Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically or cytologically confirmed locally advanced or metastatic non-small
cell lung cancer

- Stage IIIB disease that is ineligible for combined modality therapy OR

- Stage IV disease

- Measurable disease

- No clinically detectable (by physical exam) third-space fluid collection (e.g.,
ascites or pleural effusions) that cannot be controlled by drainage or other
procedures

- No brain metastases (even if treated)

PATIENT CHARACTERISTICS:

Age:

- 18 and over

Performance status:

- ECOG 0-1

Life expectancy:

- At least 12 weeks

Hematopoietic:

- Absolute neutrophil count at least 1,500/mm^3

- Platelet count at least 100,000/mm^3

- Hemoglobin at least 9 g/dL

Hepatic:

- Bilirubin no greater than 1.5 times upper limit of normal (ULN)

- AST and ALT no greater than 3 times ULN (5 times ULN if liver metastases present)

- Alkaline phosphatase no greater than 3 times ULN (5 times ULN if liver metastases
present)

Renal:

- Creatinine clearance at least 45 mL/min

Other:

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- Able to take folic acid or cyanocobalamin (vitamin B12) supplementation

- No uncontrolled infection

- No concurrent chronic debilitating disease

- No weight loss of 10% or more within the past 6 weeks

- No other prior malignancy within the past 5 years except adequately treated basal
cell or squamous cell skin cancer or noninvasive carcinoma

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- No prior biologic or genetic therapy for lung cancer

- No concurrent immunomodulating agents

Chemotherapy:

- No prior chemotherapy for lung cancer

Endocrine therapy:

- Not specified

Radiotherapy:

- At least 4 weeks since prior radiotherapy to a different site and recovered

- No prior radiotherapy to 25% or more of bone marrow

- No prior radiotherapy to whole pelvis

- No prior radiotherapy for primary disease

- No concurrent radiotherapy

Surgery:

- More than 4 weeks since prior major surgery

Other:

- No aspirin or nonsteroidal anti-inflammatory agents 2 days before, during, and for 2
days after pemetrexed disodium administration (5 days for long-acting agents such as
piroxicam, naproxen, diflunisal, or nabumetone)

- No other concurrent cytostatic or cytotoxic therapy