New Treatment Therapies for Osteosarcoma By Dr. Deborah Shores

Photo by: Martin Cathrae
Osteosarcoma is the most common form of bone tumor in dogs, affecting mainly large breeds such as the Great Dane, Rottweiler, and Irish Wolfhound. If you are interested in more specifics about osteosarcoma, please take a look at our previous article.

For many years, osteosarcoma has been treated by amputating the affected leg or a treatment called sterotactic radiation therapy (SRT). SRT spares the limb from amputation using radiation and avoiding surgery. This form of treatment can work well in many different tumor sites, including the forearm (distal radius), upper arm (proximal humerus), knee (distal femur) and ankle (distal tibia). 

Osteosarcoma patients are often found to have tumor spread (metastasis) to other areas of the body. Because of this, chemotherapy is used to eliminate any cancer cells that may have spread. Unfortunately, even with chemotherapy treatments, many osteosarcoma patients die within one year of diagnosis from metastasis.

However, a recent study performed at the University of Pennsylvania shows that new treatment therapies for osteosarcoma may be on the horizon. To effectively extend the lifespan of osteosarcoma patients, the cancer cells that have spread need to be destroyed. 

In order to reach this goal, researchers are performing studies on immunotherapy. Immunotherapy is when the dog’s immune system specifically targets and kills viruses and bacteria. If the immune system can be trained to recognize cancer cells, it would be possible for the body to naturally destroy and prevent the cancer from spreading. 

Dr. Nicola Mason, a researcher at The University of Pennsylvania, is leading a trial that will evaluate the safety and therapeutic effects of a bacterial vaccine known as ADXS31-164.  This vaccine contains a bacteria called Listeria monocytogenes. It has been genetically-modified to express Her2/neu, which is a marker that osteosarcoma cells express. The goal is to train the immune system to identity and kill cells that express the marker Her2/neu. 

The study includes dogs that have been diagnosed with osteosarcoma and undergone standard treatment (amputation and follow-up chemotherapy). All dogs receive the vaccine, once every three weeks for a total of three vaccines. Thus far, side effects of the vaccine have only included a mild fever which resolved naturally. 

The preliminary results of the trial have been positive. Multiple dogs have been cancer-free for 500-600 days. As more dogs are treated with ADXS31-164, we will learn more about exactly what this treatment can and cannot do in treating osteosarcoma patients, but it looks like there could be some positive changes in the future of osteosarcoma. 

REFERENCES

1.      Mason, N. (2013, December 15). Penn Studies “Cancer Immunotherapy” Vaccination for Osteosarcoma.SCDA Health & Genetics. (http://sdcahealth.wordpress.com/2013/12/15/penn-studies-cancer-immunotherapy-vaccination-for-osteosarcoma/)

ABOUT DR. DEBORAH SHORES

Deborah Shores, DVM is a graduate of Mississippi State University College of Veterinary Medicine. She has many years of experience working in animal hospitals and clinics from Virginia to South Carolina, treating mainly dogs and cats. She has a special interest in nutrition and holistic veterinary medicine and plans to pursue an acupuncture certificate at the Chi Institute in Florida. 

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