DISEASE CHARACTERISTICS:

• Histologic or cytologic diagnosis of non-small cell lung cancer (NSCLC), meeting 1 of the following staging criteria:

  • Stage IIIA disease, meeting all of the following criteria:

    • Mediastinal lymph node involvement

      • Greater than one mediastinal lymph node enlarged on CT scan, confirmed by positron emission tomography (PET) scan
    • Paralyzed left vocal cord with separate lung primary distinct from the aorto-pulmonary lymph nodes on the CT scan

  • Stage IIIB disease, meeting all of the following criteria:

    • N3 lymph node involvement

      • Enlarged N3 lymph nodes on CT scan confirmed by PET scan

        • Lymph node involvement may not extend to cervical lymph nodes other than supraclavicular lymph nodes
    • Right-sided primary tumor with left vocal cord paralysis
    • Evidence of tumor extension into the mediastinum and/or mediastinal structures by mediastinoscopy, bronchoscopy, or CT scan
    • No evidence of malignant pleural effusion unless effusion is only evident on CT scan
    • No more than 1 parenchymal lesions on the same or opposite sides of the lung
• No brain metastases by CT scan or MRI

PATIENT CHARACTERISTICS:

• SWOG performance status 0 or 1
• Platelet count ≥ 100,000/mm³
• Absolute neutrophil count ≥ 1,500/mm³
• Creatinine ≤ 1.5 times upper limit of normal (ULN)
• Creatinine clearance ≥ 45 mL/min
• Bilirubin normal
• Transaminases (SGOT and/or SGPT) ≤ 1.5 times ULN
• Alkaline phosphatase ≤ 2.5 times ULN
• Total lung volume (i.e., right and left lung minus the gross tumor volume) receiving greater than 20 Gy of radiation ≤ 40%
• FEV_1 ≥ 70% of predicted
• DLCO ≥ 50 mL/min

• No other concurrent malignancy

  • Prior malignancy allowed provided it is in clinical control and is not likely to impact clinical outcome in the opinion of the treating physician
• No peripheral neuropathy ≥ grade 2

• No serious medical illness, including, but not limited to, any of the following:

  • Uncontrolled congestive heart failure
  • Uncontrolled angina
  • Myocardial infarction
  • Cerebrovascular event within the past 6 months
  • History of chronic active hepatitis
  • History of HIV infection
  • Active bacterial infection
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• Must be willing and able to take folic acid, cyanocobalamin (vitamin B12), or dexamethasone

PRIOR CONCURRENT THERAPY:

• No prior chemotherapy or radiotherapy for NSCLC
• No concurrent participation in another therapeutic investigational study
• Concurrent ibuprofen (400 mg four times daily) allowed during pemetrexed disodium administration provided the patient has normal renal function

• No concurrent aspirin or other nonsteroidal antiinflammatory drugs (NSAIDs) 2 days before, during, and for 2 days after pemetrexed disodium administration

  • Patients on long-acting NSAIDs (e.g. naproxen sodium, diflunisal, nabumetone, or celecoxib) must be willing or able to discontinue usage 5 days prior to, during, and for 2 days after pemetrexed disodium administration