Canine Lymphoma (also known as Lymphosarcoma)



Canine Lymphoma (also known as Lymphosarcoma)

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Lymphoma is a highly malignant tumor of the lymph system. It is the most common form of cancer in both humans and small animals. What this means is there has been lots of research and new developments in the treatment of this disease.

What is the Lymph System?

The lymph system is represented by a network of lymphatic vessels and lymph nodes through which foreign proteins and disease organisms are circulated. Lymph nodes serve as processing centers where these types of foreign substances are presented to the immune system. “Lymphocytes” are the main cells of the lymph system. These lymphocytes are circulated through the lymph vessels while also directing foreign substances towards the lymph nodes. These lymph vessels also interface with the blood stream allowing lymphocytes a greater area to patrol.

What is Lymphoma?

When lymphocytes become cancerous within a lymph node, the node swells and hardens. These malignant lymphocytes have no trouble traveling through the highway system of the lymph vessels and affecting all the lymph nodes. Soon all the lymph nodes become enlarged. Ultimately the bone marrow becomes affected, the immune system is destroyed, severe anemia and weakness often occurs. Without treatment, animals with Lymphoma are expected to live for 4-8 weeks from the time of diagnosis. Luckily there are treatment options for dogs with this type of cancer.

Most patients do not feel ill at the time of diagnosis and many people want to wait until they begin to feel sick to begin treatment. This is not recommended the sooner treatment is begun the more effective it seems to be in terms of remission. Dogs also tend to handle treatment better when treatment is begun while they still feel healthy.

How did my dog get Lymphoma?

We do not know what causes cancer in dogs (or people) in most instances. Cancer seems to be caused by a variety of factors such as environment, heredity, as well as lifestyle. A cancer is basically one or a small group of cells in the body that “go wrong”. It appears as though these cells appear often but our bodies generally have ways of destroying these wayward cells before they get out of hand. Sometimes, these cancer cells escape our natural mechanisms and cancer develops. At this time there is no way to know what factors led the development of lymphoma.

What happens now?

Once the diagnosis of lymphoma has been made basic blood work and urinalysis is usually recommended to assess the patient’s overall health and ability to handle the medications used to treat this disease. Treatment typically consists of a combination of chemotherapy medications and steroids given over a 25 week period. During these treatments a complete blood count is performed on a weekly basis to evaluate the patient’s red and white blood cells count. This helps us to know how well the patient is handling the medications and also when the medications are given.

Treatment of lymphoma in our pets is approached differently than in humans. In our pets the goal of treatment is prolonged remission. Remission is the state in which tumor symptoms have been abated and the patient is comfortable. During remission the patient is indistinguishable from any other dog without cancer. During remission the tumor is reduced to undetectable levels and lymph nodes are returned to normal size. Length of time in remission is dependent on many factors such as the chemotherapy protocol. The protocol mentioned above have an average remission of 13 months with approximately 25% of patients surviving for more than 2 years after treatment.

In humans the goal of cancer treatment is complete cure. Although it is theoretically possible to achieve a cure in our pets it is not practical. For this reason treatment focuses on giving the patient the longest possible survival time along with a good quality of life. For these reasons our goal is prolonged remission.

Frequently asked questions about chemotherapy

Should we see an oncologist?

It is never a bad idea to see a specialist. Treatment for lymphoma is constantly evolving and a specialist may have information your general practice veterinarian may not have access too. However, lymphoma is very common in dogs and is often treated by the patient’s regular veterinarian. This veterinarian will research which protocols are proven most affective as well as which work best for your pet’s situation.

Will chemotherapy make my dog sick?

In most cases the answer is no. While nausea or infection is possibilities, most dogs do not experience any of these complications. Only about 7% of dogs treated with chemotherapy require hospitalization due to chemotherapy side effects.

Will my dog lose hair or go bald?

While some patients lose whiskers, substantial hair loss is not experienced by dogs on chemotherapy. The only exceptions to this are breeds such as Old English Sheep Dogs, Poodles, Lhasa apso, and Shih Tzus. This is due to the way hair growth occurs in these breeds as opposed to most dogs.

How will I know when we have achieved remission?

When remission is achieved lymph nodes will have returned to normal size and any other signs of illness related to the cancer will have resolved.

How will I know when remission is lost?

The most obvious sign will be that lymph nose enlargement has returned. This means that a new round of medications must be started (this is called a “rescue”).

How long will my dog have a good quality of life on chemotherapy?

This depends on the protocol chosen as well as how well any particular individual will do relative to the “average” response. For more information on different protocols please speak with your pets veterinarian about the particular protocols advised for your pet.

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