Leukemia

Peripheral blood smear showing chronic lymphocytic leukemia(Acute Lymphocytic Leukemia, Acute Myelogenous Leukemia, Chronic Lymphocytic Leukemia, Chronic Myelogenous Leukemia)

– An acute or chronic cancer involving the blood-forming tissues in the bone marrow. It may be classified as myeloid or lymphoid.

Causes and Incidence

The cause of the various leukemias is unclear, although a viral association is suspected in some types. Exposure to certain toxins (e.g., benzene, ionizing radiation) has been implicated, as have genetic defects and a genetic predisposition. Leukemia accounts for 3% of all cancers diagnosed in the United States each year, and about 16,000 people die annually of some form of leukemia. Acute lymphocytic leukemia (ALL) is most common in children 3 to 5 years of age. However, it also accounts for 20% of diagnosed adult leukemias. Acute myelogenous leukemia (AML) is an adult disease with a median age at onset of 50 years. Chronic myelogenous leukemia (CML) occurs between the ages of 20 and 60, with a peak incidence between 50 and 60 years of age. Chronic lymphocytic leukemia (CLL) is the most common leukemia in the United States, accounting for 30% of cases diagnosed each year. The median age of onset is 60 years, and it occurs twice as often in men as in women.

Disease Process

Whatever the etiologic agent, a transformation of leukocytes and leukocyte precursors into malignant cells occurs. Large numbers of these immature, abnormal cells proliferate rapidly, accumulating in the bone marrow, replacing the normal cells, and suppressing normal hematopoiesis. Proliferation also occurs in the lymph nodes, liver, and spleen. Eventually all body organs are involved in the leukemic process.

Symptoms

Acute forms of the disease are more rapidly progressive than chronic forms, and acute cell forms are less mature and predominantly undifferentiated.

ALL
Fatigue; dyspnea on exertion; anorexia; weight loss; headache; swollen cervical lymph nodes; swollen, painful joints; splenomegaly; about 10% of cases are asymptomatic

AML
Fatigue, dyspnea on exertion, anorexia, weight loss, headache, swollen cervical lymph nodes, recurrent infections unresponsive to standard treatment, easy bruising, epistaxis, gingivitis

CML
Often asymptomatic for a period of time; then, insidious onset of nonspecific symptoms (fatigue, dyspnea, anorexia, weight loss, fever, night sweats); finally, splenomegaly, pallor, bleeding, and marked lymphadenopathy

CLL
Insidious, asymptomatic onset with lymphadenopathy, then fatigue, anorexia, weight loss, and dyspnea; anemia, thrombocytopenia, and bacterial, viral, and fungal infections are present in advanced disease

Potential Complications

The prognosis is better among individuals with acute forms of leukemia and for those who experience total remission after the first course of treatment. Children have a better survival rate than adults. People with CLL are most likely to develop second malignancies, and people with CML have the shortest survival rates, often dying of a blast crisis. Other complications of leukemia include infection, hemorrhage, organ failure, and recurrence of the disease.

Diagnostic Tests

The leukocyte count is elevated, from 15,000 to 500,000/mm3 or higher; a large number of immature neutrophils are present; bone marrow biopsy shows a massive number of WBCs in the blast phase; and RBCs, hemoglobin, and hematocrit are decreased. Tumor markers aid in distinguishing the type of leukemia.

Treatments

Surgery
None.

Drugs
Chemotherapy to induce remission, consolidation or maintenance chemotherapy after remission in acute leukemias; chemotherapy in stage III CLL cases; chemotherapy in CML before bone marrow transplantation.

General
Radiation for palliation or as a pretreatment for bone marrow transplantation; transfusions, reverse isolation procedures; antibiotics to treat secondary infection; bone marrow transplantation is the only curative modality in CML and is used after relapse in acute leukemias.