Methotrexate, Trimetrexate Glucuronate, and Leucovorin in Treating Patients With Refractory or Recurrent Osteosarcoma

DISEASE CHARACTERISTICS: * Histologically confirmed malignant osteosarcoma * High-grade disease * Recurrent or refractory disease after prior standard chemotherapy comprising methotrexate, doxorubicin, cisplatin, and ifosfamide * No low-grade osteosarcoma * No parosteal or periosteal sarcoma * No osteosarcoma arising in premalignant bony lesions (e.g., Paget's disease) OR in a prior radiotherapy field * No symptomatic or known brain or leptomeningeal involvement PATIENT CHARACTERISTICS: Age * 1 to 35 Performance status * Karnofsky 70-100% (for patients \> 16 years of age) * Lansky 70-100% (for patients ≤ 16 years of age) Life expectancy * At least 3 months Hematopoietic * Absolute neutrophil count ≥ 1,000/mm\^3 * Platelet count ≥ 75,000/mm\^3 Hepatic * Bilirubin ≤ 1.5 times normal * AST and ALT ≤ 5 times normal * Albumin ≥ 2 g/dL * No clinically significant liver disease Renal * Creatinine ≤ 1.5 times normal OR * Creatinine clearance or radioisotope glomerular filtration rate ≥ lower limit of normal Cardiovascular * Shortening fraction ≥ 27% by echocardiogram OR * Ejection fraction ≥ 50% by gated radionuclide study * No congestive heart failure * No angina pectoris * No myocardial infarction within the past year * No uncontrolled arterial hypertension * No uncontrolled arrhythmias Other * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * No history of significant neurological or psychiatric disorder * No active infection * No symptomatic peripheral neuropathy ≥ grade 2 * No other serious illness or medical condition PRIOR CONCURRENT THERAPY: Biologic therapy * At least 7 days since prior biologic therapy * At least 6 months since prior allogeneic stem cell transplantation AND no evidence of active graft-versus-host disease * No concurrent sargramostim (GM-CSF) Chemotherapy * See Disease Characteristics * More than 2 weeks since prior myelosuppressive chemotherapy (4 weeks for nitrosoureas) Endocrine therapy * Not specified Radiotherapy * See Disease Characteristics * At least 2 weeks since prior local palliative radiotherapy (small port) * At least 6 months since prior craniospinal radiotherapy * At least 6 months since prior radiotherapy to ≥ 50% of the pelvis * At least 6 weeks since prior substantial radiotherapy to the bone marrow Surgery * Not specified Other * Recovered from prior therapy * More than 30 days since prior and no other concurrent investigational drugs * More than 30 days since prior and no concurrent participation in another clinical trial * No concurrent medications that may interact with study drugs