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

DISEASE CHARACTERISTICS:

* Pathologically confirmed non-small cell lung cancer (NSCLC)

  * No squamous cell histology
* Stage IIIB (with pleural effusion) or stage IV disease
* Must meet ≥ 1 of the following criteria:

  * Female
  * Adenocarcinoma tumor histology
  * No history of smoking, defined as smoking \< 100 cigarettes (5 standard packs of cigarettes) in a lifetime, \< 20 oz of pipe tobacco in a lifetime, OR \< 100 cigars in a lifetime
  * Asian/Pacific Rim ethnicity, defined as Japanese, Chinese, Korean, or other Asian/Pacific Rim ethnicity
* Must have activating mutations in the TK region of the epidermal growth factor receptor (EGFR) gene
* Measurable disease
* No symptomatic or newly diagnosed CNS metastases that have not been definitively treated with radiotherapy and/or surgery

  * History of CNS metastases or cord compression allowed if definitively treated and clinically stable

PATIENT CHARACTERISTICS:

* See Disease Characteristics
* ECOG performance status 0-2
* Life expectancy ≥ 12 weeks
* Absolute neutrophil count ≥ 2,000/mm³
* Platelet count ≥ 100,000/mm³
* Bilirubin ≤ 1.25 times upper limit of normal (ULN)
* ALT and AST ≤ 2.5 times ULN (5 times ULN if liver has tumor involvement)
* Creatinine ≤ 1.5 times ULN OR creatinine clearance ≥ 60 mL/min
* Not pregnant or nursing
* Negative pregnancy test
* Fertile patients must use effective contraception
* No known severe hypersensitivity to gefitinib or any other component of gefitinib tablets
* No evidence of clinically active interstitial lung disease

  * Patients with chronic, stable radiographic changes who are asymptomatic are eligible
* No other concurrent malignancy or malignancy diagnosed within the past 5 years except for basal cell carcinoma of the skin or cervical cancer in situ
* No concurrent severe or uncontrolled systemic disorder
* No evidence of any other significant clinical disorder or laboratory finding that, in the opinion of the investigator, would preclude study participation
* Able to tolerate protocol treatment, in the opinion of the investigator

PRIOR CONCURRENT THERAPY:

* See Disease Characteristics
* No prior systemic chemotherapy, biological therapy, immunotherapy, or hormonal therapy for NSCLC, including adjuvant and neoadjuvant treatment
* No prior radiotherapy to the target lesion

  * Prior radiotherapy to bony disease or CNS disease allowed
* At least 2 weeks since prior radiotherapy and recovered
* More than 30 days since prior non-FDA approved or investigational agents
* No prior EGFR antagonists
* At least 2 weeks since prior and no concurrent phenytoin, carbamazepine, rifampin, barbiturates, or Hypericum perforatum (St. John's wort)
* No concurrent chemotherapy, immunotherapy, hormonal therapy, nonpalliative radiotherapy, surgery for cancer, or other experimental medications
* No other concurrent specific antitumor therapy