Hairy cell leukemia is a rare, slow-growing cancer of the blood in which the bone marrow produces too many B cells (lymphocytes), a type of white blood cell that fights infection. The condition is named after these excess B cells which look 'hairy' under a microscope because of fine projections (villi) from their surface. As the number of leukemia cells increases, fewer healthy white blood cells, red blood cells and platelets are produced.
Hairy cell leukemia affects more men than women, and it occurs most commonly in middle-aged or older adults. Hairy cell leukemia is considered a chronic disease because it may never completely disappear, although treatment can lead to a remission for years.
Some people show no signs or symptoms of hairy cell leukemia, but a blood test for another disease or condition may inadvertently reveal hairy cell leukemia in their blood. Other times people with hairy cell leukemia experience signs and symptoms common to a number of diseases and conditions, such as:
- A feeling of fullness in your abdomen that may make it uncomfortable to eat more than a little at a time
- Easy bruising
- Recurring infections
- Weight loss
The underlying cause of this condition is unknown. Cancers are caused by a defect in your DNA. In the case of hairy cell leukemia, mutations in the DNA cause your bone marrow stem cells to create too many white blood cells that don't work properly. It is not clear what causes the DNA mutations that lead to hairy cell leukemia.
Certain factors may increase your risk of developing hairy cell leukemia. Not all research studies agree on what factors increase your risk of the disease.
Some research indicates that your risk of hairy cell leukemia increases based on your:
- Exposure to radiation. People exposed to radiation, such as those who work around X-ray machines or those who received radiation treatment for cancer, may have a higher risk of developing hairy cell leukemia, but the evidence is inconclusive.
- Exposure to chemicals. Industrial and agricultural chemicals could play a role in hairy cell leukemia development. However, some studies have found this not to be the case.
- Exposure to sawdust. Some studies have found a link between working with wood and sawdust and an increased risk of hairy cell leukemia. But this connection hasn't been proved conclusively.
- Ethnicity. Hairy cell leukemia affects men of Ashkenazi Jewish ancestry more frequently than men of other ethnic groups.
The cause of this disease is unknown, no effective preventive measures can be taken. The disease is rare, routine screening is not cost-effective.
To diagnose hairy cell leukemia, your doctor may recommend tests and procedures that include:
- Physical exam. By feeling your spleen — an oval-shaped organ on the left side of your upper abdomen — your doctor can determine if it's enlarged. An enlarged spleen may cause a sensation of fullness in your abdomen that makes it uncomfortable to eat.
- Blood tests. The complete blood count, to monitor the levels of blood cells in your blood. People with hairy cell leukemia have low levels of all three types of blood cells — red blood cells, white blood cells and platelets. Another blood test called a peripheral blood smear looks for hairy cell leukemia cells in a sample of your blood.
- Bone marrow biopsy. During a bone marrow biopsy, a small amount of bone marrow is removed from your hip area. This sample is used to look for hairy cell leukemia cells and to monitor your healthy blood cells.
- Computerized tomography (CT) scan. A CT scan shows detailed images of the inside of your body. Your doctor may order a CT scan to detect enlargement of your spleen and your lymph nodes.
More than 95% of new patients are treated well or at least adequately by cladribine or pentostatin. A majority of new patients can expect a disease-free remission time span of about ten years, or sometimes much longer after taking one of these drugs just once. If re-treatment is necessary in the future, the drugs are normally effective again, although the average length of remission is somewhat shorter in subsequent treatments.
As with B-cell chronic lymphocytic leukemia, mutations in the IGHV on hairy cells are associated with better responses to initial treatments and with prolonged survival.
How soon after treatment a patient feels "normal" again depends on several factors, including:
- How advanced the disease was at the time of treatment
- The patient's underlying health status
- Whether the patient had a "complete response" or only a partial response to the treatment
- Whether the patient experienced any of the rare, but serious side effects such as kidney failure
- How aggressive the individual's disease is
- Whether the patient is experiencing unusual psychological trauma from the "cancer" diagnosis
- How the patient perceived his or her pre-treatment energy level and daily functioning
With appropriate treatment, the overall projected lifespan for patients is normal or near-normal. In all patients, the first two years after diagnosis have the highest risk for fatal outcome; generally, surviving five years predicts good control of the disease. After five years' clinical remission, patients in the United states with normal blood counts can often qualify for private life insurance with some US companies.
Accurately measuring survival for patients with the variant form of the disease (HCL-V) is complicated by the relatively high median age (70 years old) at diagnosis. However, HCL-V patients routinely survive for more than 10 years, and younger patients can likely expect a long life.
Worldwide, approximately 300 HCL patients per year are expected to die. Some of these patients were diagnosed with HCL due to a serious illness that prevented them from receiving initial treatment in time; many others died after living a normal lifespan and experiencing years of good control of the disease. Perhaps as many as five out of six HCL patients die from some other cause.
Despite decade-long remissions and years of living very normal lives after treatment, hairy cell leukemia is officially considered an incurable disease. While survivors of solid tumors are commonly declared to be permanently cured after two, three, or five years, people who have hairy cell leukemia are never considered 'cured'. Relapses of HCL have happened even after more than twenty years of continuous remission. Patients will require lifelong monitoring and should be aware that the disease can recur even after decades of good health.
People in remission need 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 about 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.
HCL patients are also at a slightly higher than average risk for developing a second kind of cancer, such as colon cancer or lung cancer, at some point during their lives (including before their HCL diagnosis). This appears to relate best to the number of hairy cells, and not to different forms of treatment. On average, patients might reasonably expect to have as much as double the risk of developing another cancer, with a peak about two years after HCL diagnosis and falling steadily after that, assuming that the HCL was successfully treated. Aggressive surveillance and prevention efforts are generally warranted, although the lifetime odds of developing a second cancer after HCL diagnosis are still less than 50%.
- Cladribine (Leustatin (injection)) - FDA-approved indication: Treatment of hairy cell leukemia.
- Pentostatin for injection (Nipent) - FDA-approved indication: Single agent treatment for adult patients with alpha-interferon-refractory hairy cell leukemia.
- Refer to Research Publications.