DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed advanced mesothelioma of the pleura

• Measurable disease

  • Unmeasurable pleural rinds allowed provided disease is evaluable by mesothelioma response criteria

  • The following are not considered measurable disease:

    • Pleural effusions
    • Positive bone scans
• Not a candidate for curative surgery
• No known or suspected brain metastases

PATIENT CHARACTERISTICS:

Age

• 18 and over

Performance status

• ECOG 0-1

Life expectancy

• Not specified

Hematopoietic

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

Hepatic

• Bilirubin ≤ 1.5 times upper limit of normal (ULN)
• AST and ALT ≤ 3 times ULN (5 times ULN if liver has tumor involvement)
• Albumin ≥ 2.5 g/dL

Renal

• Creatinine clearance ≥ 45 mL/min OR
• Creatinine ≤ 2.0 g/dL

Other

• Able to take folic acid and cyanocobalamin (vitamin B12)
• Willing and able to take dexamethasone
• Not obviously malnourished
• No weight loss > 10% within the past 6 weeks
• No active infection
• No other serious systemic disorder that would preclude study participation
• No other malignancy within the past 3 years except carcinoma in situ of the cervix or breast, other in situ malignancies, or adequately treated basal cell skin cancer
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception during and for 3 months after study participation

PRIOR CONCURRENT THERAPY:

Biologic therapy

• No prior intracavitary immunomodulators except for the purpose of pleurodesis

Chemotherapy

• No prior systemic chemotherapy for mesothelioma

Endocrine therapy

• Not specified

Radiotherapy

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

  • The lesion is clearly progressing after prior radiotherapy according to RECIST criteria
  • At least 4 weeks since prior radiotherapy

Surgery

• See Biologic therapy
• More than 2 weeks since prior pleurodesis

Other

• More than 4 weeks since prior investigational agents
• No prior intracavitary cytotoxic drugs except for the purpose of pleurodesis
• No aspirin or other nonsteroidal anti-inflammatory drugs for 2 days before, during, and for 2 days after each administration of pemetrexed disodium (5 days before, during, and 2 days after each administration of pemetrexed disodium for piroxicam, naproxen, diflunisal, or nabumetone)