What is a leukemia?

Leukemias are cancers of the blood cells. They generally arise from the bone marrow, and occasionally from the spleen. They are generally associated with a high white blood cell count, although it may occasionally be within normal limits when the cancer cells are “trapped” within the bone marrow. Because they invade the bone marrow, which is where all the blood cells are built, it is often associated with a decreased immune system (higher risk of infections), anaemia and decreased platelet count (higher risk of spontaneous bleeding).

Leukemias are uncommon to rare cancers in dogs and cats, and literature is unfortunately very limited.

What are the different types of leukemias?

There are many different types of leukemias, classified on their cell of origin and aggressiveness. Most white blood cell types include lymphocytes, neutrophils, and monocytes, all part of the immune system. Leukemias of the lymphocytes are called lymphocytic/lymphoblastic leukemias, whereas other leukemias are called myeloid leukemias.

When leukemias are aggressive and progress rapidly, they are qualified as “acute”; and when they are indolent and progress slowly, they are qualified as “chronic”.

How can I tell if my pet has leukemia?

Most pets with leukemias have vague clinical signs including decreased appetite and decreased energy level. They can be presented with a few weeks’ history of waxing and waning symptoms with occasional infections. The gums may also be paler than normal when they are anaemic.

What causes leukemias?

We do not know exactly what causes leukemias, and it is likely that genetic and environmental factors play a role. Some specific mutations similar to what is found in human have been reported in dogs as well. In cats, some viruses such as felv and FIV may be involved.

How are leukemias diagnosed?

Complete blood cell counts are generally the first test that leads to a suspicion of leukemia. A high white blood cell count is noted in most cases, and can be accompanied with a decease in neutrophils (immune cells), anaemia and decreased platelets. A blood smear is then performed to confirm the presence of an abnormal population of cells in the blood. 

Flow cytometry is also recommended. This test is able to identify some specific markers expressed by the cancer cells, which is particularly important to try and confirm the type of leukemia.

A bone marrow aspirate may also be performed to confirmed the presence of the leukemia within the bone marrow. Other tests such as thoracic radiographs, abdominal ultrasound, liver and spleen fine-needle aspirates may also be considered to assess the extent of the cancer. 

White blood cell scattergram of a dog with a B-cell chronic lymphocytic leukemia. Note the very high lymphocyte count (97×109/L) indicated with blue dots.

White blood cell scattergram of a dog with an acute myeloid leukemia. Note the very high cancer cell count (104×109/L) indicated with red dots, wrongfully identified as monocytes by the machine. Note the severe neutropenia (0.5×109/L) as almost no purple dots are present, indicating a higher risk for infection. 

How are leukemias treated?

Since leukemias are diffuse cancers, a systemic treatment such as chemotherapy is indicated. Chronic myeloid and lymphocytic leukemias are generally treated with low-dose oral chemotherapy from home. 

Acute myeloid and lymphoblastic leukemias require standard dosages of chemotherapy, generally administered intravenously although oral drugs exist. In human, bone marrow transplants are often performed, but this form of treatment is nor readily available for our pets. The management of acute leukemias is challenging and demands some commitment from the owner and the medical team.

A very important part of the initial management of acute leukemias is supportive care, necessary because of the bone marrow suppression and clinical deterioration often encountered at the time of diagnosis. Most patients require blood transfusion and occasionally erythropoietin injections to manage the anaemia. Prophylactic antibiotics may also be indicated to reduce the risk of infection when the immune cell count is too low.

What is the prognoses of leukemia?

Leukemias are generally considered incurable cancers in dogs and cats. Long-term survival of several years is commonly seen in chronic leukemias, whereas acute leukemias have a poorer prognosis of only few months.

Our team at AURA is invested to develop new combinations of drugs to try and improve the outcome of acute leukemias. This uncommon cancer may also be challenging to manage initially because of the bone marrow infiltration, and referral to skilled and experienced oncologists should be considered. 

Patient Stories

Leo Monet