CHRONIC LYMPHOCYTIC LEUKEMIA (CLL)
CLL is a common malignancy of older adults; two thirds of all patients are older than 60 years of age at diagnosis. It is the most common form of leukemia in the United States and Europe, affecting more than 120,000 people, but is rarely seen in Asia. The average survival time for patients with CLL ranges from 14 years (early stage) to 2.5 years (late stage).
CLL typically derives from a malignant clone of B lymphocytes (T-lymphocyte CLL is rare). In contrast to the acute forms of leukemia, most of the leukemia cells in CLL are fully mature. It appears that these cells can escape apoptosis (programmed cell death), with the result being an excessive accumulation of the cells in the marrow and circulation. The antigen CD52 is preva-lent on the surface of many of these leukemic B cells. The disease is classified into three or four stages (two classification systems are in use). In the early stage, an elevated lymphocyte count is seen and can exceed 100,000/mm3. Because the lymphocytes are small, they can easily travel through the small capillaries within the circulation, and the pulmonary and cerebral complications of leukocytosis (as seen with myeloid leukemias) typically are not found in CLL.
Lymphadenopathy occurs as the lymphocytes are trapped within the lymph nodes. The nodes can become very large and are sometimes painful. Hepatomegaly and splenomegaly then develop.
In later stages, anemia and thrombocytopenia may develop. Treatment is typically initiated in the later stages; earlier treatment does not appear to increase survival. Autoimmune complications can also occur at any stage, as either autoimmune hemolytic anemia or idiopathic thrombocytopenic purpura (ITP). In the autoimmune process, the RES destroys the body’s own RBCs or platelets.
Many patients are asymptomatic and are diagnosed incidentally during routine physical examinations or during the course of treatment for another disease. An increased lymphocyte count (lymphocytosis) is always present. The RBC and platelet counts may be normal or, in later stages of the illness, decreased. En-largement of lymph nodes (lymphadenopathy) is common; it can be severe and sometimes painful. The spleen can also be enlarged (splenomegaly).
Patients with CLL can develop “B symptoms,” a constellation of symptoms including fevers, drenching sweating (especially at night), and unintentional weight loss. These patients have defects in their humoral and cell-mediated immune systems; therefore, infections are common. The defect in cellular immunity is evi-denced by an absent or decreased reaction to skin sensitivity tests (eg, Candida, mumps), which is known as anergy. Problems with life-threatening infections are common. Viral infections, such as herpes zoster, can become widely disseminated.
In early stages, CLL may require no treatment. When symptoms are severe (drenching night sweats, painful lymphadenopathy), or when the disease progresses to later stages (with resultant anemia and thrombocytopenia), chemotherapy with corticosteroids and chlorambucil (Leukeran) is often used. Other useful agents in-clude cyclophosphamide (eg, Cytoxan), vincristine (eg, Oncovin), and doxorubicin (eg, Adriamycin). A significant number of pa-tients who do not respond to these medications have achieved re-mission with fludarabine (Fludara), and this medication is increasingly being used as front-line therapy. The major side ef-fect of fludarabine is prolonged bone marrow suppression, mani-fested by prolonged periods of neutropenia, lymphopenia, and thrombocytopenia. Patients are then at risk for such infections as Pneumocystis carinii, Listeria, mycobacteria, herpes viruses, andcytomegalovirus (CMV). The monoclonal antibody rituximab (Rituxan) also has efficacy in CLL therapy. It is often used in com-bination with other chemotherapeutic medications. Research has shown that the monoclonal antibody alemtuzumab (Campath) targets the CD52 antigen commonly found on CLL cells and that it is effective in clearing the marrow and circulation of these cells without affecting the stem cells. Because CD52 is present on both B and T lymphocytes, patients receiving alemtuzumab are at sig-nificant risk for infection; prophylactic use of antiviral agents and antibiotics (eg, trimethoprim and sulfamethoxazole [Septra]) is important and needs to continue for a minimum of 2 months after the patient stops treatment. Because bacterial infections are com-mon in patients with CLL, intravenous treatment with immuno-globulin may be given to selected patients.
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