What Is Canine Leukemia: How Is It Different From Canine Lymphoma

Though the two cancers interact differently within the cells of the body, their representation through symptoms in the body can overlap.

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What is the difference between lymphoma and leukemia?

As we know, lymphoma is a cancer of the lymphocytes, either B- or T-Cells, in the immune system of the body. The mutation of a lymphoma cancerous cell starts to happen often in the lymph nodes but lymphatics are all over the body so changes can be seen in multiple places. Lymphoma can also extend into the bloodstream when it is more advanced. 

Leukemia is a blood cancer, which means that it can affect any of the 3 types of cells in the blood. White blood cells, red blood cells, or platelets. The alteration of the cells often starts in the bone marrow, where blood cells start to develop from stem cells.¹ The most common leukemia is lymphocytic leukemia which occurs in lymphocytes just like lymphoma does.

Leukemia develops when a cell starts to divide too quickly during the maturation process within the bone marrow. In lymphocytic leukemia, the lymphocyte cells are overproduced in the bone marrow. This can cause crowding out or destruction of other cells forming in the bone marrow such as red blood cells, platelets, and other white blood cells like neutrophils. There are multiple different signs that could develop with lymphocytic leukemia such as low energy, pale gums, bruises, enlarged liver and spleen, and sometimes even enlarged lymph nodes. Some dogs will show no signs and leukemia is found on blood work by elevated lymphocytes.

Like lymphoma, leukemia also has two main categories for diagnosis, ALL: acute lymphoid leukemias, or CLL: Chronic lymphocytic leukemia. Both are treated differently and impact the body in different ways. CLL is the most common manifestation of leukemia in canines.²

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How is leukemia diagnosed?

Leukemia is a blood cancer that can either show nonspecific symptoms such as low energy or symptoms similar to lymphoma. It is diagnosed through regular blood work when the lymphocyte count is elevated or very low. 

Properly identifying the cancerous cells is the most important factor in diagnosing leukemia, due to the interaction with the body being so similar to lymphoma. Like lymphoma, diagnosing leukemia needs to be done with live cells. The tests are similar and look for factors that would determine if a sample is a lymphoma B- or T-cell, or a case of ALL leukemia or CLL leukemia. The difference between those four affected cell types should direct treatment for the patient. 

Tests for leukemia can include bone marrow cytology, molecular diagnosis by polymerase chain reaction (PCR) or immunophenotyping by flow cytometry. These three tests mark cells in a sample in different ways to identify the regularity and repetition of certain mutated cells. Each of these tests can be performed on samples of both blood and bone marrow as well as solid tissue biopsies.³

Bone marrow biopsies are done frequently in people with lymphoma, but not in dogs because it is a more invasive test. In dogs, bone marrow aspirates or biopsies used to be done when a cell line in the blood was either elevated or low and no other explanation such as infection or toxin exposure were found. Unfortunately, it is still very difficult to diagnose acute lymphoblastic leukemia from lymphoma in the blood. 

Now flow cytometry has made it much easier to differentiate between these two. Chronic lymphocytic leukemia can also be diagnosed on flow cytometry. Flow cytometry can be done on a simple blood sample eliminating the need of invasive bone marrow procedures. When the cell lines are low and we do not know why, bone marrow aspirate and biopsy are the central test to diagnose the cause.

Since elevated lymphocytes can be seen with leukemia and advanced lymphoma, it can be challenging to know which one is occurring in the body. Lymphoma most often causes enlarged lymph nodes, but leukemia can also do this. The prognosis between leukemia and lymphoma are very different and why it is important to know which is occurring in the body.

Symptoms of Leukemia in Dogs

• Lethargy
• Lack of appetite
• Fever
• Weight loss
• Nausea
• Vomiting
• Diarrhea
• Increased urination
• Recurrent infections
• Increased intake of water
• Enlarged abdomen, from enlarged liver and/or spleen
• Enlarged lymph nodes

For many patients, symptoms may take a while to be noticed because they will develop gradually or not at all in chronic lymphocytic leukemia. Acute lymphoblastic leukemia can have a rapid onset of illness.⁶ 

Potential causes of canine leukemia

As with any cancer, there is no definitive way to identify the specific reasons that one dog may develop the illness and another doesn’t but there are some aspects of a dog’s life that are often considered risk factors.⁶

• Chemical Exposure: Certain toxins have been associated with leukemia in humans, suggesting a potential risk for dogs as well.
• Genetics: There is DNA in every cell in the body and large segments are called the genome. Changes in the DNA happen all the time, but if these changes are repaired incorrectly or not at all and then lead to the cell staying alive too long and producing more clones, then you develop cancer. Blood cells originate from stem cells with specific instructions for their development and function. When these instructions are faulty, abnormal blood cells may form, leading to leukemia.
• Breed: Chronic lymphocytic leukemia is more frequently observed in breeds like Golden Retrievers and German Shepherds, though the precise genetic mechanisms remain unclear.
• Age: Acute leukemia is more commonly diagnosed in younger dogs compared to middle-aged and older ones.
• Gender: Gender doesn't seem to influence the likelihood of leukemia in dogs; both males and females have an equal risk of developing the disease.

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What is the life expectancy for a dog with Leukemia?

Between the two kinds of leukemia, Chronic lymphocytic leukemia is the best diagnosis to receive. The average age of diagnosis for CLL is 10 to 12 years old, and in up to 50% of cases the diagnosis is often found through regular blood work as the patient doesn’t always show any symptoms of the cancer. 

CLL progresses slowly enough that if a patient doesn’t have multiple conditions, treatment isn’t always necessary to keep the patient around. The average life expectancy after a diagnosis of CLL is one to three years after diagnosis, with a good quality of life. 

When discussing acute lymphocytic leukemia, the outcomes are not always so great. ALL is more aggressive than CLL and requires treatment early after the diagnosis. The average age a dog is diagnosed with ALL is 6 years old, and without treatment, their life expectancy can be as short as a few days. With treatment, many can respond but sadly the response and survival time on average is less than two months.

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How to treat canine leukemia?

Leukemia is almost exclusively treated with chemotherapy. Due to the cancer being in the bloodstream, a treatment that affects the full body is necessary. 

Like with lymphoma, there are various drugs that are used in chemotherapy treatments for leukemia. Because they are adaptive diseases, more options available to treat the development are needed. The ones your pet will receive will be based on the kind of leukemia that they have. For acute lymphoblastic leukemia, the common drugs used in treatment are prednisone, vincristine, cyclophosphamide, L-asparaginase, and doxorubicin. You might notice that several of these drugs are also incredibly effective in treating lymphoma. ALL can also be responsive to a CHOP protocol that is modified for efficacy in leukemia cases.⁵

Some of the drugs commonly used to treat CLL include prednisone, chlorambucil, and cyclophosphamide. There are also cases where a dog with CLL doesn’t need treatment right away because their symptoms are slight enough that they just need regular monitoring. Treatment too soon would be unnecessary. 

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How can ImpriMed help with canine leukemia?

ImpriMed has state-of-the-art labs that are able to help test for leukemia in more detail than some animal hospital labs. To test for leukemia we will run blood tests and perform a flow cytometer test, as well as a PARR test to find the most information about your pet’s leukemia and to verify that the diagnosis is for leukemia rather than for lymphoma. 

After the tests are complete, ImpriMed uses the live cells from the sample to test different chemotherapy drug responses. This test, along with artificial intelligence, is able to identify the best treatment plan available for your pet’s individual, unique cancer cells. 

ImpriMed will provide you and your vet with a Personalized Prediction Profile that will inform you of the best method to treat your pet. It will include responses to individual chemotherapy drugs as well as a CHOP protocol Response Prediction.

This information will be invaluable for making sure that your pet receives the most effective treatment available. 

Find out how to get your vet involved with ImpriMed today.