While stomach cancer in people is rather common, stomach cancer in dogs is rather rare. It accounts for about 0.1 percent (1 in 1000) of all canine cancers.
Certain breeds seem to be more predisposed to stomach cancer. For example, Chow Chows have between 10 to 20 times the risk of stomach cancer compared to other breeds.
Other breeds that are more prone to stomach cancer include the Akita, Belgian Sheepdogs, Irish Setters, Keeshonds, Norwegian Elkhound, and Scottish Terriers.
Dog stomach cancer is most frequently caused by adenocarcinoma, a tumor which forms in glandular tissue and spreads to the stomach. This type of tumor can also frequently spread to lymph nodes, the liver and the lungs.
Other less common tumors that cause canine stomach cancer include gastrointestinal stromal tumors, leiomyosarcomas, lymphomas, mast cell tumors, extramedullary plasmacytomas, and fibrosarcomas.
Benign Stomach Tumors
Not all tumors in the stomach are cancerous. There are also benign tumors such as leiomyomas and polyps. These non-cancerous tumors can be removed surgically and the prognosis for dogs with benign tumors is very good.
Stomach cancer in dogs usually occurs in middle-aged to older dogs. It seems to affect male dogs more frequently than females.
Symptoms of Dog Stomach Cancer
The signs of stomach cancer can be very vague and subtle.
The most common symptoms of stomach cancer are vomiting (very often you can see blood in the vomitus) and weight loss.
Dogs with stomach cancer also suffer from abdominal pain, which can cause behavioral changes in the dog.
For example, if you touch the dog, he may growl, whine, or snap at you. He may be reluctant to move and play, and may even refuse to eat.
Other symptoms that could indicate stomach cancer include:
Diagnosis of Dog Stomach Cancer
As you can see, symptoms of stomach cancer in dogs are very vague and many other GI problems cause similar symptoms.
A series of initial tests such as blood, urine and fecal sample tests and x-rays are necessary.
If other GI problems are ruled out, double-contrast radiography and/or abdominal ultrasound can be used to determine if a tumor is present in the stomach.
Endoscopic examination of the stomach is another useful diagnostic procedure. Besides looking for abnormalities in the stomach, the endoscope can remove small samples of the tumor in the stomach for further analysis.
Finally, if cancer is strongly suspected, the vet may suggest exploratory surgical biopsy.
Conventional Treatment of Dog Stomach Cancer
Unless the cancer form is lymphoma, the conventional treatment of choice for stomach cancer in dogs is surgery, provided that the cancer has not spread to other sites of the body.
Sometimes the tumor is so large that food cannot pass from the stomach to the intestine.
In such cases, a bypass surgery may be necessary. Bypass surgery is not curative. It only provides relief to make the dog feel better and to help him stay alive longer.
Radiation therapy is seldom used to treat canine stomach cancer due to the location of the stomach. Radiation may accidentally harm important organs close by (e.g. the liver and intestines).
Chemotherapy is largely ineffective against stomach cancer.
Unfortunately, stomach cancer in dogs is aggressive and prognosis is poor.
Even with surgery, the survival time for most dogs is less than 6 months (median survival time for adenocarcinoma with surgery is 2 months).
Although stomach cancer in dogs is rare, when it occurs, it is usually aggressive. Since the symptoms are similar to those of common digestive issues, diagnosis may be too late and the cancer may have already spread to other parts of the body.
It is therefore important to take your dog to a vet for a checkup if the dog consistently shows signs and symptoms of GI issues, such as vomiting and diarrhea.