Aggressive NK-cell leukemia

Natural killer (NK) cells are a type of lymphocyte (called large granular lymphocytes) that attacks foreign cells. They are often the body’s first line of defence against infection.

Aggressive NK-cell leukemia (also called aggressive NK-cell lymphoma, or ANKL, is a very rare type of NHL. The body makes large numbers of NK cells that are larger than normal. It is grouped with T-cell lymphomas.

ANKL develops most often in people from Asia, Central America and South America. Doctors don’t know the exact cause of ANKL, but it has a strong link with the Epstein-Barr virus (EBV). ANKL usually progresses quickly and often has a poor prognosis.

There is a very rare slow-growing (indolent) type of NK-cell leukemia that has a more favourable prognosis. It is called chronic NK-cell leukemia and is treated like T-cell large granular lymphocytic leukemia.

ANKL usually affects the blood and bone marrow, but it can also affect the liver or spleen. People with ANKL usually have:

• B symptoms (unexplained fever, drenching night sweats and unexplained weight loss) that develop quickly
• larger than normal liver or spleen
• lower than normal numbers of healthy blood cells (called cytopenia)
• larger than normal lymph nodes

In some cases, ANKL can cause disseminated intravascular coagulation (DIC). Different organs can also stop working, or fail. These are serious conditions that need to be treated right away.

ANKL is treated with chemotherapy. Some people may be offered a stem cell transplant.

Chemotherapy is the main treatment for ANKL.

A combination of the following chemotherapy drugs is usually given for ANKL:

• vincristine (Oncovin)
• daunorubicin (Cerubidine, daunomycin)
• doxorubicin (Adriamycin)
• cytarabine (Cytosar, Ara-C)
• methotrexate
• cyclophosphamide (Cytoxan, Procytox)

Steroids, such as prednisone or dexamethasone (Decadron, Dexasone), may be used in combination with chemotherapy.

The central nervous system (CNS) is the brain and spinal cord. There is a risk that ANKL will spread to the CNS. CNS prophylaxis is used to try to prevent lymphoma cells from entering the tissue covering the brain and spinal cord.

CNS prophylaxis or treatment may be given as intrathecal chemotherapy. This means that the chemotherapy drugs are injected into the cerebrospinal fluid (CSF).

The most common chemotherapy drugs used for CNS prophylaxis or treatment are:

• methotrexate
• cytarabine (Cytosar, Ara-C)
• a steroid such as prednisone

A stem cell transplant may be offered to some people with ANKL who respond to chemotherapy.