Phase II study of ecteinascidin 743 in heavily pretreated patients with recurrent osteosarcoma

BACKGROUND. Recurrent osteosarcoma is a drug-resistant disease with a dismal prognosis. The objective of this Phase II study was to evaluate the activity of ecteinascidin 743 (ET-743) as a salvage therapy in these patients. METHODS. Patients with recurrent osteosarcoma who had received standard chemotherapeutic agents were eligible. ET-743 was administered at a dose of 1500 μg/m² as a 24-hour infusion every 3 weeks. Pharmacokinetic studies were performed during the first cycle. RESULTS. Twenty-five patients were enrolled, 23 of whom were assessable for response (median age of 18 years; range, 12-67 years). The median number of previous chemotherapeutic agents was five (range, three to eight previous agents). Sixty-one cycles were administered (median number of cycles per patient was 2; range, 1-9 cycles per patient). Three patients (12%) achieved minor responses (49% 36% and 25%, respectively). Fifteen patients (60%) developed a transient elevation of hepatic transaminases (Grade 3 or 4 [according to the National Cancer Institute Common Toxicity Criteria]), which was not cumulative. Grade 3 or 4 neutropenia and thrombocytopenia were observed in 12 patients (48%) and 6 patients (24%), respectively. The mean area under the curve (AUC) in 4 patients experiencing Grade 4 toxicity (76.4 ± 29.3 ng × hr/mL) was significantly greater (P = 0.034) than that in those for whom the most severe toxicity was Grade 3 (39.5 ± 17.2 ng × hr/mL [n = 12]) or Grade 1-2 (52.6 ± 15.6 ng × hr/mL [n = 5]). There were no other significant correlations found between pharmacokinetic variables and patient characteristics, toxicity, or therapeutic response. CONCLUSIONS. ET-743 was found to be well tolerated in heavily pretreated osteosarcoma patients but had limited antitumor activity as a single agent. The combination of ET-743 with cisplatin or doxorubicin should be considered.