Prolonged response to sorafenib in a patient with refractory metastatic osteosarcoma and a somatic PDGFRA D846V mutation.

Outcome for patients with metastatic or recurrent/refractory osteosarcoma remains poor. Responses to sorafenib, a multikinase inhibitor, have been seen in recurrent/refractory osteosarcoma, although specific biomarkers of response have not been described. We report a partial response in a 7-year-old with refractory osteosarcoma treated with sorafenib 200 mg twice daily. Toxicities included Common Terminology Criteria for Adverse Events Grade 2 skin toxicities and growth suppression. After 51 months of therapy, he suffered a recurrence. Tumor sequencing later revealed a PDGFRA D846V mutation that was not identified in the relapse specimen. This case demonstrates prolonged partial response to sorafenib and provides a potential biomarker for response.