Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed malignant pleural or peritoneal mesothelioma of 1 of the
following subtypes:

- Epithelial

- Sarcomatoid

- Mixed subtype

- Disease not amenable to curative surgery

- Measurable disease

- At least 1 measurable lesion at least 20 mm by conventional techniques or at
least 10 mm by spiral CT scan

- At least 1 level on lesion scan must have 1 pleural rind measurement at least 15
mm

- If there is only 1 measurable lesion, the neoplastic nature must be
histologically confirmed

- Clinically detected lesions are only considered measurable if superficial (e.g.,
skin nodules and palpable lymph nodes)

- The following are not considered measurable disease:

- Pleural effusions

- Positive bone scans

- No known or suspected brain metastases

PATIENT CHARACTERISTICS:

Age

- 18 and over

Performance status

- ECOG 0-2

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)

- Alkaline phosphatase no greater than 3 times ULN*

- ALT and AST no greater than 3 times ULN*

- Albumin at least 2.5 g/dL NOTE: *No greater than 5 times ULN in the case of liver
involvement by tumor

Renal

- Creatinine clearance at least 45 mL/min

Other

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception during and for 3 months after study
participation

- No active infection

- No concurrent serious systemic disorders (including oncologic emergencies) that would
preclude study participation

- No other currently active malignancy except nonmelanoma skin cancer or carcinoma in
situ of the cervix (patients with previously treated malignancy are eligible if at
less than 30% risk of relapse)

- Able to tolerate folic acid or cyanocobalamin administration

PRIOR CONCURRENT THERAPY:

Biologic therapy

- No prior intracavitary immunomodulators, unless given for pleurodesis

- No filgrastim (G-CSF) within 24 hours of study chemotherapy administration

- No concurrent immunotherapy

- No concurrent routine colony-stimulating factor therapy

- No concurrent stimulators of thrombopoiesis

Chemotherapy

- No prior systemic chemotherapy

- No other concurrent chemotherapy

Endocrine therapy

- No concurrent hormonal therapy for cancer

Radiotherapy

- Prior radiotherapy to the target lesion allowed provided the lesion has clearly
progressed

- At least 4 weeks since prior radiotherapy

- No concurrent non-palliative radiotherapy

Surgery

- No concurrent surgery for cancer

Other

- At least 2 weeks since prior pleurodesis

- No prior intracavitary cytotoxic drugs, unless given for pleurodesis

- More than 4 weeks since prior investigational agents

- No aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) within 2 days of
pemetrexed disodium administration

- No long-acting NSAIDs (e.g., naproxen, piroxicam, diflunisal, nabumetone,
rofecoxib, or celecoxib) within 5 days of pemetrexed disodium administration

- No other concurrent experimental medications (except thymidine)