About Cancer of the Lymph Nodes in Dogs
Lymphoma is one of the most common kinds of cancer in dogs, making up 10 to 20 percent of all cancers diagnosed in canines. Lymphoma is also known as lymphosarcoma or non-Hodgkin's lymphoma. A malignant cancer, it involves the lymphoid system, which includes the lymph nodes. It can occur in nearly any organ in the body. The disease can affect any dog of any age or breed; however, middle-aged to older dogs and those of particular breeds develop lymphoma at higher rates.
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Risk Factors
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Lymphoma occurs most often in dogs who are between 5 and 9 years old. Rottweilers, Scottish Terriers, Golden Retrievers, Basset Hounds and German Shepherds are more likely than other breeds to develop lymphoma.
Causes
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What causes dogs to develop lymphoma is not known. Theories suggest environmental factors---such as pesticides, herbicides and strong magnetic fields---may play a role in increasing risk factors. There is also some evidence to suggest genetic factors may be involved.
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Symptoms
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Swollen glands, or lymph nodes, are often the first indicator that a dog has lymphoma. These swollen glands may be felt under the neck, in front of the shoulders or at other locations on the dog's body. Sometimes lymph nodes that can't be seen or felt from outside the dog's body may be swollen. Depending on the stage of the disease, the size of the tumor and the location of the cancer in the body, additional symptoms may include vomiting, diarrhea, loss of appetite, weight loss, lethargy, difficulty breathing, increased thirst and increased urination.
Diagnosis
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To diagnose lymphoma, your veterinarian may use various types of testing and tools. These may include X-rays, ultrasounds, aspiration of the lymph nodes, thoracic radiographs and bone marrow testing. The doctor will also likely want to do a complete blood count, biochemical profile and urinalysis. These will help with diagnosis and determination of treatment.
Stages
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Lymphoma is classified into five stages with two sub-stages. Stage 1 lymphoma means that only one lymph node or the lymphoid tissue in only one organ is cancerous. Stage 2 means several lymph nodes in one general area are diseased. At Stage 3, all peripheral lymph nodes are involved. Stage 4 includes the involvement of the liver and/or spleen and/or the anterior mediastinum in the chest. At Stage 5, the bone marrow is also cancerous. Sub-stage A means the cancer is not causing symptoms. In Sub-stage B, the cancer is making the dog feel sick.
Chemotherapy
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The treatment pursued for a dog with lymphoma depends on several factors including the stage of the cancer, where the cancer is located in the dog's body and the financial resources of the dog's family.
A multi-drug protocol is often used and includes several types of chemotherapy medications given weekly for 8 weeks, then every 2 weeks for a total of 6 months. A dog with Stage 3A or Stage 4A lymphoma who is treated with this protocol has an average survival time of 1.5 years.
The chemotherapy drug, Doxorubicin, is sometimes used alone for treatment. The dog receives five treatments of the drug at 3-week intervals. Average survival time with this treatment is 10 to 11 months. These two options provide the longest survival times.
Other Treatment Options
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If a dog's guardians choose not to use chemotherapy as a treatment, the steroid prednisone may be prescribed in pill form to be given daily at home. The steroid may help reduce swelling and discomfort, but it is unlikely to help extend the dog's life. Survival time for dogs on this treatment is usually about 60 days.
Surgery is sometimes an option if the dog's cancer is very localized. The surgery is usually followed by radiation treatment.
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References
- Photo Credit Bethney Foster
