Dog Health: Lymphoma in Dogs
Cancer of the lymphatic system is a common cancer in dogs. While any dog may develop lymphoma, Golden Retrievers, Boxers, Labrador Retrievers, Rottweilers, St. Bernards, Airedale Terriers, Bulldogs, and Basset Hounds are commonly affected. Lymphoma is considered a cancer of the immune system because the lymphocyte, which is the affected cell, plays an important role in defense of the body against infections. Lymphoma can rapidly ruin the health of the internal organs and without treatment can become life threatening to the pet within four to eight weeks.
Cause of Lymphoma
The cause of lymphoma is unknown, although there is an increased risk in dogs exposed to herbicide 2,4-D.1 Pups as young as 4 months of age are seen with lymphoma, but 80% of cases are seen in 5- to 11-year-old dogs. The relative risk is significantly higher for boxers. Older dogs tend to survive longer than younger dogs.3
Signs of Lymphoma
While lymphoma can involve any organ in the body, most commonly the lymph nodes are affected. Owners may notice a painless enlargement of the pets lymph nodes; fever is typically absent, and most dogs do not feel or seem sick (unless there some other problems, such as elevated blood calcium). These signs are usually observed in dogs with multicentric lymphoma, the most common type of lymphoma in the dog.
Sometimes the affected lymph nodes will enlarge, then regress to normal size, then enlarge again.
With alimentary lymphoma, affected dogs will show weight loss and often have diarrhea.
Diagnosis of Lymphoma
Diagnosis is obtained by aspiration cytology of the affected organ (usually a lymph node ) and biopsy.
Some dogs develop enlargement of other lymphatic organs, such as the thymus gland, spleen, and liver. Occasionally, lymphoma will affect a dog's bone marrow or central nervous system.
Because lymphatic system is located alongside the vascular system (bloodstream), lymphoma is considered a system or whole body disease and may strike in any location, including skin. Surgery plays almost no role in controlling the cancer.
Treatment of Lymphoma
There are many good options for managing lymphoma and inducing remission for as long as possible while also providing for the best quality of life.1 Lymphomas are classically treated with chemotherapy. Since dogs are treated less aggressively, there are usually fewer side effects than in humans. Single chemotherapy drugs such as doxorubicin may add 6 to 12 good month to your dog's life. Combination protocols (mixes of chemotherapy drugs in a carefully planned dosage) can keep dogs cancer free for up to 3 years.
The treatment goal is to get a remission and to then keep it as long as possible. Ideally, the first remission lasts for 6 to 12 months.
Inductions protocols use high levels of very strong drugs to knock the cancer down dramatically right at the start. This minimizes the chances of cells developing drug resistance. A maintenance protocol may use different drugs, lower dosages, or less frequent treatments.2
References:
1. The Natural Vet's Guide to Preventing and Treating Cancer in Dogs. Shawn Messonnier
2. Cancer and your pet: the complete guide to the latest research, treatment. Debra Eldredge, Margaret H. Bonham
3. Tumors in domestic animals. Donald J. Meuten
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