NORD gratefully acknowledges Javier Munoz, MD, FACP, Hematology and Oncology, Banner MD Anderson Cancer Center, Gilbert, Arizona, for assistance in the preparation of this report.
Hairy cell leukemia (HCL) is a rare type of blood cancer characterized by abnormal changes in white blood cells known as B lymphocytes. The bone marrow creates too many of these defective cells, known as "hairy cells" because of the thin hair-like projections found on their surface. Overproduction and accumulation of hairy cells causes a deficiency of normal blood cells (pancytopenia), including an abnormal decrease of certain white blood cells (neutrophils [neutropenia]) and certain red blood cells (platelets [thrombocytopenia]). Affected individuals usually exhibit fatigue, weakness, fever, weight loss, and/or abdominal discomfort due to an abnormally enlarged spleen (splenomegaly). In addition, affected individuals may have a slightly enlarged liver (hepatomegaly) and may be unusually susceptible to bruising and/or severe infection. The exact cause of hairy cell leukemia is not known.
Onset of hairy cell leukemia is usually gradual. Symptoms are nonspecific and may include a general feeling of ill health (malaise), fatigue, weakness, fever, night sweats, and/or weight loss. In addition, affected individuals may experience abdominal pain and a feeling of abdominal fullness due to an abnormally enlarged spleen (splenomegaly).
In some cases, affected individuals may have a slightly enlarged liver (hepatomegaly) and may be unusually susceptible to bruising and/or severe, frequent infections. These infections were often the most serious complication of hairy cell leukemia, but occur rarely with advances in treatment.
The exact cause of hairy cell leukemia is unknown.
The specific symptoms of hairy cell leukemia are due to overproduction of abnormal “hairy” cells, which results in a deficiency of the three main types of blood cells – red and white blood cells and platelets. Red blood cells deliver oxygen to the body, white blood cells help fight infections, and platelets assist in clotting to stop blood loss.
Hairy cell leukemia is a rare disorder that affects males four times more often than females (M4:F1). Hairy cell leukemia affects about 6,000 persons in the United States. Approximately 600-800 new cases are diagnosed each year. Most of the affected individuals are males 50 years of age or older. However, the disorder may occur in individuals between 20 to 80 years of age.
Hairy cell leukemia accounts for one to two percent of all cases of adult leukemia. It was first identified in 1958.
Until recently, treatment of hairy cell leukemia consisted of surgically removing the spleen (splenectomy). In rare cases, in which individuals do not respond to drug treatments, a splenectomy may still be performed. Chemotherapy drugs, specifically purine analogs such as cladribine and pentostatin, are now the initial treatment option for most individuals with hairy cell leukemia. Those who do not have any symptoms may not need treatment right away.
The drug cladribine (Leustatin©) has been approved by the Food and Drug Administration (FDA) for treatment of HCL. This drug interferes with the development of cancer cells and has proven to be an effective drug in the treatment of hairy cell leukemia.
The orphan drug pentostatin (Nipent) has been approved by the FDA for affected individuals who do not respond to initial therapy for hairy cell leukemia. According to studies, the drug produced “durable complete responses” in individuals with hairy cell leukemia. The drug is manufactured by SuperGen, Inc.
In 2018, Lumoxiti (moxetumomab pasudotox-tdfk) was approved for the treatment of adult patients with relapsed or refractory hairy cell leukemia who have received at least two prior systemic therapies, including treatment with a purine nucleoside analog. Lumoxiti is manufactured by AstraZeneca Pharmaceuticals.
Approximately 10 percent of individuals will not respond to treatment with chemotherapy drugs. In addition, some individuals cannot take such drugs. In such cases, individuals may be treated with biological therapies such as alpha interferon. Biologic therapies attempt to use the body’s immune system directly or indirectly to treat the malignancy.
The orphan drug alpha interferon has been approved by the FDA for use in the treatment of hairy cell leukemia. The drug is manufactured by Hoffman-LaRoche and Schering Plough. Interferon is a hormone naturally produced by the body to fight viral infections. Treatment with alpha interferon may include daily injections for up to six months, followed by maintenance injections three times weekly. Side effects mimic flu-like symptoms, which diminish over time.
A biological therapy known as rituximab (Rituxan©) has been used to treat individuals with hairy cell leukemia who do not respond to conventional therapy. Rituximab is an antibody that attaches itself to hairy cells. The drug has been approved for non-Hodgkin’s lymphoma and is being studied to determine its long-term safety and effectiveness as a therapy for hairy cell leukemia.
Interleukin-2 has been used on an experimental basis to restore natural killer cell activity in hairy cell leukemia.
The drug deoxycoformycin is being used in clinical trials on patients with hairy cell leukemia. Information about obtaining this drug can be located through the Comprehensive Cancer Center (Dr. Eric Kraut), Ohio State University, Columbus, Ohio, or the Investigational Drug Branch of the National Cancer Institute in Bethesda, Maryland.
Most patients with hairy cell leukemia carry a BRAF gene mutation, and these gene mutations have also been identified in melanoma and other cancers. Vemurafenib, a drug that targets the effects of BRAF mutations, is FDA approved for the treatment of melanoma. Responses to vemurafenib have been described in patients with hairy cell leukemia, and clinical trials are evaluating BRAF inhibition in this condition.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government website.
For information about clinical trials being conducted at the National Institutes of Health (NIH) in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
Some current clinical trials also are posted on the following page on the NORD website:
For information about clinical trials sponsored by private sources, contact:
For information about clinical trials conducted in Europe, contact:
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