Guide to Canine Cancer

Overview

Hearing that your dog has canine cancer does not mean the end of its life. Like cancer treatment in people, there are now many options for treating your pet. In general, treatments tend to be more effective and have fewer side effects. Cancer is seen in about 1,100 of every 100,000 dogs and is treated by a veterinary oncologist.

Cancer is often referred to as a tumor, which is any sort of lump of bump. Tumors that grow are called neoplasms. There are two types of tumors:

• Benign: Tumors that grow slowly and don’t spread to other parts of the body are considered benign as they have not metastasized or spread. A benign tumor is treated with surgery.
  
  
• Malignant: These tumors are the same as cancer and are also called carcinomas, sarcomas and lymphomas depending on where the cancer is on the body. As the cancer spreads from one part of the body to another, it can enter the lymph nodes or circulatory system. The spread is called metastasizing.

Tips For Catching Cancer Early

Here are 5 tips for catching cancer in dogs early:

1. Every week feel over your dogs skin for bumps and lumps. 
2. Inspect the mouth for anything unusual or that has changed.
3. Check skin for changes such as:
   - color
   - swelling
   - blood
   - lumps
   - anything that appears suspicious
4. Track anything that you find in writing. Note the size, date and time. Take a picture if you can.
5. Watch your dogs for signs such as:
   - behavioral change
   - appetite loss
   - changes in activity or interest in activities
   

Types of Canine Cancer and Tumors

• Dog Neoplasia Overview
• Anal Gland Tumors
• Bladder Cancer
• Breast Cancer
• Bone Cancer
• Benign Bone Tumors
• Chondrosarcoma
• Hemangiosarcoma
• Intestinal Cancer
• Kidney Cancer
• Leukemia
• Alternative Treatment Options - Leukemia and Other Cancers
• Liver Tumors
• Lumps and Bumps on Skin
• Lymphoma
• Lymphosarcoma
• Mammary Cancer
• Multiple Myeloma
• Osteosarcoma
• Prostate Cancer
• Prostate Cancer in Dogs
• Skin Cancer
• Spleen Cancer
• Stomach Cancer
• Thyroid Cancer

What is Canine Cancer?

In a normal dog cells are constantly dying and being replaced. In a dog with cancer, something is wrong with the replacement cells (called mutant cells). These mutant cells reproduce quickly and form into large groupings. Since these cells are mutant, they cannot provide the same function as the healthy cells they replaced. If these cells or cancer grows, it eventually replaces healthy tissue and causes the dog to die.

High Risk Breeds and Types of Cancer

• Airdale Terrier* - Lymphoma risk
• Basset Hound – Trichoepithelioma and Lymphoma
  
• Bernese Mountain Dog* - greatest incidence of cancer in a 20-year study of nearly 75,000 dogs
• Boxer and Pug – Mast Cell Tumor
• Bouvier des Flandres*
  
• Boxer*- Lymphoma risk
  
• Bulldogs - Lymphoma risk
• Bullmastiff* - lymphoma risk
• Cocker Spaniel – Ceruminous Adenoma and  Cutaneous Plasmacytoma
• English Cocker Spaniel – Anal sac gland carcinoma
  
• German Shepherd - high risk for hemangiosarcoma
• Giant Schnauzer and Gordon Settler – Subungual squamous cell carcinoma
• Golden Retriever* - high risk for hemangiosarcoma and lymphoma

• Kerry Blue Terrier – Pilomaticoma
• Vizsla and Miniature Schnauzer – melanocytoma
  
• Saint Bernards - lymphoma risk
• Scottish Terrier* – Subungual malignant melanoma and Lymphoma
• Shetland Sheepdog – liposarcoma
• Irish Setter*
• Gordon Setter*

*According to a study in the Journal of Veterinary Internal Medicine that reviewed causes of death for nearly 75,000 dogs from 1984 to 2004, breeds where cancer is more common.

Symptoms

There are several early warning signs of dog cancer symptoms:

• Unusual swelling that continues to grow
• Sores that do not heal
• Weight Loss
• Loss of appetite
• Offensive odor, especially from the mouth
  
• Bleeding or discharge from any body opening
• Reluctance to move or exercise, loss of stamina
• Difficulty eating or swallowing
  
• Loss of energy
• Difficulty breathing, urinating or making a bowel movement
• Sleeping more than usual
• Persistent lameness or stiffness

Symptoms Requiring Emergency Treatment

• Your dog has collapsed
  
  
• Bleeding after receiving chemotherapy
  
  
• Loss of appetite while undergoing treatment

Symptoms Requiring a Call or Visit to Your Veterinarian

• Skin – Sores, bumps, lumps
  
• Leg – Large breed with swelling or a limp
  
• Seizure - In older dog that has a seizure (uncontrolled shaking) for the first time
  
• Nose – blood coming from the nose
  
• Mouth – Lump, bump or growth
  
• Breast – lump or swelling

For more information visit our guide to cancer symptoms.

Diagnosis

Determining if your dog has cancer usually requires more than blood tests or x-rays. Your Veterinarian will need to take a sample of the area in question (a biopsy) and send it to a laboratory to test for the presence of cancer. Cancer cannot be diagnosed visually since an examination of individual cells is necessary. If cancer cells are found (called malignant), your entire dog will need to be examined since many types of cancer can spread.

Testing will help the veterinarian classify the stage of development the tumor is in.  Each stage is associated with a specific treatment protocol or plan and indicates a dog's prognosis (course and outcome of the disease).

Tests for Canine Cancer

Even with the advanced canine cancer tests listed below, it is still possible to miss a small tumor.

• Biopsy – The removal of a small sample (non-excisional) or an attempt to completely remove a cancerous mass (excisional). The biopsy is sent to a lab for analysis. A veterinarian may remove an entire lymph node to see if cancer has spread or if cancer of the lymph nodes exists.
  
  
• Fine-needle Aspiration (FNA) – Like a biopsy, but instead of surgery, a needle is used to extract cancerous cells for testing.
  
  
• Blood Tests (CBC) – Changes in the composition of blood could indicate problems such as low red blood cells, high white blood cells or changes in kidney and liver function.  These test are called a chemistry profile and blood count. There are recent advances in cancer treatment and diagnostics based on genetics. One approach is called "liquid biopsy." In this approach the blood is analyzed for DNA mutations that are associated with cancers. The test shows if cancer is present, if your dog has gone into remission or if a relapse has occurred. The FDA has approved liquid biopsies for human cancers, but some of the same human DNA mutations are found in canine cancer. 
• X-Ray – An x-ray will detect tumors in the lungs, chest or bones.
  
  
• Ultrasound – The best technique for detecting tumors in the abdomen. A biopsy would be needed to confirm any findings.
  
  
• Endoscopy – A video camera on a thin tube that is inserted into the mouth or nose to look for tumors. Used to examine the colon, bronchi and stomach. 
  
  
• Surgery – To examine any area in question.
  
  
• CT/MRI Scans – Best technique for detecting tumors that are near bone are unable to be seen by X-rays. 
  
  
• Urinalysis- To check urine components
  
  
• Bone Marrow Aspirate - The removal and testing of bone marrow
  
  
• Lymph Node Aspirate - The removal of lymph node fluid
  
  
• Immunologic Studies - Testing immune response
  
  

Tumor Node Metastasis Rating System

A veterinary oncologist will use a ratings system that defines the size and spread of a tumor.

Tumor Size or Extent (T=Tumor):

• Tis: preinvasive tumor (in situ)
• T0: no evidence of tumor
• T1: tumor <5 cm in diameter but confined to primary site
• T2: tumor >5 cm in diameter or ruptured tumor
• T3: infiltrative tumor
        a: no bone invasion
        b: bone invasion

N = nodes:

• N0: no evidence of lymph node enlargement
• N1: movable ipsilateral nodes enlarged
• N2: movable contralateral/bilateral nodes enlarged
• N3: fixed nodes

M = metastasis:

• M0: no metastasis
• M1: metastasis detected

Treatment

If a tumor has spread (metastasized) in most cases a cure is not possible, however with advances in veterinary cancer research veterinarian's have more treatment options than ever before. If a tumor is not treatable,  the treatment focus is on maintaining a dog's quality  of life (this is called palliation). Palliation or palliative care seeks to minimize pain and reduce any functional difficulties such as urination and swallowing.

Tumors that have not spread (referred to as being localized) have the best prospects for being cured. Treatment usually involves some combination or single use of immunotherapy (improving the immune system), surgery, chemotherapy or radiation. Curative approaches are commonly used if the tumor can be controlled for one year or longer after the start of treatment.

For example, radiation can be used to shrink a tumor followed by surgical removal of any remaining cells.

Treatment Approaches for Canine Cancer:

Surgery

Cancers commonly treated with surgery include:

• Mammary tumors (except inflammatory mammary cancer) - most prevalent tumor in female dogs.
  
• Prostate tumors
• Oropharyngeal tumors
• Skin cancers
• GI tumors
• Lung tumors
• Bone tumors

Surgery can have complications with risk increasing based on the age of the dog. Complications include incomplete healing, blood loss, wound infection and the formation of abscesses. There is also a risk of death caused by the surgery itself.

Radiation

Radiation therapy is used for many types of tumors. Cancers treated with radiation include:

• Brain tumors
• Small pituitary tumors (can be curative)
• To extend the survival time for spinal lymphomas and intracranial tumors
• Nasal cavity tumors
• Mast cell tumors
• Soft tissue sarcomas
• Thyroid tumors

Downsides include the possibility that the radiation will not reach cells in the center of the tumor. The radiation may effect surrounding skin or the lining of the gastrointestinal tract. Can also cause blindness or organ malfunction.

Chemotherapy

Chemotherapy is used to treat systemic cancers as the sole agent (see list that follows). It is also given to patients that have successfully completed surgery and/or radiation as an additional therapy.  Chemotherapy can improve the effectiveness of radiation therapy while helping to slow down tumor growth.

When used in combination with surgery, chemotherapy can reduce tumor size before surgery. Other benefits include the ability to kill microscopic cells and to slow down tumor growth.

Canine cancers treated with chemotherapy include:

• hematologic malignancies
  
• metastatic carcinomas
• Metastatic sarcomas
  

Problems with chemotherapy include toxicity, problems with the immune system and anemia. Symptoms can include vomiting, nausea, problems with wound healing and dog hair loss.

Hyperthermia

Hyperthermia is considered to be the most effective treatment approach when used in combination with chemotherapy or radiation. It is used to treat tumors that are small (<1.0 cm) or malignant and superficial.

The limitations of hyperthermia canine cancer therapy includes that it can damage both normal and cancerous cells. It can also cause skin burns. Like other treatment methods, hyperthermia can be used in combination with radiation and chemotherapy.

With radiation, hyperthermia can double the response to therapy. It can improve survival teams by improving the rate of response to therapy. With chemotherapy the hyperthermia improves that performance of medications that work better at higher body temperatures. It may also protect normal cells against the toxicity of the chemotherapy agents. That said, other studies indicate that the combination of hyperthermia and chemotherapy might increase treatment toxicity.

Photodynamic Therapy (PDT)

Photodynamic therapy for canine cancer is used in a limited number of instances. It is primarily used in dogs that have local (limited to one area) and superficial tumors that are minimally invasive. This includes tumors that are on the lining of the urinary bladder, oral cavity and skin.

Limitations of this type of therapy includes the inability of light to deeply penetrate into the skin or tumor tissue. The dog patient must be kept in reduced lighting conditions for 4 to 6 weeks after treatment. Not all tumors react the same way to treatment.

Gene Therapy

There are four types of gene therapy available to treat dogs:

• Drug resistance gene therapy
• Tumor suppressor gene therapy
• Genetic immunotherapy
• Suicide gene therapy

Anti-Angiogenic Drugs

These medications work by cutting off the blood supply that "feeds" a tumor. These medications are in the early development stages.

Immunotherapy

Immunotherapy uses immune system processes to attack cancer cells. Types of cancer treated include:

• Soft tissue sarcomas (includes hemangiosarcoma and fibrosarcoma)
• Osteosarcoma
• Mastocytoma
• Melanoma
• Lymphoma

There are several types of medications that alter the immune response.  This includes:

• Growth factors
• Antibody therapy
• Adoptive cellular therapy
• Monokines/Lymphokines
• Nonspecific immmunomodulators

Small Molecule Inhibitors

Small molecule inhibitors are used to treat various types of cancer as a standalone treatment or in combination with radiation or chemotherapy. These medications target specific cell functions that are associated with cancer mutation. One example is the drug toceranib phosphate (Palladia), which is approved for the treatment of mas cell tumors in dogs. Another is Laverdia Ca (Verdinexor) which if for treating dog lymphoma. Both of these drugs are oral treatments which are provided at home. 

Alternative Therapies

There are several alternative therapies that can help to reduce pain and other symptoms such as nausea and vomiting.  These include:

Acupuncture:

•  for pain relief any vomiting and nausea that are side effects of chemotherapy and other treatment protocols

Massage:

• In cases where the massage will not interfere with treatment

Herbal Remedies:

• An oncologist might recommend products like C-Caps to strengthen the patient or to address any side effects. If a dog is undergoing chemotherapy or radiation, check with your veterinarian to ensure that products like these can be used.
  

If a therapy is not available, then some dogs can be enrolled in a testing trial at a veterinary college.  A list of universities that are conducting canine cancer trials can be found at the Veterinary Cancer Society.

Nutrition and Diet

In cancer patients, nutrition plays a dual role. It is most important to keep a patient healthy and nourished (to avoid a condition called cancer cachexia, which refers to severe malnutrition in cancer patients). Secondly, it is believed by some that some nutrients can help to slow down or prevent cancer.  Other nutrients may be able to reduce the side effects of radiation and chemotherapy.

In general, a dog cancer diet includes an increase of protein and a decrease in carbohydrates (carbs or glucose might fuel cancer cells). Other nutrients such as some vegetables, fruits and supplements can have a positive effect.

The problem for dogs is when the cancer alters the metabolism. This tends to happen during the early stages of cancer and will decrease the dog's quality of life over the course of the disease.

See our guide to formulating canine cancer diets for details on all aspects of nutrition and canine cancer diets.

Dog Cancer Treatment Podcast

Here is a helpful podcast on cancer treatment in pets from the American Veterinary Medical Association. The podcast features Dr. Erika Krick, assistant professor of oncology at the University of Pennsylvania School of Veterinary Medicine. The discussion reviews recent development in canine cancer treatment.

             AVMA Podcast

Hemangiosarcoma

Hemangiosarcoma accounts for 30% of all canine cancer cases. Approximately 1/5 of German Shepherds and Golden Retrievers will develop this disease in their lifetime. The disease can be foudn anywhere in the dog's body where there are blood vessels. Areas at risk are the spleen and atrium of the heart. The spleen and heart atrium can rupture, spreading cancerous cells and possibly causing death from internal hemorrhage.

The first sign of hemangiosarcoma in dogs is often a sudden death. The disease causes the tumor to rupture, resulting in bleeding which leads to death. Other signs include tired behavior (lethargy), difficulty breathing, pale gums, heavy panting with no apparent cause, and a distended abdomen.  A dog might appear to recover from a small blood clot, but then ultimately succumb to the disease.

Post diagnosis the survival time is 1 to 3 months., with all dogs diagnosed passing away within a year. Treatments such as chemotherapy and surgery could extend the lifespan by about 6 months. 

Treatment involves spleen removal via a surgery. This is followed by chemotherapy. Researchers are experimenting with treatment depending on tumor location. Given the prevalence in Golden Retrievers, there are many studies underway including at the Morris Animal Foundation Golden Retriever Lifetime Study.  To participate in a clinical trial speak to your veterinarian or contact a  University veterinary research center near you.

Lymphoma

The drug Tanovea (rabacfosadine injection) has now received FDA approval to treat dog lymphoma. This treatment approach is not used for Highland West Terriers since the breed is prone to a condition called Pulmonary fibrosis, which is a possible side effect of treatment. 

Should You Treat a Dog with Cancer

Cancer therapy can require a big commitment from an owner including multiple trips to the veterinarian and related costs.  These are decisions that can only be made by a owner. 

There are five criteria that are used to measure quality of life and canine cancer care. Dogs that score near normal on each factor tend to have better treatment outcomes.

1. elimination of bodily fluids
2. level of activity and exercise
3. weight and condition of the body
4. appetite
5. alertness and mental status

Other methods for measuring quality of life include the ability of a dog to engage in activities that he or she enjoys. See our discussion on euthanasia if you would like some help and support when exploring this difficult decision.

If you decide to not treat the cancer, the focusing on care using alternatives and conventional approaches (called palliative care) for keeping a dog free of pain may be the best approach.  For example, products natural remedies such as C-Caps contain antioxidants which help to strengthen healthy cells and boost a dogs immune system. Again, these types of approaches are considered to be supportive vs. a specific cure.

Lymphoma Treatment

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Brochures on Canine Cancer:

References

Washington State University College of Veterinary Medicine

OncoLink