Hairy cell leukemia

Hairy cell leukemia is a type of chronic lymphoid leukemia. It is uncommon, representing about 2% of all leukemias, or less than 1000 new cases diagnosed each year in the United States. Originally known as leukemic reticuloendotheliosis, hairy cell leukemia was first described by Bertha Bouroncle, M.D. and her colleagues at the OSU College of Medicine and Public Health at The Ohio State University in 1958.

Most patients are white males over the age of 40, although it has been diagnosed in teenagers. Men are four to five times more likely to develop hairy cell leukemia than women It does not appear to be hereditary, although occasional familial cases have been reported ^*." target="_blank" > Farming and gardening appear to increase the risk[http://cat.inist.fr/?aModele=afficheN&cpsidt=11083509 in some studies.

Two variants have been described: Hairy cell leukemia-variant^*, which usually is diagnosed in older men (median age above 70), and a Japanese variant. The non-Japanese variant is more difficult to treat than either 'classic' HCL or the Japanese variant HCL.

Symptoms

Patients usually present with infection, anemia, and/or easy bleeding. Some of the leukemic cells may gather in the spleen and cause it to swell. Symptoms are often vague, such as "persistent fatigue" or "not feeling well."

Hairy cell leukemia is commonly diagnosed after a routine blood count shows unexpectedly low numbers for one or more kinds of blood cells, or after unexplained bruises or unexplained infections, such as repeated bouts of pneumonia in an apparently healthy patient.

Patients with a high tumor burden may also have somewhat reduced levels of cholesterol^*

Diagnosis

Abnormal white blood cells bearing hair-like projections from the cytoplasm are seen on blood film examination or bone marrow biopsy, hence the name. The diagnosis can be confirmed by viewing the cells with a special stain, known as TRAP, or tartrate-resistant acid phosphatase.

It is also possible to definitively diagnose hairy cell leukemia through a flow cytometry blood test which identifies characteristic proteins on the cell surfaces. These cancerous cells are larger than normal and positive for CD19, CD20, CD22, CD11c, CD25, CD103, and FMC7.^* Hairy cell leukemia-variant, which shares some characteristics with B cell prolymphocytic leukemia, does not show CD25.

Treatment

Several treatments are available, and successful control of the disease is common. Treatment is usually given when the symptoms of the disease interfere with the patient's everyday life, or when white blood cell or platelet counts decline to dangerously low levels. Not all patients need treatment immediately upon diagnosis, and about 10% of patients will never need treatment.

First-line therapy: purine analog chemotherapy

Cladribine (2CDA) and pentostatin (DCF) are the two most common first-line therapies. Cladribine is a kind of mild chemotherapy which can be administered by injection under the skin, by infusion over a couple of hours into a vein, or by a pump worn by the patient that provides a slow drip into a vein, 24 hours a day for 7 days. Most patients receive cladribine by IV infusion once a day for five to seven days, but more patients are being given the option of taking this drug once a week for six weeks. Relatively few patients have significant side effects other than fatigue and a high fever caused by the cancer cells dying.

Pentostatin is chemically similar to cladribine, and has a similar success rate and side effect profile, but it is always given over a much longer period of time, usually one dose by IV infusion every two weeks for three to six months.

(A third related chemical, fludarabine, is not effective for hairy cell leukemia, despite being chemically similar.)

During the weeks following treatment the patient's immune system is severely weakened, but his bone marrow will begin to produce normal blood cells again. Treatment often results in long-term remission. About 85% of patients benefit significantly from treatment with either cladribine or pentostatin, although there is no permanent cure for this disease. If the cancer cells return, the treatment may be repeated and should again result in remission. Remission lengths vary significantly, from one year to more than twenty years.

Second-line therapy: immunotherapy

If a patient is resistant to cladribine or pentostatin, then second-line therapy of is pursued. The most common treatment for cladribine-resistant disease is infusing monoclonal antibodies which destroy cancerous B cells. Rituximab is by far the most commonly used. Most patients receive one IV infusion over several hours each week for four weeks. Its major side effect is allergic reactions, which can be severe, especially on the first infusion. Consequently, the first dose is always given in a hospital setting, although subsequent infusions may be given in a physician's office.

Other B cell-destroying monoclonal antibodies such as Alemtuzumab, Ibritumomab tiuxetan and Bexxar may be considered for refractory cases.

Two immunotoxin drugs are in trials at the NIH's National Cancer Institute in the U.S.: BL22 and LMB-2. Both of these combine part of an anti-B cell antibody with a bacterial toxin to kill the cells on internalization. BL22 attacks a common protein called CD22, which is present on hairy cells and healthy B cells. LMB-2 attacks a protein called CD25, which is not present in HCL-variant, so LMB-2 is only useful for patients with HCL-classic or the Japanese variant.

Interferon-alpha is an immune system hormone which is very helpful to a relatively small number of patients. Some patients tolerate IFN-alpha well and need to continue taking it for the drug to be successful. Other patients are able to achieve a sustained clinical remission after taking this drug for a shorter period of time. Interferon-alpha is considered the drug of choice for pregnant women with active HCL.

Other treatment options

Splenectomy can produce long-term remissions in patients whose spleens seem to be heavily involved, but its success rate is noticeably lower than cladribine or pentostatin.

Bone marrow transplants are usually shunned in this highly treatable disease because of the inherent risks in the procedure. They may be considered for refractory cases in younger, otherwise healthy individuals.

Patients with anemia or thrombocytopenia may also receive red blood cells and platelets through blood transfusions. Blood transfusions are always irradiated to remove white blood cells and thereby reduce the risk of graft-versus-host disease.

Prognosis

With appropriate treatment, the projected lifespan for patients is normal or near-normal. The first two years after diagnosis are the highest risk for fatal outcome; generally, surviving five years predicts good control of the disease. After five years' clinical remission, patients with normal blood counts can often qualify for private life insurance with some companies.^*

Patients will require lifelong monitoring and should be aware that the disease can recur without warning.

Accurately measuring survival for patients with the variant form of the disease is complicated by the relatively high median age at diagnosis. However, HCL-V patients routinely survive for more than 10 years, and younger patients can likely expect a long life.

Follow-Up Care

People who have hairy cell leukemia are never considered 'cured' and should have regular follow-up examinations after their treatment is over. Most physicians insist on seeing patients at least once a year for the rest of the patient's life, and getting blood counts twice a year. Regular follow-up care ensures that patients are carefully monitored, any changes in health are discussed, and new or recurrent cancer can be detected and treated as soon as possible. Between regularly scheduled appointments, people who have hairy cell leukemia should report any health problems, especially viral or bacterial infections, as soon as they appear.

External links

Blood disorders | Types of cancer

Haarzellleukämie | tricoleucemia

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