Combining Therapies to Improve Osteosarcoma Treatment

SUMMARY: Researchers will study whether a combination of oral medication and new tumor vaccine provide survival benefit for dogs diagnosed with osteosarcoma.

THE PROBLEM: Osteosarcoma (OS) is the most common bone cancer in dogs, affecting the long bones of mostly large and giant breeds of dog. The standard treatment for OS is amputation of the limb followed by a course of chemotherapy. Despite this treatment, half of dogs develop spread of their cancer at 6 months after amputation, and half of dogs do not live beyond 300 days; only 25% of dogs live to 2 years. This is because once OS has spread, it is extremely resistant to treatment, with less than 10% of dogs responding to any type of therapy. No improvements for the care of dogs with OS have happened in over 30 years, despite many studies using combinations of chemotherapy and immune-based approaches. 

THE PROJECT: It is now known that OS cells prevent the immune system from killing them by creating an environment around the tumor that blocks the ability of immune cells to work. To address this, the research team has combined three oral medications that help to activate immune cells in the tumor and restore immune function. In a recent study of dogs with OS spread to the lungs, 30% of dogs responded to the treatment, with one dog cured of disease. Also, another 40% of dogs had their disease stop growing, more than doubling survival time from an average of 60-90 days after the diagnosis of OS spread to over 150 days. The purpose of this study is to improve on this oral therapy by adding a new OS tumor vaccine. The vaccine uses a special formula to stimulate the immune system. This vaccine formula was found to be safe and was able to partially shrink tumors in the setting of canine brain cancer. The team believes that this combined therapy will improve the response in dogs that already have spread of OS to the lungs and will also improve their survival. 

POTENTIAL IMPACT: If the study results are positive, the treatment approach of combining oral medications with a tumor vaccine could become widely available to dogs with OS. Lastly, because the vaccine can be made to be specific for different kinds of cancer using cancer cell lines rather than tissues from a biopsy, this approach has the potential to treat dogs beyond those with OS.