Canine Cancer Treatments

I apologize up front that this blog posting is going to be long. There is so much information on treatments available to diagnosed canines. For dogs with mast cell tumors (MCTs), like Gracie, treatment options may depend on the age of the dog, whether the tumor is benign or malignant, and the stage of the tumor. Canine mast cell tumors account for up to 20% of all skin tumors in dogs. While they often appear small and somewhat insignificant, they can be a very serious form of cancer in the dog.

As I had learned, some MCTs are easily removed without the development of any further problems; others can lead to a life threatening disease. Proper identification and treatment are very important in controlling these tumors. MCTs are deceptive; most often appearing as a button-shaped lesion on the skin. The growth can change in size; growing then shrinking.

Of course I did a considerable amount of research into treatment options to expand on the information my veterinarian shared with me. The treatment of choice for MCTs is surgical. Remove the tumor and biopsy it to determine if benign or malignant. When caught early (stage I or II), surgical removal may be the only needed treatment. It is important that the tumor is carefully removed including a large area of healthy tissue surrounding it. Sometimes it may be difficult to determine exactly where the tumor begins and healthy tissue starts, so a wide margin (large portion of healthy tissues around the tumor) of at least one inch should be removed along with the tumor.

In aggressive cases (like Gracie’s), where there is risk of the cancer returning, or not all of the tumor could be removed, radiation therapy (RT) or chemotherapy may be used to fight the cancer. RT is exposure of the tumor to lethal doses of radiation, minimizing radiation exposure to surrounding healthy tissue in attempt to delay or prevent further cancer growth. RT may also be prescribed if surgical removal may not be an option. Radiation therapy after surgical removal appears to be beneficial. RT may reduce the incidence of reoccurrence and increase survival rates. Radiation is most useful when the tumors have not spread to multiple areas of the body.

If the mast cell tumors have spread to multiple areas, chemotherapy (chemo) is recommended. Chemo would consist of numerous treatments of a combination of anti-cancer drugs including vinblastine, lomustine, and corticosteroids, such as prednisolone. Chemo uses compounds which are toxic to the body and destroys the animal's immune system, hoping that the tumor is killed before the patient. Unfortunately, mast cell tumors do not respond well to these drugs.

While animals do not suffer all of the side-effects as human beings undergoing radiation therapy or chemotherapy, these treatments can still have significant and, in some cases, life-threatening side-effects in dogs. Owners must weigh the benefits and the risks carefully before making the decision to put their pet through radiation treatments or chemotherapy.

Mast cell tumors contain inflammatory substances. The canine’s body releases histamines in response. Histamines are compounds that cause contraction of the smooth muscle and dilation of capillaries. We are most familiar with this with allergies and Benadryl is taken as an antihistamine. High levels of histamines in a dog’s system can cause life-threatening allergic reaction (anaphylactic). Just like with humans, an antihistamine, such as diphenhydramine (Benadryl) is given daily to reduce the histamines in a dog’s system. Dogs with MCTs are prone to ulcers, so an over-the-counter antacid should be given to decrease the amount of acid in the dog’s stomach and prevent ulcers.

On the horizon, there are new drugs being tested in clinical trials. The most promising medication is called Palladia (toceranib phosphate) manufactured by Pfizer Animal Health. In June, 2009, the FDA approved the drug for the treatment of MCT. Palladia is a prescription medication designed to treat grade II-III, recurrent, mast cell tumors of the skin. It is given orally and works in two ways: it attacks and kills the tumor cells and it cuts off the blood supply to the tumor. There are some strict warnings and handling instructions with this medication, so Palladia should only be administered to dogs that are under a veterinarian's care. It is anticipated that this drug will raise the bar on the standard of care. This new weapon is expected to be available in early 2010. This is very exciting news for those canines diagnosed with MCT; unfortunately, is not available now, when my dog needs it.

I also read some articles on alternative methods. One author felt strongly that cancer lies in the immune system, which is why Western treatments may be viewed as not as effective as intended. Stimulation of the patient's immune system to selectively attack the cancer is thought to be the key to achieving a successful outcome. Traditional Eastern medicine has also been used successfully in the treatment of cancer for thousands of years. It is not a replacement for Western diagnosis and therapy, but may be used with Western approaches to help heal patients. When the option for Western therapy is lacking, there are Eastern therapies which can help the patient reduce the rate to cancer expansion or, in some cases, lead to remission of the cancer.

Herbal medications have been shown to lead to spontaneous remissions of cancer. In some cases, these herbal products can be used in conjunction with traditional Western therapies, improving the outcome and reducing the side-effects from Western therapy alone. An integrative approach combining the best of both Western and Eastern medicine seems to be a sensible course of action, providing the best overall care for the patient.

Although eating healthy is the best tool in the fight against cancer, once cancer takes hold certain dietary changes may be help the patient fight against the effects of the cancer. Tumor cells rely heavily upon carbohydrates for their energy and rob the body of amino acids. Tumor cells cannot utilize lipids (fats) for energy, while the rest of the body can. Diets with increased fat content may slow tumor growth, allowing the patient to fight against the tumor. Carbohydrates should be held to a minimum. Recipes are available for owners who prefer to prepare their dogs food. For those who cannot cook for their dog, a commercial food should be of good quality, moderate protein content (18-22%), low carbohydrate content (3-13%), and high fat content (55-60%). One such brand is Mighty Dog Bacon & Cheese dog food. The veterinarian can assist in finding a food which fits these criteria and is appropriate for the patient.

When surgical removal of the cancer is not possible, or when the cancer has already spread to other organs (metastasized), control of the tumor may not be possible by conventional means. The owner must make difficult choices about the continued care of their pet. Some of these choices are very expensive. And therein lays my dilemma. What treatment for Gracie? What can I afford? What will aid in her quality of life?


Citations
Cartoon image. (n.d.) Retrieved November 15, 2009 from http://fuffer.wordpress.com/category/cartoon/

Chan, C. (2009). The C word. Dog World, 94 (10), 36. Retrieved October 30, 2009 from the Ebscohost database.

Clemmons, R.M. (2002). Integrative treatment of cancer in dogs. Retrieved October 30, 2009 from http://neuro.vetmed.ufl.edu/neuro/AltMed/Cancer/Cancer_AltMed.htm

Drs Foster & Smith (n.d.). Canine mast cell tumors: a common cancer in dogs. Retrieved October 30, 2009 from http://www.peteducation.com/article.cfm?c=2+1638&aid=461