Raltitrexed in Treating Patients With Malignant Mesothelioma That Cannot Be Surgically Removed

DISEASE CHARACTERISTICS: Histologically proven inoperable malignant mesothelioma All tumor stages eligible At least 1 target lesion with measurable disease in at least 1 dimension (20 cm or more with conventional techniques OR 10 cm or more with spiral CT scans) Outside irradiated field Prior surgery allowed if evidence of disease progression thereafter No signs or symptoms of CNS metastases PATIENT CHARACTERISTICS: Age: Over 18 Performance status: ZUBROD/ECOG/WHO 0-2 (after palliative measures such as pleural drainage) Life expectancy: Not specified Hematopoietic: Hemoglobin at least 10.0 g/dL WBC at least 4,000/mm3 Absolute neutrophil count at least 2,000/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin less than 1.46 mg/dL Albumin at least 3.0 g/dL ALT and AST less than 2.5 times upper limit of normal (ULN) (less than 5 times ULN if liver involvement) Renal: Creatinine less than 1.69 mg/dL Creatinine clearance at least 65 mL/min Other: No other malignancies (including melanoma, hypernephroma, or breast carcinoma) within the past 5 years except basal cell or squamous cell skin cancer or carcinoma in situ of the cervix Not pregnant or nursing Fertile patients must use effective contraception No uncontrolled infection No psychologic, familial, sociologic, or geographic condition that could interfere with compliance PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent anticancer immunotherapy before first disease progression Chemotherapy: No prior systemic or intracavitary cytotoxic drugs No concurrent intrapleural or other systemic cytotoxic drugs Endocrine therapy: No concurrent anticancer hormonal agents (except corticosteroids) before first disease progression Radiotherapy: See Disease Characteristics Concurrent palliative radiotherapy allowed for painful lesions, needle tracts, or surgical scars or prevention of metastases along biopsy tracks At least 4 weeks since prior radiotherapy No prior radiotherapy to sole indicator lesion unless lesion is clearly progressive Surgery: See Disease Characteristics Prior pleurodesis allowed except with cytotoxic drugs (e.g., bleomycin) Concurrent pleurodesis with noncytotoxic drugs allowed Other: At least 1 month since other prior investigational agent No other concurrent anticancer agents before first disease progression