Research on canine osteosarcoma lends itself well to comparative studies of osteosarcoma in humans because dogs develop spontaneous tumors which are similar to human cancers with the added benefit of frequently being more prevalent1. Osteosarcoma is diagnosed in more than 8000 dogs every year, and it affects mostly middle-aged to older dogs.2 The majority (75%) of canine osteosarcoma occurs in the appendicular skeleton.3 Osteosarcoma is diagnosed in 1-3 million humans every year, and is a disease primarily of those between 10 and 25 years old. Human osteosarcoma also occurs primarily in the appendicular skeleton, and like dogs, is most often found in the metaphyses of long bones. Pulmonary metastasis is the most common site of spread in dogs and humans, and is usually the cause of death in patients that have undergone standard of care therapy (surgical resection of tumor, chemotherapy).4 The reported median survival times for canine osteosarcoma have plateaued with no notable improvements in the last 20 years, despite attempts at various permutations of adjunctive chemotherapy.5,6,7 Targeting metastatic disease will be the key to improving survival in both canine and human osteosarcoma.