Omya is a fit, active Golden Retriever who loves to swim and play ball! Nine months ago, when she was about 10 years old, my husband and I noticed that she was starting to slow down a little, panted even when she was resting, and didn’t have her old stamina when she was playing. Initially we chalked this up to her getting older, but when she skipped a few meals we knew something really bad was happening. She never misses a chance to eat! We are both veterinarians and knew that in an older Golden, a number of really serious problems could be developing. Sure enough, ultrasound showed she had a very large mass on her spleen and that it was bleeding into her abdomen. Her pulses were weak and her heart rate was pounding, the blood loss was life-threatening.
Emergency surgery to remove her spleen was our best option to stop the bleeding and get her back to her normal activity level as quickly as possible. As veterinarians, we knew that 2/3rds of these masses were highly cancerous (malignant), most commonly hemangiosarcoma. By the time of diagnosis, most hemangiosarcomas have spread to other organs. Her radiographs and the rest of her ultrasound looked normal, so we opted for emergency surgery. Maybe she’d beat the odds and it would be a benign mass. Surgery went well, the spleen was removed and her liver was biopsied to confirm there was no evidence of cancer there. She was pretty much back to her “pre-op” self within days of surgery. Unfortunately, the biopsies of her spleen confirmed she had hemangiosarcoma, though thankfully it wasn’t showing up in the liver yet.
Hemangiosarcoma is a malignant tumor that occurs most commonly in the spleens of large breed dogs, including Golden Retrievers and German Shepherds. Omya presented with the classical clinical signs that occur when the mass ruptures and bleeds. Like Omya, most dogs do not show evidence of metastatic spread at the time of diagnosis, but will develop new tumors – usually in the lungs – within 2 - 3 months of diagnosis. The use of chemotherapy can delay the onset of new tumor growth to 6 - 8 months, but eventually most dogs with hemangiosarcoma do develop new tumors.
We talked with a few local oncologists and learned about a trial at the University of Pennsylvania’s School of Veterinary Medicine, run by Dr. Nicola Mason, who specializes in using the immune system to fight cancers (immunotherapy). She was working on a therapy that would supplemented the standard treatment with a vaccine to help get the dog’s own immune system to reduce one of the factors that promote new blood vessel growth. This type of therapy (gene therapy) is common in treating human cancer and she is trying to bring the technique to treat canine cancers. I very much liked the idea of helping advance canine medicine, and that they were looking at something that was already being used in people. I enrolled her in the trial and committed to heading to the vet school for all her treatments and follow-ups.
The trial aims to determine whether a gene therapy approach could prevent metastatic spread of hemangiosarcoma. The therapeutic being studied is a vaccine that carries a genetic code into the patient’s body. This code instructs muscle and liver cells to make an antibody to neutralizes Vascular Endothelial Growth Factor (VEGF). This growth factor is a critical component to telling the body to make new blood vessels. Dr. Mason and her team hypothesize that this growth factor plays an important role in supporting the growth of the hemangiosarcoma cancer cells that remain in the body after spleen removal and cause the cancer to come back. By using the body’s own immunity to suppress the growth factor, perhaps the tumors couldn’t grow.
The study is a randomized, double blinded, placebo controlled study. But it does mean that Omya may have received a placebo, rather than the study treatment. This is the best design for a clinical trial – enabling the researchers to determine as soon as possible whether the study drug might be having a therapeutic effect. We knew there was a 50% chance Omya would receive the drug and given that all the patients receive standard of care chemotherapy we felt that this was a good gamble to take – she would definitely receive the very best care that veterinary medicine can currently provide AND she might receive an additional drug that could help her.
That decision to enroll Omya on Dr. Mason’s clinical trial was over 9 months ago. Omya received her 5 chemotherapy treatments but we do not know whether she received the study drug or not! What we do know is that currently she has no evidence of metastatic disease and she is back to swimming like a champ in the lake and enjoying this beautiful summer. We don’t know what the future holds for Omya, but we hope that she will continue to do well! We also know that she is very important to the PennVet team’s research because she, together with all the other dogs on this clinical trial, are playing a vital role in showing the doctors whether this new treatment might be able to slow down the progression of this aggressive disease. We are all so incredibly proud of her and the role she is playing. Once the doctors have enrolled all the dogs on the study they will become unblinded and we will find out whether Omya received the study drug! It will be very exciting if she did receive the drug and continues to do well, without evidence of metastatic disease. For now, we enjoy every day with her, and she enjoys every one of the days she has with us! And we certainly hope that more dogs and their caregivers join us in this important study.