Acute Leukemia

Acute leukemia begins as a malignant proliferation of white blood cell (WBC) precursors, or blasts, in bone marrow or lymph tissue. It results in an accumulation of these cells in peripheral blood, bone marrow, and body tissues.

The most common forms of acute leukemia include acute lymphoblastic (lymphocytic) leukemia (ALL), characterized by abnormal growth of lymphocyte precursors (lymphoblasts); acute myeloblastic (myelogenous) leukemia (AML), which causes rapid accumulation of myeloid precursors (myeloblasts); and acute monoblastic (monocytic) leukemia, or Schilling's type, which results in a marked increase in monocyte precursors (monoblasts). Other variants include acute myelomonocytic leukemia and acute erythroleukemia.

The disease is more common in males than in females, in whites (especially those of Jewish ancestry), in children between ages 2 and 5 (80% of all leukemias in this age-group are ALL), and in those who live in urban and industrialized areas. Among children, acute leukemia is the most common form of cancer.

Untreated, acute leukemia is invariably fatal, usually because of complications resulting from leukemic cell infiltration of bone marrow or vital organs. With treatment, the prognosis varies.

In ALL, treatment induces remissions in 90% of children (average survival time: 5 years) and in 65% of adults (average survival time: 1 to 2 years). Children between ages 2 and 8 have the best survival rate - about 50% - with intensive therapy.

In AML, the average survival time is only 1 year after diagnosis, even with aggressive treatment. Remissions lasting 2 to 10 months occur in 50% of children; adults survive only about 1 year after diagnosis, even with treatment.

Causes

The exact cause of acute leukemia is unknown; however, some factors that markedly increase the chance for a person to get leukemia are well documented. "Primary" leukemia means it is the first blood cancer detected; "Secondary" leukemia arises after treatment for some other cancer. Secondary leukemia is usually AML and develops an average of 5 years after treatment of another cancer. It is especially seen after treatment for Hodgkin's Disease, myeloma, lymphoma, breast or ovarian cancer. The more aggressive the the, the more likely later AML will occur.

Signs and Symptoms

Symptoms of leukemia are associated with the impaired production and function of these components such as:

• Abdominal Swelling
• Tiredness
• Easy Bruising or Hemorrhage
• Recurrent fevers
• Bone Pain is especially seen in ALL in children
• Weight loss

The duration of symptoms prior to diagnosis can last from days to months because of the non-specific nature of the symptoms that can mimic other more common childhood illness.

Diagnostic tests 

Bone marrow aspiration showing a proliferation of immature WBCs confirms acute leukemia. If the aspirate is dry or free of leukemic cells but the patient has other typical signs of leukemia, a bone marrow biopsy - usually of the posterior superior iliac spine-must be performed.

Blood counts show thrombocytopenia and neutropenia, and a WBC differential determines the cell type. Lumbar puncture detects meningeal involvement. A computed tomography scan shows the affected organs, and cerebrospinal fluid analysis detects abnormal WBC invasion of the central nervous system.

Treatment

Systemic chemotherapy aims to eradicate leukemic cells and induce remission. It's used when fewer than 5% of blast cells in the marrow and peripheral blood are normal. The specific chemotherapeutic and radiation treatment varies with the diagnosis:

• For meningeal infiltration, the patient receives an intrathecal instillation of methotrexate or cytarabine with cranial radiation.
• For ALL, the treatment is vincristine, prednisone, high-dose cytarabine, and daunorubicin. Because ALL carries a 40% risk of meningeal infiltration, the patient also receives intrathecal methotrexate or cytarabine. If brain or testicular infiltration has occurred, me patient also needs radiation therapy.
• For AML. treatment consists of a combination of l.V. daunorubicin and cytarabine. If these fail to induce remission, treatment involves some or all of the following: a combination of cyclophosphamide, vincristine. prednisone, or methotrexate; high-dose cytarabine alone or with other drugs; amsacrine; etoposide; and 5-azacytidine and mitoxantrone.
• For acute monoblastic leukemia, the patient receives cytarabine and thioguanine with daunorubicin or doxorubicin.

Treatment may also include antibiotic, antifungal, and antiviral drugs and granulocyte injections to control infection, as well as transfusions of platelets to prevent bleeding and of red blood cells to prevent anemia. Bone marrow transplantation is performed in some patients.

Prevention

Because the cause of most cases is unknown, prevention of most cases is not possible. Minimizing exposure to toxins, radiation, chemicals, etc. may reduce risk.