Cancer treatments are constantly changing as scientists discover new ways of tackling this disease. Historically, the main options to manage tumors in pets were surgery, radiation therapy and chemotherapy. Surgery and radiation are still used in veterinary oncology, but there have been many new developments in the field of chemical treatment of cancer.
The most common chemotherapy drugs exert their effect by destroying cells that are actively replicating. While they are effective against cancer cells for this reason, they also kill healthy cells, particularly in the intestine, hair follicles, and bone marrow because they are rapidly dividing as well. This accounts for the more common side effects of chemotherapy, such as diarrhea, hair loss and bone marrow suppression.
Research has identified specific factors that cancer cells need to grow, such as the ability to avoid the pet’s immune system and the ability to resist the body’s signals to slow down their rate of replication. New drugs have been developed specifically to target such factors, which means fewer side effects and a better response to treatment.
New Developments in Cancer Treatment for Pets
Different cancers respond to different treatments. Learn about your pet’s new treatment options for fighting this deadly disease.
This drug is licensed to treat a common cancer in dogs known as a mast cell tumor. These tumors often have a defect in a protein that encourages the cancer cells to proliferate and migrate through the body. Palladia attaches to this protein and turns it off. This slows the growth rate of the tumor and helps to prevent it from spreading without any effect on normal cells. Clinical trials are now being conducted into the effectiveness of Palladia against other types of tumors, in particular hemangiosarcoma.
For cancer cells to survive, they have to be able to avoid being destroyed by the body’s immune system. Immunotherapy aims to help the pet’s immune system to identify and destroy cancer cells. Oncept is a drug that treats oral melanoma in dogs. Melanoma cells produce lots of tyrosinase, which is a protein also present in normal canine cells. Oncept contains the gene for human tyrosinase and when it is injected into dogs, it produces the human tyrosinase protein. This is different enough to the dog tyrosinase that it triggers an immune response to it. However, it is still similar enough to canine tyrosinase that when the body attacks tyrosinase, it also attacks the canine protein on melanoma cells and kills them. The result is a longer survival time in dogs with melanomas in the mouth.
Other immune-system-based therapies involve production of antibodies against specific proteins on cancer cells. When the antibodies bind to the cell proteins, the immune system destroys them. Current studies are looking into the development of such antibody-based treatments for canine lymphoma.
Chlorambucil and Cyclophosphamide
These are two drugs that are widely used for chemotherapy in pets currently, but they are starting to be used in a different way. Traditional use involves giving large doses to destroy cancer cells, but this treatment protocol has side effects; because the pet needs time to recover between doses, the cancer can still progress. By giving continuous small doses of these drugs, known as metronomic doses, the blood supply to the tumor is inhibited and the immune response in the area of the cancer is stimulated. Without a good blood supply, a tumor can’t grow. There are also studies being done into antibodies that interfere with proteins involved with blood vessel growth, and these would have a similar effect.
Traditional chemotherapy drugs, in combination with surgery and radiotherapy, are still the mainstay of treating cancers in pets. However, these new developments can result in more effective treatment with fewer adverse effects on the pet. Cancer therapy research is still in its infancy and there’s no doubt that major advances are still to come.