Lymphoma in Dogs and Cats

Monday, September 01, 2008

Michelle Cohen, DVM, Diplomate ACVIM (Oncology), Diplomate ACVR
Garden State Veterinary Specialists

Lymphoma, also known as lymphosarcoma, is one of the most common cancers that we see in dogs and cats. Lymphoma is a cancer of a type of white blood cell called a lymphocyte. Lymphoma is a very treatable type of cancer.

Lymphoma occurs in approximately 1-2 /10,000 dogs and accounts for up to 20% of all cancers in dogs. Lymphoma is most commonly seen in middle aged to older dogs, however can be seen in young dogs as well. The most common form of lymphoma in dogs is called multicentric lymphoma. With this type, the lymph nodes become enlarged. Lymph nodes are located all over the body, but when they become enlarged, can be felt under the jaw, on the shoulders, in the groin region, and behind the legs. Approximately 60% of dogs will not be symptomatic at the time of diagnosis and the only signs are enlarged lymph nodes, detected either on routine examination, or an astute owner. Because it is a cancer of white blood cells, lymphoma can travel through the body and can affect internal organs including liver, spleen, lungs, and bone marrow. Eventually, the dog will show signs from the lymphoma. These signs can include trouble breathing and swallowing because of the size of the lymph nodes, or vomiting, weakness, and inappetance, from internal involvement, and/or systemic effects of the lymphoma.

Lymphoma is a very rapidly progressive disease. Typically without treatment, the average survival is approximately 4-6 weeks. Lymphoma is a very treatable but not often curable type of cancer. With aggressive treatment, the average survival is approximately 1 year with many dogs living 2 or more years. The standard treatment is chemotherapy, which most dogs tolerate well. Fortunately we do not usually see the same side effects in veterinary patients receiving chemotherapy that many human chemotherapy patients may experience. Many of the drugs that we administer are the same drugs that are used in people. Approximately 85% of dogs do not have any side effects at all while on chemotherapy. The small percentages of dogs that do experience side effects are usually managed at home with oral medication.

Approximately 90% of dogs go into remission on a standard chemotherapy protocol. Remission means that the cancer is not clinically detectable and the patient is feeling well, but remains latent in the body. Most dogs eventually come out of remission after some time because the cancer develops resistance to the chemotherapy. If this occurs, we can use other chemotherapy agents and/or radiation therapy. There are a variety of chemotherapy protocols available. The most aggressive protocols usually require an intensive treatment protocol consisting of an induction phase (usually weekly treatments for approximately 2 months) and then a maintenance phase of less frequent treatments. There are other less intensive treatment options available, such as oral or injectable treatments given less frequently. These options are less aggressive and achieve a shorter survival. Steroids can be used in patients as a sole treatment for owners that do not want to pursue treatment and help a patient feel better for a couple of months.

Although cats can get multicentric lymphoma, we more frequently see solitary lymphoma, or lymphoma localized to a single organ or lymphoid tissue. Gastrointestinal lymphoma is one of the most common types of lymphoma seen in cats. Clinical signs often can include 1 or more of the following symptoms: weight loss, vomiting, diarrhea, and inappetance.

There are 2 main types of gastrointestinal lymphoma that can be seen in cats. Lymphoblastic or large cell lymphoma often forms masses in the intestines with or without lymph node enlargement. Surgery, if possible, is recommended to remove the cancer. Because it is a cancer of blood cells, it will likely spread to other organs, therefore aggressive chemotherapy is recommended. Cats, like dogs, also tolerate chemotherapy well. With this type of treatment, the average survival is approximately 6-12 months, depending on the stage of the cancer, however, about 1/3rd of cats with treatment live at least 1.5 years. Without treatment the average survival is approximately 1 month.
The other type of gastrointestinal lymphoma is small cell or lymphocytic lymphoma. This type of lymphoma is more slowly progressive and clinical signs are less pronounced but can include weight loss initially, then vomiting and diarrhea. This type of cancer causes thickening of the intestines but does not cause masses until late in the course of disease. The treatment for small cell gastrointestinal lymphoma is not as intense as large cell lymphoma and usually consists of oral chemotherapy at home. Prognosis is good, with average survivals of approximately 2 or more years.

Garden State Veterinary Specialists’ Oncology Department offers a full spectrum of treatment options and works closely with your primary veterinarian to provide your pet the best veterinary medical care.

This article is for informational purposes only and should not be used as a substitute for the professional advice of your veterinarian.

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