Leukemia

Leukemia is a type of cancer of the blood and bone marrow; it is a general term used to describe a wide range of conditions, the common feature of which is elevated levels of immature white blood cells.  The word leukemia in fact means 'white blood'.

Leukemia has various subtypes, the main distinction being between acute leukemia and chronic leukemia.  Acute leukemia involves a rapid increase in the number of immature white blood cells and requires immediate treatment due to the rapid proliferation of malignant cells that spread throughout the body.  Chronic leukemia involves excess build up of more mature abnormal white blood cells.  It progresses much more slowly than the acute form (months to years), giving doctors time to monitor the disease and decide on the most appropriate treatment.

Within the subtypes of acute or chronic, leukemia is divided into two further subtypes based on the type of blood cell that is affected: lymphocytic or myeloid/myelogenous leukemia.

These subtypes give rise to the four main types of leukemia:

• Acute lymphoblastic leukemia (ALL)
• Chronic lymphocytic leukemia (CLL)
• Acute myelogenous leukemia (AML)
• Chronic myelogenous leukemia (CML)

Other, rarer subtypes of leukemia include Hairy Cell Leukemia (HCL), T-cell Prolymphocytic Leukemia (T-PLL), Large Granular Lymphocytic Leukemia, Adult T-cell Leukemia (caused by an HIV-like virus, HTLV), Acute Eosinophilic Leukemia (AEL), Chronic Eosinophilic Leukemia (CEL).

Incidence; Causes and Development; Contributing Risk Factors

Most (90%) leukemias are diagnosed in adults.  For the main subtypes of leukemia:

• Acute lymphoblastic leukemia (ALL): More common in young children and those over the age of 65.
• Chronic lymphocytic leukemia (CLL): Usually affects those over the age of 55, twice as many men as women, and almost never affects children.
• Acute myelogenous leukemia (AML): More common in adults and men than in children and women.
• Chronic myelogenous leukemia (CML): Occurs mainly in adults and men, with fewer children and women affected.

The cause of leukemia is unknown, but hereditary factors do play a role.

Some industrial chemicals, such as benzene, may be associated with increased risk of leukemia, as can prolonged exposure to X-rays, or other radiation that is used in cancer treatment or CT scans for example.  Some medications used in chemotherapy also carry some risk.

Signs and Symptoms

Due to leukemia's effect of impairing blood clotting, patients may develop 'pinprick' bleeds, showing up as small (1-2mm) red or purple patches on the skin, caused by broken capillary blood vessels.

See more signs and symptoms listed below.

Diagnosis and Tests

Diagnosis of leukemia involves examination of the number of red cells, platelets, and different types of white cells in the blood, which can show a harmful imbalance if leukemia is present.  In most patients, leukemia produces high numbers of extra white blood cells, many of which are immature or dysfunctional.  This can readily be seen under a microscope.

If leukemia is suspected then the next step is bone marrow aspiration or biopsy.

Following a diagnosis, blood chemistries are used to gauge the degree of liver and kidney damage and the effects of any chemotherapy treatment.

Treatment and Prevention

Treatment depends on the type of leukemia present:

• Acute lymphoblastic leukemia (ALL): Usually treated with chemotherapy and radiotherapy, corticosteroids, bone marrow transplant
• Chronic lymphocytic leukemia (CLL): Incurable, but many effective treatments including radiotherapy, corticosteroids, splenectomy
• Acute myelogenous leukemia (AML): Chemotherapy, bone marrow transplant
• Chronic myelogenous leukemia (CML): Treated with specific drugs, radiotherapy, corticosteroids, bone marrow transplant, interferon
• Hairy cell leukemia (HCL): Interferon, splenectomy

For all types of leukemia, transfusions of red blood cells or platelets help to maintain adequate levels.  Analgesics, antibiotics or antifungal medications are also used as required.

To help prevent leukemia, limit exposure to toxic chemicals, as well as to X-rays and other forms of radiation.

Prognosis

Survival rates depend on the type of leukemia:

• Acute lymphoblastic leukemia (ALL): 85% of children and 50% of adults survive
• Chronic lymphocytic leukemia (CLL): 75% of sufferers survive longer than 5 years
• Acute myelogenous leukemia (AML): Only 40% of sufferers survive longer than 5 years
• Chronic myelogenous leukemia (CML): 90% of sufferers survive longer than 5 years