Hairy cell leukemia (HCL) is a rare cancer of the bone marrow that causes a growth of abnormal B cells. B cells are a type of white blood cell (or lymphocyte) that fight infections. About 1,000 people are diagnosed with hairy cell leukemia each year. Treatment for HCL is often effective at controlling the disease, and people with HCL generally have a good outlook.
Your doctor may recommend testing if they think you may have leukemia. Diagnostic tests can help your doctor diagnose leukemia, determine which type of leukemia you have, and provide information about treatments that may be helpful.
A physical exam allows your doctor to check your overall health. Your doctor will probably ask you about any current symptoms and about past health problems you’ve experienced. They will likely also check for disease signs, such as swollen lumps and lymph nodes.
During the physical exam, your doctor may also check your spleen. The spleen is an organ found in the upper left side of the abdomen. It destroys old blood cells, and it helps the body fight infections. People with hairy cell leukemia often have an enlarged spleen, called splenomegaly. Your doctor can tell if your spleen is enlarged by feeling the shape of your abdomen.
If your doctor thinks there is a chance that you have blood cancer, they may recommend that you get a complete blood count (CBC). During a CBC, a health care professional draws a sample of your blood. The sample is sent to the lab to measure the levels of each type of blood cell. If you have hairy cell leukemia, you may have low levels of red blood cells (anemia), platelets (thrombocytopenia), and white blood cells. A CBC may show altered blood cell levels before symptoms begin.
A peripheral blood smear can also help diagnose hairy cell leukemia. During this test, specialists view your blood cells under a microscope. If you have hairy cell leukemia cells, the cells will be visible. HCL cells are pale and have long projections on their surface that look like hairs.
Your doctor may also use your blood samples for immunophenotyping. Immunophenotyping tests measure the proteins found on the surface of your blood cells. HCL cells contain specific proteins called CD11c, CD19, CD20, CD25, CD103, and CD123. If immunophenotyping tests show that these proteins are present, your doctor will probably diagnose you with hairy cell leukemia.
Cytogenetic tests also help your doctor learn more about your blood cells. Cytogenetic tests can identify gene changes that tend to be found in cancer cells. For example, most people with hairy cell leukemia have a mutation in a gene called BRAF, which encodes a protein called B-Raf. Finding this gene mutation can help your doctor diagnose you with HCL.
During a bone marrow biopsy and aspiration, a doctor removes a sample of blood, bone marrow, and bone from the hip bone or breastbone. The samples may be examined under a microscope or used for laboratory tests, such as immunophenotyping.
Tests such as an ultrasound or CT scan can show how far your leukemia has spread. It can show whether your spleen, liver, or lymph nodes have grown bigger. Some people with advanced hairy cell leukemia have enlarged lymph nodes because leukemia cells can collect there.
There is no cure for HCL. However, treatments are available that can reduce symptoms and keep the condition under control long-term. The majority of people with HCL are able to use treatments to keep their condition under control for many years.
The goal of treatment is complete remission. If you are in remission, it means that all signs of disease have disappeared: Tests won’t find any HCL cells in your blood or bone marrow, the levels of different types of blood cells in your blood will be normal, and your spleen, liver, and lymph nodes will be normal sizes.
When deciding on a leukemia treatment plan, ask your doctor what results you can expect from each possible type of treatment. Additionally, ask about what side effects you are likely to experience, considering your age and other health factors.
Most people with hairy cell leukemia begin treatment right away. However, because HCL is so slow-growing, some people may be able to wait to start taking medication if they aren’t experiencing any symptoms. If you are following a watch-and-wait approach, you will not receive any treatments. You will need to have regular follow-up appointments with your doctor to keep an eye on how your HCL is progressing.
The advantage of watch and wait is that you can avoid treatment side effects for some time. Many drugs or treatments used to manage cancer can cause side effects that may make you feel sicker or decrease your quality of life. By waiting until you have more clear signs of disease, you can feel better for longer periods.
HCL has long been treated with a type of chemotherapy drug called a purine analog. Purine analogs include Nipent (pentostatin) and Leustatin (cladribine ). Pentostatin is an IV infusion that you take every two weeks for three to six months. Cladribine is given either as a continuous IV infusion or as a daily injection over the course of several days. These medications lead to complete remission for most people with HCL.
Targeted therapy drugs attack specific molecules located in or on cancer cells. Lumoxiti (moxetumomab pasudotox) is a targeted therapy drug approved by the U.S. Food and Drug Administration to treat HCL. People who have previously tried at least two other treatments, including either pentostatin or cladribine, can typically try moxetumomab. Moxetumomab blocks a protein called CD22 that is found on the surface of HCL cells.
HCL may also be treated with Rituxan (rituximab). Rituximab is a monoclonal antibody — a man-made antibody that attaches to and blocks the protein CD20. Combining rituximab with cladribine often leads to better outcomes than the use of cladribine by itself.
Immunotherapy treatments help boost the body’s immune system to kill cancer cells. Intron A (interferon alfa) is an immunotherapy treatment commonly used to treat HCL. Interferon alfa blocks HCL cells from dividing and forming new cancer cells. Interferon is usually given to people who can’t undergo chemotherapy because of other health issues or to those for whom chemotherapy has failed.
Some people with HCL may have a splenectomy (surgery to remove the spleen). Removing the spleen won’t directly treat HCL, but it can relieve symptoms such as abdominal pain. It may also help your blood cell counts return to normal. People with HCL generally only get a splenectomy if the spleen ruptures or if standard chemotherapy drugs don’t work to control the condition.
Researchers are studying new treatments for hairy cell leukemia in cancer research studies and clinical trials. New research can uncover new therapies that may work even better than standard therapies. Clinical trials help doctors determine if these potential new treatments work and whether they are safe.
Current HCL treatments being studied include:
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