Hairy cell leukemia (HCL) is a type of chronic leukemia that affects B lymphocytes, which are specialized white blood cells that produce antibodies to fight infection and disease. These abnormal B lymphocytes develop tiny “hair-like” projections on their surface, which give the cancer its name. These leukemia cells accumulate in the bone marrow, liver and spleen.
In the past, HCL was often fatal and was usually diagnosed on the basis of a very low blood count, called the complete blood count (CBC). Today, thanks to pioneering treatment developed at OSUCCC – James, many patients with this cancer go into remission for years with the help of effective treatments.
A CBC test can help identify very low levels of red and white blood cells as well as platelets, which are important for clotting blood. A bone marrow biopsy can also be done to check for the presence of hairy cells in the bone marrow.
If the CBC is very low, a transfusion of red blood cells, or anemia, may be needed. If the platelet count is very low, patients may notice bruising, nosebleeds or bleeding in the gums. Some people with this cancer develop an enlarged spleen that can become two to three times its normal size. The doctor can feel this enlargement during a physical exam and may order an abdominal CT scan or ultrasound. The enlarged spleen can also cause pain on the left side of the abdomen and an early feeling of fullness during meals.
In most cases, doctors will start treatment with a chemotherapy drug called cladribine. It works by killing the hairy cells without harming healthy ones. This form of treatment typically achieves a complete remission in 85 percent of patients. It is very rare for hairy cell leukemia to return after a period of remission. However, the hematologists at NYU Langone have found ways to improve the likelihood that a patient will achieve and maintain remission with this type of therapy.
For the 10 percent of patients with hairy cell leukemia who do not achieve a complete remission with cladribine, another type of chemotherapy, called pentostatin or a chemo-immunotherapy drug, may be used to treat them. These therapies are less toxic than cladribine and have more predictable outcomes. They may allow these patients to achieve a complete response with a longer duration of remission than those who do not respond to cladribine.
If treatment is successful, a bone marrow biopsy will be done to make sure that all of the abnormal cells have been eliminated. It is not uncommon for a small number of hairy cells to be detected, even after the patient has achieved a complete response, in which case the doctor will consider the patient’s condition to be minimal residual disease (MRD). This means that there are still some hairy leukemia cells remaining, but they cannot be seen under the microscope. Some of these patients are candidates for a different therapy, such as rituximab or moxetumomab pasudotox.
