Eosinophilic leukemia is a blood cancer that affects eosinophils (a type of white blood cell). Eosinophils are a part of the immune system. They help the body fight infections from bacteria and parasites, kill old or damaged cells, and play a role in allergic reactions. Eosinophilic leukemia can be acute (fast-growing) or chronic (slow-growing). Eosinophilic leukemia is very rare, and experts don’t know exactly how many people are living with this condition.
Chronic eosinophilic leukemia (CEL) is a type of myeloproliferative neoplasm (MPN). MPNs, also sometimes called myeloproliferative disorders, are diseases in which the bone marrow makes too many blood cells. People with CEL have too many eosinophils. CEL can persist for many years, or it can turn into acute myeloid leukemia (AML). CEL can also transform into acute eosinophilic leukemia, a more severe form of eosinophilic leukemia.
CEL is often grouped with another condition, called idiopathic hypereosinophilic syndrome (HES). These two diseases both involve high levels of eosinophils and lead to similar symptoms. However, there are a few differences between CEL and HES. People with CEL have higher levels of blast cells (abnormal, immature cells) in their blood or in their bone marrow. Additionally, CEL is a clonal disease. CEL cells are all copies that came from the same parent cell, so they are all genetic clones. In people with HES, eosinophils came from different parent cells and may not all have the same genes.
Scientists aren’t yet sure what causes CEL. Rarely, exposure to certain harmful substances such as smoking and radiation can cause gene changes that lead to eosinophilic leukemia, although experts have not been able to pinpoint a specific cause in most cases.
People with CEL may have high levels of eosinophils within certain tissues or organs — the location of eosinophils can affect which symptoms a person experiences. For example, a cough may indicate that there are too many eosinophils in the lungs. Additionally, eosinophils in the heart can cause cardiomyopathy, a type of heart disease in which the heart can’t properly pump blood throughout the body.
One of the first signs of eosinophilic leukemia is high numbers of eosinophils. Sometimes, routine blood tests performed during a physical exam uncover high eosinophil counts. Blood cell levels are measured through a test called a complete blood count (CBC). If you have more than 1,500 eosinophils per microliter, your doctor may diagnose you with CEL.
You may also need bone marrow tests to see whether there are blast cells — abnormal, immature cells — in the bone marrow tissue. During a bone marrow biopsy and aspiration, a doctor uses a needle to remove some of the bone marrow tissue and fluid from the hip bone or other large bone. The bone marrow sample is then analyzed to look for abnormal cells. If you have increased numbers of blast cells, you may be diagnosed with CEL. If you have very high levels of blast cells, you may be diagnosed with acute eosinophilic leukemia.
Your doctor may also recommend that you undergo tests to examine whether CEL cells are causing organ damage. Imaging tests such as computed tomography (CT) scans look for changes in your liver, spleen, and lymph nodes. Heart tests like an electrocardiogram (EKG) or echocardiogram (ECHO) look for heart damage, identify changes in your heart rhythm, and measure your heart’s shape and function.
Eosinophils have many different functions within the immune system, so having high levels of these cells can be a sign of other health conditions. If you have eosinophilia (high levels of eosinophils), your doctor may perform tests to rule out other conditions before diagnosing you with eosinophilic leukemia.
Eosinophilia sometimes indicates infection, allergy, or an immune disorder. Your doctor may test for parasites, fungi, or bacteria and ask about any places you may have traveled to recently to evaluate the possibility of infection. Your doctor may also ask you about any new allergens (including medications) you might have been exposed to. Depending on your symptoms, your doctor may recommend different tests to look for immune conditions.
One such test is immunophenotyping, which analyzes the proteins found on the outer surface of your cells.
Cytogenetic tests can also be used to look for gene changes that are known to cause different conditions. For example, MPNs and MDS may be caused by chromosome translocations. Translocations occur when a chromosome (piece of DNA) breaks, and the ends attach to different chromosomes. Translocations can result in fusion genes, in which two different genes are connected. Chromosome translocations and fusion genes found in MPNs and MDS include:
If cytogenetic tests uncover any of these genetic changes, your doctor may diagnose you with a different MPN. If your eosinophils don’t contain these gene changes, your doctor may diagnose you with eosinophilic leukemia.
There is no standard treatment for CEL, and doctors treat it with various methods. When recommending a treatment plan, your health care team may consider factors including how healthy you are, your personal preferences, and potential treatment side effects. Treatments typically don’t cure eosinophilic leukemia, so the goal of treatment is often to manage symptoms.
If you have acute eosinophilic leukemia, you may receive some of the same types of treatments commonly used to treat AML.
Treatments include chemotherapy, targeted therapy, immunotherapy, stem cell transplantation, or palliative care.
Chemotherapy drugs attack cancer cells and lower the numbers of eosinophils within the body. One chemotherapy drug that may help with eosinophilic leukemia is Hydrea (hydroxycarbamide or hydroxyurea).
If hydroxycarbamide doesn’t work, other chemotherapy drugs may be used to treat CEL, including:
Chemotherapy drugs may come in the form of a pill that is swallowed or they may be delivered through an intravenous (IV) tube. Deltasone (prednisone) or other corticosteroids are also often given along with chemotherapy.
Targeted therapies are medications that recognize and attack cells with specific genes or proteins. About 10 percent to 20 percent of people with CEL have a protein called FIP1L1-PDGFRA in their cancer cells. Gleevec (imatinib) is a targeted therapy that blocks FIP1L1-PDGFRA. Imatinib often normalizes eosinophil numbers and leads to a good prognosis.
Immunotherapies are medications that activate the immune system to fight cancer cells. Alferon (interferon alfa) is an immunotherapy drug that can help treat eosinophilic leukemia. Interferon alfa may be used when hydroxycarbamide and steroids don’t work.
People with CEL are sometimes treated with a stem cell transplant. During a stem cell transplant, you first receive high-dose chemotherapy to kill all of your cancer cells. The chemotherapy also typically kills many of your healthy blood cells, so you need a source of new blood cells to take their place. To do this, doctors transplant healthy hematopoietic stem cells, which are cells that can create all of the different cell types found in your blood.
Stem cell transplantation doesn’t always work for CEL. Additionally, people with CEL tend to be older, and a stem cell transplant is risky for older adults.
Palliative care aims to relieve symptoms for people with chronic diseases. Palliative care won’t cure the condition, but it can be used alongside curative treatments to improve a person’s quality of life. Some people with eosinophilic leukemia receive extra treatments that reduce symptoms, such as:
It is difficult to know what your outcome might be if you have eosinophilic leukemia. Many studies look at CEL together with HES and other eosinophil conditions in one big group. In one such study, 80 percent of people with eosinophilic conditions lived for at least five years after being diagnosed. People who had a worse prognosis were more likely to:
If you or a loved one has recently been diagnosed with eosinophilic leukemia, it may help to connect with others who share your journey. More than 7,800 people living with leukemia are offering each other advice, asking questions, and providing support at MyLeukemiaTeam. Join the conversation today by commenting below or by creating a post on MyLeukemiaTeam.