DISEASE CHARACTERISTICS:

• Histologically and/or cytologically confirmed non-small cell lung cancer (NSCLC)

  • Stage IIIB disease with pleural or pericardial effusion
  • Stage IV disease
  • Unresectable or recurrent disease
• No mixed forms with small cell lung cancer
• Must have received 1 prior first-line combination chemotherapy (platinum- or non-platinum-based) regimen
• Measurable disease, defined as ≥ 1 unidimensionally measurable lesion ≥ 20 mm by conventional techniques OR ≥ 10 mm by spiral CT scan
• No symptomatic, uncontrolled (by corticosteroids) brain metastasis
• No leptomeningeal metastasis

PATIENT CHARACTERISTICS:

Age

• 18 and over

Performance status

• ECOG 0-1

Life expectancy

• Not specified

Hematopoietic

• Absolute granulocyte count ≥ 1,500/mm^3
• Platelet count ≥ 100,000/mm^3
• Hemoglobin ≥ 9.0 g/dL

Hepatic

• AST and ALT ≤ 2.5 times upper limit of normal (ULN) (5 times ULN if due to liver metastasis)
• Bilirubin ≤ 1.5 times ULN

Renal

• Creatinine clearance ≥ 60 mL/min

Cardiovascular

• No myocardial infarction within the past 6 months
• No severe or unstable angina
• No New York Heart Association class III or IV congestive heart failure

Other

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception during and for 30 days after study participation
• No other active malignancy
• No psychiatric disorder or condition, severe acute or chronic medical condition, or laboratory abnormality that would preclude study compliance
• No known HIV- or AIDS-related illness
• Able to take oral medication
• No known neuropathy ≥ grade 2
• No chronic nausea, vomiting, and/or diarrhea

PRIOR CONCURRENT THERAPY:

Biologic therapy

• More than 3 weeks since prior immunotherapy or biologic therapy
• No concurrent immunotherapy
• No concurrent biologic response modifiers

Chemotherapy

• See Disease Characteristics
• No prior first-line treatment with S-1 for NSCLC
• More than 3 weeks since prior chemotherapy (6 weeks for nitrosoureas or mitomycin)
• No other concurrent chemotherapy
• No other fluoropyrimidine-group antineoplastic agent within 7 days after the last dose of S-1

Endocrine therapy

• See Disease Characteristics
• At least 3 weeks since prior hormonal therapy
• No concurrent endocrine therapy

Radiotherapy

• More than 2 weeks since prior radiotherapy

• Prior radiotherapy to a target lesion allowed provided the following criteria are met:

  • No radiotherapy within the past 3 months
  • Evidence of progressive disease after radiotherapy
  • Target lesion is not the only site of measurable disease
• No concurrent radiotherapy

Surgery

• Not specified

Other

• More than 3 weeks since prior therapy for NSCLC
• At least 30 days since prior investigational agents
• No prior second-line therapy for NSCLC
• No other concurrent participation in another clinical trial
• No other concurrent investigational agent

• No concurrent administration of any of the following:

  • Sorivudine
  • Uracil
  • Cimetidine
  • Leucovorin calcium
  • Dipyridamole
  • Allopurinol
  • Phenytoin
  • Flucytosine
• No other concurrent drugs that may interact with S-1
• No other concurrent anticancer therapy
• No flucytosine within 7 days after the last dose of S-1