Osteosarcoma (OSA) is the most common type of bone cancer in dogs.
It is an aggressive cancer that causes pain in the affected bone and lameness, and weakens the bone structure making it likely to fracture spontaneously. The tumor frequently spreads to the lungs and also to other bones.
Standard treatment consists of amputation of the affected leg, followed by chemotherapy to prevent or delay the spread of the tumor (metastasis).
Even with this treatment, the majority of dogs still develop metastasis and die from OSA within one year of diagnosis.
When amputation is not an option (for either medical or personal reasons), treatment is directed at decreasing the pain caused by OSA.
Palliative radiation in combination with pain medications provides pain relief in up to 85 percent of dogs. However, these treatments do not usually prevent disease progression and most dogs will succumb to intractable pain or pathological bone fracture within three to five months of diagnosis.
Immune Therapy for the Treatment of Osteosarcoma
The immune system plays an important role in identifying and killing cancer cells in the body.
The Mason lab is currently evaluating a vaccine, called ADXS31-164, that aims to stimulate the body’s immune system to recognize and kill bone cancer cells.
The vaccine is made from the bacteria Listeria monocytogenes, which has been genetically modified to express a tumor protein (HER-2/neu) that is found in many cancer cells, including canine osteosarcoma.
The bacteria is highly attenuated, which means it has been weakened so as not to cause disease when administered to the patient.
The vaccine is given by intravenous injection and aims to stimulate an immune response against cells that express the tumor protein (HER2/neu).
In this way, it is hoped that the immune system can be trained to recognize both primary and metastatic cancer cells and eliminate them, helping to delay the onset of metastatic disease and in cases where dogs are treated without amputation, prevent primary tumor progression.