DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed non-small cell lung cancer (NSCLC), meeting 1 of the following stage criteria:

  • Stage IIIA or IIIB disease

    • Progressive disease

  • Stage IV disease

    • Failed 1 prior platinum-based chemotherapy regimen, including adjuvant therapy

• Measurable or evaluable disease, as defined by 1 of the following criteria:

  • At least 1 unidimensionally measurable lesion ≥ 20 mm by conventional techniques OR > 10 mm by spiral CT scan
  • Lesions apparent on CT scan that do not meet the criterion for measurability
• Brain metastases allowed provided patient has received definitive therapy for metastases, is asymptomatic, and has extra-CNS metastases

PATIENT CHARACTERISTICS:

Age

• 18 and over

Performance status

• ECOG 0-1

Life expectancy

• More than 12 weeks

Hematopoietic

• WBC ≥ 3,000/mm^3
• Absolute neutrophil count ≥ 1,500/mm^3
• Platelet count ≥ 100,000/mm^3

Hepatic

• AST and ALT ≤ 1.5 times normal
• Alkaline phosphatase < 1.5 times normal
• Bilirubin ≤ 1.3 mg/dL

Renal

• Creatinine ≤ 1.6 mg/dL OR
• Creatinine clearance ≥ 50 mL/min

Cardiovascular

• No unstable angina
• No congestive heart failure
• No myocardial infarction within the past 3 months
• No life-threatening ventricular arrhythmia requiring maintenance therapy

Other

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective barrier contraception during and for 3 months after completion of study treatment
• No uncontrolled seizure disorder
• No uncontrolled diabetes mellitus
• No active infection requiring systemic therapy
• No other malignancy within the past 5 years except nonmelanoma skin cancer or carcinoma in situ of the cervix
• No other unstable or serious condition

PRIOR CONCURRENT THERAPY:

Biologic therapy

• Not specified

Chemotherapy

• See Disease Characteristics
• At least 3 weeks since prior chemotherapy
• Prior irinotecan allowed
• No prior gemcitabine
• No more than 1 prior chemotherapy regimen for NSCLC, excluding gefitinib
• No other concurrent chemotherapy

Endocrine therapy

• Not specified

Radiotherapy

• At least 4 weeks since prior radiotherapy
• No concurrent radiotherapy

Surgery

• Not specified

Other

• More than 1 month since prior participation in another clinical trial using an investigational agent
• No other concurrent investigational agents