Pemetrexed Disodium Plus Gemcitabine in Treating Patients With Locally Advanced or Metastatic Non-Small Cell Lung Cancer

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