Background: Bone metastatic patients with osteosarcoma have a very poor prognosis. Targeted radiation therapy has been pursued as a valid alternative. The primary end point of this study was progression-free survival (PFS) at 4 months.
Patients and methods: Twenty-two osteosarcoma patients were treated with Samarium-153 ethylenediaminetetramethylene phosphonic acid (153Sm-EDTMP) at various dosages. Administered activities ranged from 150 (3 mCi/kg) to 1140 MBq/kg (30 mCi/kg). Autologous hematopoietic stem cell infusion was carried out on day 14 after the (153)Sm-EDTMP infusion.
Results: The median PFS was 61 days (18-436 days) and the median overall survival (OS) was 189 days (31-1175 days). PFS and OS for the entire patient population were 32% [95% confidence interval (CI) 16-50] and 76% (95% CI 52-89) at 4 months, respectively. No statistical differences emerged according to 153Sm-EDTMP administered or 24-h retained activity. One-month pain palliation was only observed in a minority of subjects and in none at 4 months.
Conclusions: Based on our series, the PFS is dramatically short even when higher activity of (153)Sm-EDTMP is administered. This would mean that, even at high level, 153Sm-EDTMP is itself ineffective against relapsed osteosarcoma or the residual activity is too low to be active on these particular subsets of patients.