November is designated as National Pet Cancer Awareness Month. One of the common types of cancer in pets is Lymphoma. This designation should help draw attention to the prevalence of this deadly disease and the advances being made in treating it.

What is Canine Lymphoma?

Lymphoma is a type of cancer that is common in dogs and people. It is one of the most common canine cancers, accounting for 7 to 24% of all canine tumours and 85% of all blood-based tumours. In dogs, lymphoma refers to a group of approx. 30 different cancers that originate in the lymphocytes - a type of white blood cell that helps the immune system fight off infection. They are found in organs that support the functioning of the immune system such as the spleen, bone marrow and lymph nodes. Therefore, lymphoma tends to target those areas, although it can affect any organ in the body.

Lymphoma typically progresses very rapidly, and the average survival rate for untreated dogs is only four to six weeks.

What causes Canine Lymphoma?

The cause is unknown but experts believe there are likely many genetic and environmental factors that play a role. Exposure to chemicals or toxic substances like herbicides is one area that is being explored. Exposure to radiation or electromagnetic fields may be another factor.

The disease is more common in dogs that are six years of age or older, but can even strike in younger dogs.

Canine Lymphoma Symptoms

The symptoms vary widely based on the type of lymphoma. With multicentric lymphoma, the first sign of the disease is swelling of the lymph nodes. This swelling tends to be most noticeable to pet owners in the dog’s neck, chest and behind the knees. Often there is no other sign of illness initially. If the cancer is not treated, these dogs will tend to develop fever, lethargy, weakness, dehydration and weight loss as the disease progresses.

Dogs with alimentary lymphoma will typically display vomiting, diarrhea, abdominal pain and weight loss. Dogs with mediastinal lymphoma develop lesions in the chest cavity that cause shortness of breath and coughing. They may also have swelling of the front legs or the face and increased thirst resulting in increased urination. The symptoms of extranodal lymphoma depend on the organ affected but can include blindness, kidney failure, seizures, bone fracture and respiratory distress.

Diagnosing

If canine lymphoma is suspected, your veterinarian will perform a full physical exam as well as lab tests to determine blood cell counts and to look for other biochemical indicators of the disease. Fluid from the lymph node is collected and analyzed to assess the type of lymphoma. X rays and ultrasound exams may also be performed. This will allow your veterinarian to determine if cancer is present and if so, what type and which organs or systems are affected.

Treatment

Although lymphoma is not curable, it is one of the most successfully treated cancers and most dogs will respond to treatment. The traditional treatment has been chemotherapy - generic human drugs that have been around for decades and adapted for use in the veterinary setting. Dogs tend to respond well to chemotherapy and typically tolerate it better than humans do. Treatment plans have the potential to put canine lymphoma into remission giving pets and their owners more quality time together. However, in the majority of cases, the disease will eventually return. With ongoing research, there is hope that one day a cure for lymphoma and ultimately all cancers will be found.