The experience of radiotherapy (RT) in the local treatment of osteosarcoma (OS) is limited. Data of 100 patients with RT for OS from the international COSS-Registry (1980–2007) were analysed. Survival and local control rates at five years were calculated. Univariate and multivariate analyses were performed.

The COSS-registry includes 3500 patients with histo-logically proven OS. A total of 175 patients were irradiated over the period of 1980 to 2007, 100 patients were eligible. Median age was 18 (3–66) years. Indication for RT was a primary tumor in 66, a local recurrence in 11 and metastases in 23 patients. 94 Patients got external photontherapy, 2 pats. protontherapy, 2 pats. neutrontherapy, and 2 pats. intraoperative RT. Seventeen patients received a samarium-153-EDTMP therapy. Median dose for external RT was 55.8 Gy All patients were treated with chemotherapy in accordance to different COSS-protocols.

Median follow-up is 1.5 (0.2–23) years. Overall survival rates at 5 years for the whole group, for treatment of primary tumours, local recurrence, and metastases are 36 %, 55%, 15%, and 0% respectively. Local control rate for combined surgery and RT is significantly better than for RT alone (48% vs. 22%, p=0.002). Local control for treatment of primary tumours, local recurrence, and metastases are 40%, 17%, and 0% respectively. Prognostic factors for survival are indication for RT, RT plus surgery vs. RT alone and localisation. Prognostic factors for local control are indication for RT, and RT plus surgery vs. RT alone.

Radiotherapy is an important option for local treatment of unresectable OS, after intralesional resection, or symptomatic metastases. Survival prognosis of these patients is poor. Combination of surgery, radiotherapy, and chemotherapy can be curative. Prognostic factors were identified.