Canine Lymphoma – Cancer in Dogs
Canine lymphoma, similar to non-Hodgkin’s lymphoma in humans, accounts for approximately 7-14% of all canine cancers and is one of the five most common in dogs. There are more than 30 types described and their behavior can vary widely.
What is that?
A lymphoma arises from white blood cells called lymphocytes, which help the immune system fight infections. Therefore, most lymphomas are found in organs that are part of this system.
Although lymphoma can affect almost any of these organs, it is most often seen in the lymph nodes under the jaw, in front of the shoulders, or behind the stifle (knee) before spreading to another organ, such as the spleen, liver or bone marrow. Some lymphomas grow quickly and require aggressive treatment, while others grow very slowly and can be managed as a chronic disease. Like most canine cancers, lymphoma has no known cause.
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The four most common types are multicentric (80 to 85 percent of lymphomas), affecting the lymph nodes; food (7% of lymphomas), affecting the intestines; mediastinal, affecting the thymus and chest nodes; and extranodal, affecting a specific organ, such as the skin, eyes, kidneys, lungs or central nervous system. (If bone marrow is involved, the diagnosis is lymphocytic leukemia.)
Signs and symptoms.
In the early stages of lymphoma, a dog owner may notice a lump under the dog’s jaw or in the neck without the dog showing any signs of illness. Some dogs may show only mild fatigue or reduced appetite, while others will have more serious symptoms, such as weight loss, weakness, gastrointestinal issues, excessive thirst, or difficulty breathing. . Swollen, nontender lymph nodes are a constant sign.
Lymphomas that appear on the skin (cutaneous lymphomas) are sometimes first diagnosed as an infection or allergy; they begin as red, scaly, itchy patches that eventually turn into red, moist, open sores. Gastrointestinal lymphomas accompanied by vomiting; dark, watery diarrhea; and weight loss. Lymphomas that appear in the chest can lead to breathing difficulties in dogs and/or swelling of the face and front legs.
How is it diagnosed?
To diagnose lymphoma, the vet will take a biopsy of the affected tissue and perform a series of tests to determine how far it has grown. Blood and urine are evaluated, the chest and abdomen are X-rayed, and ultrasound of the abdomen and bone marrow aspiration may be recommended. Abnormalities revealed by ultrasound are often removed by fine needle aspiration, a well-tolerated way to obtain a sample of the mass.
How is it treated?
Depending on the type, lymphoma is generally considered treatable and chemotherapy is the preferred method.
According to experts from the Flint Animal Cancer Center at Colorado State University, “Canine lymphoma is initially very sensitive to chemotherapy. Up to 95% of treated dogs will go into remission when the most effective treatment protocols are used. These protocols involve a combination of drugs given over several weeks to months and are based on a similar protocol used for lymphomas occurring in humans.
A recent therapy, Tanovea-CA1, which has received conditional approval from the FDA, shows great promise. It can be used alone or in combination with other drugs and involves five intravenous infusions of the drug twenty-one days apart. The drug is expensive but may result in a lower overall cost, as the duration of treatment tends to be shorter than other options.
Dogs treated for lymphoma generally have a very good quality of life and often remain in remission for a year or more. About 20% of dogs survive more than two years with proper treatment.
Update: The FDA has announced conditional approval of a new oral drug to treat canine lymphoma. Laverdia-CA1 (verdinexor tablets), which can be taken at home, works by preventing the spread of cancer cells. According to the FDA, “The conditional approval allows veterinarians access to needed treatments while the drug company collects additional efficacy data, such as through trials with customer-owned dogs. The company has then up to five years to complete efficacy studies to support full approval.
Are certain breeds predisposed?
Lymphoma can develop in any breed at any age, although Golden Retrievers appear to be most affected, followed by Boxers, Bullmastiffs, Basset Hounds, Saint Bernards, Scottish Terriers, Airedales and Bulldogs.