DISEASE CHARACTERISTICS: Histologically proven malignant mesothelioma not amenable to potentially curative radiotherapy or surgery Epithelial, sarcomatoid, or mixed subtype Any site of origin allowed including, but not limited to, the following: Pleura Peritoneum Pericardium Tunica vaginalis Measurable disease At least one lesion accurately measured in at least one dimension Lesion at least 20 mm at largest diameter with conventional techniques or at least 10 mm with spiral CT scan The following are not considered measurable disease: Bone lesions Leptomeningeal disease Ascites Pleural/pericardial effusion Abdominal masses not confirmed and followed by imaging techniques Cystic lesions Tumor lesions located in a previously irradiated area

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0 or 1 Life expectancy: Not specified Hematopoietic: Granulocyte count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin no greater than 1.5 times upper limit of normal (ULN) SGOT no greater than 2.5 times ULN Renal: Creatinine no greater than 1.5 times ULN Other: Not pregnant or nursing Fertile patients must use effective contraception No active second malignancy except nonmelanomatous skin cancer Not considered an active second malignancy if: Therapy has been completed Less than 30% risk of relapse according to the physician No malabsorption syndrome

PRIOR CONCURRENT THERAPY: Biologic therapy: Concurrent epoetin alfa allowed Chemotherapy: No prior systemic cytotoxic chemotherapy for malignant mesothelioma Prior intrapleural cytotoxic or sclerosing agents (including bleomycin) allowed No other concurrent chemotherapy Endocrine therapy: No concurrent hormonal therapy except the following: Steroids administered for adrenal failure Hormonal therapy administered for nonmalignant conditions (e.g., insulin for diabetes) Intermittent use of dexamethasone as an antiemetic Radiotherapy: At least 4 weeks since prior radiotherapy Prior irradiation of symptomatic lesion allowed if there is other measurable disease outside the radiation port No concurrent radiotherapy Surgery: At least 2 weeks since prior major surgery Other: No concurrent leucovorin calcium or folinic acid