arm) will be accrued for this study.

• Drug: cisplatin
• Drug: gefitinib
• Drug: gemcitabine hydrochloride

DISEASE CHARACTERISTICS: Histologically proven non-small cell lung cancer Stage III disease that is not curable with surgery or radiotherapy OR Stage IV disease Chemotherapy naive

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: 0-2 Life expectancy: Not specified Hematopoietic: Absolute neutrophil count at least 2,000/mm3 WBC at least 4,000/mm3 Hepatic: ALT and AST less than 2.5 times upper limit of normal (ULN) (less than 5 times ULN if liver metastasis present) Bilirubin less than 1.25 times ULN Renal: Creatinine less than 1.5 times ULN Creatinine clearance greater than 60 mL/min Cardiovascular: No evidence of severe or uncontrolled cardiovascular disease Pulmonary: No evidence of severe or uncontrolled pulmonary disease

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: See Disease Characteristics Endocrine therapy: No concurrent systemic endocrine therapy that is known to have an effect on non-small cell lung cancer Radiotherapy: See Disease Characteristics Prior localized irradiation allowed Surgery: See Disease Characteristics Prior surgery allowed Other: No concurrent drugs with known significant cytochrome P450 3A4 inhibitory effects (e.g., ketoconazole, itraconazole, troleandomycin, erythromycin, diltiazem, verapamil)