Gastrointestinal Cancer In Dogs

Cancers that originate in the gastrointestinal tract are called gastrointestinal cancers. This could be anywhere between the gastrointestinal tract i.e. stomach, esophagus, pancreas, biliary system, small intestine, large intestine, anus, and rectum. Gastrointestinal tumors develop due to the dysregulated replication and abnormal proliferation of cells anywhere along the intestinal tract.

GI tumors may be either malignant (cancerous) or benign (non-cancerous). Malignant tumors Of the GI tract are aggressive, invasive, and prone to metastasize.

The most common gastrointestinal malignancies are adenocarcinoma, lymphoma, and leiomyosarcoma. While adenocarcinomas crop up more often in the pancreas and large intestine, lymphomas tend to occur anywhere along the GI tract and leiomyosarcomas more commonly in the small intestine.

Canine lymphoma (CL) is the most common gastrointestinal malignancy in dogs. They are malignant, diverse, monoclonal, neoplasms of lymphocytes in dogs especially the lymphoid cells of either B or T-cell immunophenotype. Lymphoma represents 5 - 25% of all tumors and 80 - 90% of hematological cancers.

Lymphoma (more properly called lymphosarcoma) is one of the top five causes of cancer-related deaths in dogs. Middle-aged to old dogs are most affected and the estimated incidence rate is 60 - 100 cases per 100,000 dogs.

The second most common gastrointestinal malignancy is ‘pancreatic adenocarcinoma.’ In spite of its low occurrence when compared to other more common malignancies (lung, colorectal, esophagus, prostate, etc), pancreatic cancer is one of the leading causes of death in dogs.

Colon and rectal cancers are usually grouped under ‘colorectal cancer’ as they both have many features in common. Proximal colon cancer and colorectal tumors are the most common tumors of the large intestine.

Symptoms are dependent on the type of GI cancer.

Canine Lymphoma:

• Swollen lymph nodes or lumps, especially in the neck, around the shoulder blade, behind the knees, and back of the jaw.
• Swelling / Edema of the face and extremities.
• Loss of appetite / Weight loss
• Rashes and other skin conditions.
• Lethargy
• Fever
• Polydipsia / Polyuria
• Breathing or digestive issues.

Intestinal Adenocarcinoma:

• Pain in the belly (abdomen).
• Dark-colored stools (due to intestinal bleeding).
• Loss of consciousness (syncope).
• Lack of coordination.
• Low red blood cell counts (anemia).
• Reduced ability or enthusiasm to exercise.
• Weight loss
• Fatigue / Seizures
• Decrease in the reflex of appendages.
• Muscle twitching

• Survival rate and prognosis are dependent on the grade and stage of cancer, and how promptly treatment is given.
• Most GI cancers getting completely cured is relay uncommon, but treatment can make your dog feel better, with the least side effects. This is called disease remission as the cancer burden would be reduced by at least 50% and undetectable to any readily available screening test.
• Surgical options, radiation, chemotherapy, or a combination of these modalities may be tried.
• Chemotherapy protocols vary depending on the type of cancer.
• Chemotherapy for Lymphoma:
  • CHOP Protocol: Four antineoplastic agents are used in this treatment and they are simply called CHOP.
  • Cyclophosphamide
  • Doxorubicin hydrochloride (hydroxydaunorubicin).
  • Oncovin (vincristine).
  • Prednisone
  • Other lymphoma protocols include a protocol consisting of single-agent doxorubicin administered every 3 wk or a non-doxorubicin-based combination protocol (COP).
• For advanced cancers, surgery is the only option followed by chemotherapy.
• Radiotherapy may be used to shrink cancerous cells prior to surgery or used post-op to reduce the duration of the resulting remission.
• Newer treatment protocols such as immunotherapy, Targeted drug therapy, and monoclonal antibodies are also available.

• After cancer surgery, Dog activities should be restricted activity for about 2 weeks to allow recovery and incision healing.
• A restrictive collar usage is recommended for 10 - 14 days. This prevents the natural tendency of dogs to lick and chew at a wound.
• A diet of roughly 50% meat and 40 - 50% whole grains or non-starchy vegetables is optimal.
• A homemade balanced diet is an alternative to commercial diets.
• Fish oils or fish meals, or whole fish are rich in omega-3 fatty acids.

Prevention is not possible for GI cancer as the causes in dogs is varied. Treatment and survival rates vary depending on the grade and stage of cancer.

Good overall health and early detection are the only ways to prevent GI cancer.

Check your dog on a regular basis and consult your veterinarian immediately if you find any odd lumps or lesions.

Belgian Tervuren, Bouvier Des Flandres, Belgian Shepherd, Collie, Standard Poodle, Norwegian Elkhound, Middle Age Dogs, Terrier Dog Breeds, Irish Setter, Airedale Terrier, Beagle, Boxer, Bulldog, Bullmastiff, Basset Hound, Chow Chow, German Shepherd, Golden Retriever, Poodle, Rottweiler, Saint Bernard, Scottish Terrier.

Medium to large breeds is overrepresented. Female dogs are more reported.

1. Causes:

Causes vary based on the cancer type.

For Canine Lymphoma:

• Mutation in the bone marrow.
• Radiation or electromagnetic fields exposure or living near waste incinerators.
• Certain viral infections (Retroviruses).
• Exposure to carcinogens or toxic chemicals (benzene and phenylbutazone).
• Exposure to herbicides, pesticides, and insecticides.

2. Types:

There are many variations and subtypes of GI cancer as the GI tract includes many vital organs.

For instance, types of colon cancer.

Primary Colon Cancer: Cancer that originates in the colorectal region itself is called primary prostate cancer. Most primary colon cancers are destructive and with high metastatic potential. For example, colorectal Adenocarcinomas (95 %).

Secondary Colon Cancer: Cancer that spreads from another organ or metastasized to the colorectal region.

3. Mortality:

The mortality rate of benign types of intestinal cancer is almost zero. Adenocarcinoma type of cancer is highly aggressive and it should be diagnosed early as well as treated promptly. Sadly less than 50% of dogs live more than 10 - 12 months from the time of diagnosis of malignant intestinal tumors.

The mortality rate depends on the type and severity of gastrointestinal cancer.

Adenocarcinoma and lymphoma of the GI tract are highly aggressive and they should be diagnosed early as well as treated promptly. If it is not discovered in the early stages, then the mortality rate will be higher.

5. Prognosis:

Prognosis can differ based on the time of diagnosis and aggressiveness of the GI tumor. Generally, when the cancer is detected early, before any metastasis, radiation and chemotherapy treatment may be effective. When there is the presence of significant metastasis, vets may recommend against conventional treatment and will treat your dog’s clinical signs to make them comfortable.

Contact your vet right away, if you notice any of the following:

• Ascites (fluid build-up in the stomach).
• Narrow or ribbon-like Stools or bloody / black / tarry stools.
• Pain in the belly (abdomen).

• Diet high in protein, fat, and complex carbs.
• Protein: High protein diet comprising 40% of the dog's calories. Fresh, lean protein (Lean ground beef, White-meat skinless chicken, or turkey).
• Fats: Omega-3 and other healthy fats.
• Complex Carbohydrates: Fibers and starches (Whole Grains, Oatmeal, Brown Rice, Potatoes & Sweet Potatoes).
• Overweight dogs - Lower calorie diets, for underweight dogs - Higher calorie diets.
• Vitamin-rich fruits and veggies: Legumes, such as lentils, peas or beans, cauliflower, cabbage, broccoli, tomatoes, and citruses, such as oranges and limes.

The most favorable prognosis can be expected with early detection and appropriate treatment. This emphasizes the significance of a stomach examination as part of a routine physical examination in all dogs.

For benign tumors, recovery is very good. Proper post-operative care should be provided for 3 months to monitor tumor regression. Malignant intestinal tumor recovery is poor. Many dogs can die within a year from diagnosis or are sometimes euthanized.