DISEASE CHARACTERISTICS: Histologically proven osteosarcoma previously treated with standard chemotherapy agents (methotrexate, doxorubicin/cisplatin, ifosfamide) Active metastatic disease following chemotherapy At least 1 bidimensionally measurable lesion located in a nonirradiated area CT scan lesion at least 20 mm in at least 1 diameter Clinically measurable lesion at least 20 x 20 mm No symptomatic or known brain or leptomeningeal involvement