Bone metastasis in extremity soft tissue sarcomas: risk factors and survival analysis using the SEER registry.

High tumor grade, deep location to fascia and regional lymph node metastasis are significant risk factors for skeletal metastasis at diagnosis of an extremity STS. While neither systemic chemotherapy nor radiotherapy of the primary sarcoma has a significant influence on survival in the presence of bone metastasis, radical resection of the primary STS is associated with increased survival.