Leukemia

Risk: Risk factors for leukemia include exposure to high levels of radiation (such as a nuclear event or massive doses of radiation treatment, but not diagnostic x-rays or radiation from electromagnetic fields) and to chemical or environmental carcinogens such as benzene, formaldehyde, petrochemicals, or previous chemotherapy. Most cases of leukemia develop, however, with no known link to a risk factor.

CLL primarily affects middle-aged to elderly adults. ALL typically develops in adults between the ages of 30 and 60. CML primarily affects middle-aged adults. Regardless of type, leukemia affects males at twice the rate of females.

Incidence and Prevalence: Leukemia is diagnosed in 8 to 10 individuals per 100,000 each year. AML accounts for 46% of leukemias. About 10,600 new cases are diagnosed annually.

CML represents 14% of leukemias or about 4,400 new cases a year. ALL accounts for 11% of leukemias; about 3,800 new cases are diagnosed each year. CLL makes up 29% of leukemias with between 7,500 and 12,500 new cases diagnosed in the US each year (Cheson 2536).

History: In acute leukemia, symptoms appear and get worse quickly. Individuals with this disease go to their doctor because they feel sick. They may have noticed general symptoms, such as weight loss, loss of appetite, frequent infection, headache, dizziness, or fatigue. In chronic leukemia, symptoms may not appear for a long time and when they do appear, they are generally mild at first and worsen gradually. Chronic leukemia is generally discovered during a routine checkup before there are any symptoms. Symptoms may include fever, chills, and other flu-like symptoms; weakness and fatigue; frequent infections; generally feeling ill (malaise); vomiting; loss of appetite; easy bleeding and bruising; severe nosebleeds and swollen or bleeding gums; weight loss; shortness of breath; bone and joint pain; blurred vision and difficulty maintaining balance; seizures; abdominal pain; and/or night sweats.

Physical exam: Individuals may present with enlarged and tender lymph nodes most often in the underarms, groin, or neck areas; an enlarged liver and/or spleen; gum enlargement, tiny pinpoint red spots (petechiae) or larger purple discolorations (purpura) under the skin, and fever. Individuals may appear pale if anemia has developed. If anemia is present, the reduced numbers of red blood cells may cause shortness of breath due to low oxygen content in the blood.

Tests: Although blood tests may reveal that an individual has leukemia, they may or may not show what type of leukemia it is. A complete blood count (CBC) with differential (peripheral blood smear) will show abnormalities consistent with leukemia, including the number, appearance, and maturity of WBCs. The number of cells that are blasts (immature white blood cells) is especially important to diagnosis; if more than one-third of cells are blasts, this confirms a diagnosis of acute leukemia. The hemoglobin, hematocrit, and platelet count may be decreased. Blood chemistries will also be performed to help determine related liver or kidney problems and to serve as a baseline for comparison during eventual treatment.

A sample of bone marrow liquid is removed with a needle (bone marrow aspiration) and examined under the microscope. A bone marrow biopsy, performed with a larger needle, involves removing a small piece of bone and bone marrow together. Both bone marrow aspiration and bone marrow biopsy can tell what type of leukemia the person has. If leukemia cells are found in the bone marrow sample, a spinal tap (lumbar puncture) may be performed to check for leukemia cells in the fluid that fills the spaces in and around the brain and spinal cord (cerebrospinal fluid). Chest x-rays can reveal signs of the disease in the chest. Cytochemistry techniques are used to examine cells microscopically after they have been colored using special stains. By highlighting cell characteristics, such as granules or abnormal shapes and sizes, specific types of WBCs can be identified in peripheral blood, bone marrow, spinal fluid and lymph gland samples to help confirm the diagnosis.

Flow cytometry may also be used to examine cells obtained from the blood, the bone marrow, or lymph glands. This technique treats cells with certain antibodies and examines them with laser beams. Because each antibody only sticks to certain types of cells, the method provides very accurate determination of the type of leukemia.

Chromosome studies (cytogenetic studies) provide further information. A variety of acquired chromosome abnormalities are associated with the diagnosis and prognosis of leukemia. For example, up to 95% of individuals with CML have an exchange between chromosomes 9 and 22. This exchange produces the "Philadelphia chromosome." This finding helps in the diagnosis of CML. ALL may be confirmed by DNA studies, since all of the cells in this leukemia are abnormal lymphocytes with the same characteristics, which are recorded on the person's DNA.

Imaging studies such as CT scanning (computed tomography) may be used only to evaluate lymph gland involvement and organs that may be affected. Ultrasound is also sometimes used to visualize changes in the kidneys, liver, or spleen. In types of leukemia in which the lymph glands may be affected, such as CLL, biopsies of lymph nodes may be done to examine lymph cells.