Acute leukemia is a systemic cancer characterized by the infiltration of immature lymphocytes or myelocytes (two types of white blood cells) in the bone marrow (and commonly in the liver and spleen as well). Patients with acute leukemia are typically quite ill due to their disease. Affected animals are typically young (less than 5 years of age).  There is a male gender predilection in some studies.

What causes this type of cancer in dogs and cats?

• There are no known causes of acute leukemia in veterinary medicine. In people, certain DNA mutations can lead to acute leukemia, but the causes of these mutations are not known. Most cases of acute lymphocytic and myeloid leukemia are not inherited

What are the common signs of this cancer?

• Patients will have variable degrees of anemia (low red cell count), thrombocytopenia (low platelet count), and neutropenia (low neutrophil (type of white blood cell) count)
• Clinical signs in patients with acute leukemia are usually severe due to the level of bone marrow suppression
• Affected dogs and cats typically have a history of weight loss, excessive drinking and urination, loss of appetite, and lethargy
• Findings on physical examination can include signs of hemorrhage (bleeding), enlargement of the spleen and liver, and lymph node enlargement

How is it diagnosed?

• CBC (with pathology review) / chemistry panel / urinalysis
• 3 view thoracic radiographs (chest x-rays)
• Abdominal ultrasound
• Bone marrow aspirate / evaluation
• Immunophenotyping via flow cytometry—a test that allows veterinarians to evaluate the exact type of white blood cells that are in the blood or bone marrow. This test may be beneficial in distinguishing acute myelogenous leukemia from acute lymphoblastic leukemia from stage V lymphoma, although sometimes telling the difference between these conditions can be very difficult

How is this cancer treated?

• Patients with acute leukemia require aggressive therapy
• Aggressive chemotherapy with a multi-agent IV chemotherapy protocol is the treatment of choice
• The specific chemotherapy protocol will be based on the results of the immunophenotype (which tells us the type of white blood cell)
• Patients may also require intense supportive therapy with treatments such as blood transfusions, broad spectrum antibiotic therapy, IV fluid therapy, and nutritional support
• In-depth monitoring is also required to monitor for signs of infection, signs of bleeding, and signs of abnormal clot formation or DIC (disseminated intravascular coagulation)

What is the prognosis for dogs and cats with this cancer?

• Prognosis of acute leukemia is typically poorer than with lymphoma
• Survival times for those dogs that respond to treatment are around 6 months with some dogs living many more months
• If the patient does not respond to therapy, survival time is usually weeks as infection and bleeding problems are very common with this disease

What is on the horizon for this cancer?

• Bone marrow transplantation is currently the state-of-the-art for the treatment of this disease in people and veterinary oncologists are actively trying to adapt it for dogs