Leukemia in Dogs

Leukemia in dogs is rare. Leukemia can be acute or chronic. Acute canine leukemia is more malignant that the chronic form. Read this page to learn more about the symptoms, causes, and treatment of dog leukemia.

Leukemia is a cancer characterized by an abnormal increase in the number of white blood cells in the bloodstream or the bone marrow.

There are different blood cells in the bone marrow, such as lymphocytes, platelets, monocytes, etc. Any one of these blood cells can give rise to cell-specific leukemias. For example, lymphocytic leukemia is a malignant transformation of the lymphocytes (white blood cells). In dogs, lymphocytic leukemia is more common than other forms of leukemia; therefore, this page focuses on lymphocytic leukemia in dogs.

Regardless of the type of blood cell involved, leukemia is a result of genetic mutation in the bone marrow structure, causing it to over-produce a particular white blood cell and under-produce other blood cells that the body needs to survive.

Leukemia is further divided into acute and chronic stages. However, the terms "acute" and "chronic" have a slightly different meaning when it comes to leukemia - They refer to how mature the cancer cells look. Lymphocytes are made in the bone marrow or lymph nodes and they undergo several stages of development before they are released into the bloodstream. An acute leukemia is caused by cancerous lymphocytes that are in their earlier stages of development, whereas a chronic leukemia is caused by lymphocytes that are more developed.

Acute leukemias are generally more malignant than chronic leukemias. In acute leukemia, the cancerous lymphocytes can quickly spread through the blood stream to other sites in the body, most typically the liver and the spleen.

Both stages (acute and chronic) of leukemia in dogs are rare. Acute leukemia usually affects middle-aged dogs or older (6 years or older), while chronic leukemia occurs more frequently in older dogs (10-12 years of age).

Symptoms of Leukemia in Dogs

Acute Leukemia

In cases of acute leukemia in dogs, the bone marrow has suddenly become so busy producing the cancerous lymphocytes that there are deficiencies in other blood cells (e.g. platelets, red blood cells, etc.)

Due to a deficiency of red blood cells, a dog with acute leukemia will show symptoms associated with anemia, such as:

Pale gums
Color of tongue is pale pink to white
Lack of appetite
Weight loss
Weakness
Lethargy

A deficiency of platelets will lead to blood clotting problems. Thus, the dog will have a tendency to bleed or bruise easily.

As well, a deficiency of other healthy white blood cells will lead to poor immunity since white blood cells are the immune system's first line of defense. Therefore, the dog may have recurrent infections and delay in healing time.

Chronic Leukemia

Unlike acute leukemia which can develop very fast, chronic leukemia takes months or even years to develop.

About half of the dogs diagnosed with chronic leukemia show no symptoms at the time of diagnosis. This form of leukemia is usually discovered on a routine blood check. In fact, many dogs with chronic leukemia can survive for up to two years without chemotherapy.

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Causes of Leukemia in Dogs

As in other forms of cancer, the exact cause of canine leukemia is unclear.

It is, however, suspected that certain breeds may be genetically predisposed to the disease.

Also, as in humans, canine leukemia may also result from radiation and certain chemicals and possibly some types of viruses.

Diagnosis of Leukemia in Dogs

Diagnosis of canine leukemia include the use of urinalysis, blood tests (complete blood count), biochemical profile, and bone marrow aspirate.

To determine if the cancer has spread to other sites in the body, the following procedures can be used:

Chest and abdominal X-rays
Abdominal ultrasound
Fine needle aspirate of abdominal organs or lymph nodes

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Treatment of Leukemia in Dogs

The conventional treatment for canine leukemia is chemotherapy. Chemotherapy does not cure leukemia, but may put the disease into remission for several months or longer. Typical chemotherapy drugs used for acute leukemia include prednisone, vincristine, cyclophosphamide, L-asparginase and doxorubicin. Typical drugs used for chronic leukemia include prednisone, chlorambucil, and cyclophosphamide.

Dogs with chronic leukemia have a better prognosis than those with acute leukemia, which, even with aggressive chemotherapy, can achieve remission in only about 30% of the dogs being treated. Without any drug intervention, most dogs with acute leukemia die within a few weeks.