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