Osteosarcoma is the most common malignant bone tumor, with over 600 human patients diagnosed every year - mostly children, adolescents and young adults. While osteosarcoma accounts for only 2% of all pediatric cancers, it is responsible for nearly 10% of all pediatric cancer deaths, a statistic that has remained unchanged for 30 years. Osteosarcoma is also the most common bone tumor in dogs. Over 95% of dogs with osteosarcoma die of their disease, a statistic that has also remained unchanged over the past 25 years. Dr. Bernard Seguin of Colorado State University is trying to determine if his approach to using personalized treatments for each dog patient is effective at prolonging the dog's survival (rather than using a "one size fits all" treatment). Because dog and human osteosarcoma tumors share many similarities, the learnings from this study will have the potential to impact treatment for children as well.