Leukemia

Reviewed by Dr. Clement J. Cheng

Leukemia is a broad term used to describe cancer of the blood cells. Leukemia is marked by the body’s increased production of malignant white blood cells, which hinders the body’s manufacture of red blood cells, platelets, and healthy white blood cells.

Leukemia differs from other cancers because it does not produce tumors. Instead, it is defined as the widespread overproduction of cancerous white blood cells. In fact, the word “leukemia” is from the Greek words for “white” and “blood.”

Healthy blood contains white cells to fight disease, platelets to stanch wounds, and red cells to deliver oxygen to various parts of the body. Hundreds of billions of new blood cells are produced every day in the body’s bone marrow. Most of these cells are red blood cells, but people with leukemia start producing more white blood cells than necessary. These abnormal white blood cells live longer than normal white blood cells and do not mature normally.

Leukemic white blood cells cannot fight infection like healthy white blood cells. As they multiply, they interfere with the production of healthy blood cells, which leads to a deficit of red blood cells, platelets, and normal white blood cells. Leukemia patients become anemic and susceptible to bruising, bleeding, and infection.

Acute lymphocytic leukemia (ALL) and acute granulocytic leukemia (AGL): ALL, also called childhood leukemia, develops when lymphocytes, a type of white blood cell that fights viruses and infections, reproduce rapidly in the bone marrow and blood. AGL occurs when a granulocyte, another type of white blood cell, becomes cancerous and reproduces unchecked. AGL is also called acute myelogenous leukemia (AML).

Bone marrow produces granulocytes; lymph glands and bone marrow produce lymphocytes. Granulocytes and lymphocytes normally start out as immature cells called blasts and develop into healthy, mature white blood cells. However, for people with ALL and AGL, these blasts fail to mature and start to overpopulate the bone marrow, blood, and lymph glands. As a result, the bone marrow cannot produce enough red blood cells, platelets, or healthy white blood cells.

ALL is more common in children; AGL is more common in adults. Although experts believe that it is not inherited, the exact cause is unknown.

Symptoms of ALL and AGL include:

• Flu-like feeling
  
• Fever
  
• Aching joints
  
• Fatigue
  
• Swollen lymph glands
  
• Unusually easy bleeding or bruising
  
• Anemia, if the cancer is advanced
  

Chronic granulocytic leukemia (CGL): CGL (also called CML) is the uncontrolled production of granulocytes in the bone marrow. The leukemic cells are generally more mature than in ALL or AGL, which results in the granulocyte levels rising dramatically.

CGL usually affects people over age 50. People exposed to radiation are at a slightly higher risk to develop the disease. Many people with CGL have an acquired chromosomal abnormality, the Philadelphia chromosome. This abnormality is present when portions of two different chromosomes are switched, causing rampant proliferation of white blood cells.

CGL is split into two disease phases. The first phase is relatively mild and lasts for three to five years. It is followed by a “blast transformation.” A blast transformation happens when the blood fills with blast cells, or immature white blood cells. During the second phase, the symptoms of CGL will mirror those of AGL.

Symptoms of CGL include:

• Flu-like feeling
  
• Fatigue
  
• Shortness of breath
  
• Pressure in abdomen due to enlarged spleen
  
• Night sweats
  
• Weight loss
  
• Anemia
  

Chronic lymphocytic leukemia (CLL): An excessive number of lymphocytes exist in the blood, lymph glands, spleen, and bone marrow in CLL. As the disease progresses, the malignant lymphocytes spread to other tissues. This results in the swelling of the lymph glands, the liver, and the spleen. The body becomes unable to fight infection effectively.

CLL is the most common leukemia in the United States. It mainly affects people over age 50. Most people with this type of cancer exhibit no symptoms and are diagnosed with the results of a blood test performed for another disease. Sometimes people with CLL require no treatment, and the disease will not get worse for 10 to 15 years. However, the average person with CLL will live 6 years after diagnosis. Twenty-five percent of CLL patients live for over 10 years after diagnosis and die of other causes. The earlier the diagnosis, the better the prognosis generally is.

Symptoms of CLL include:

• Flu-like feeling
  
• Fatigue
  
• Fever
  
• Swollen glands
  
• Excessive sweating
  
• Full feeling in abdomen due to enlarged spleen
  
• Weight loss
  
• Anemia
  

Environmental risks and tobacco use also heighten the risk of developing leukemia. Also, prolonged exposure to radiation, certain chemicals, and low-frequency electromagnetic fields may raise the risk.

Because it may display no obvious symptoms, leukemia is often diagnosed incidentally during a physical exam. Doctors will recognize enlarged lymph nodes, swollen gums, and an enlarged liver or spleen as symptoms. A blood test showing an abnormally high white blood cell count is usually enough for a tentative diagnosis. To confirm diagnosis, the patient will undergo a bone marrow aspiration and bone marrow biopsy from a pelvic bone. If CML is suspected, the patient will undergo tests to detect the Philadelphia chromosome.

Doctors will also perform imaging tests in some people suspected to have leukemia. These tests include X-ray, CT scan, MRI, and ultrasound.

Although the number of leukemia cases reported has remained static since the 1950s, survival rates have improved. ALL, childhood leukemia, represents a success story. Ninety percent of children diagnosed with ALL attain remission (no more cancerous cells detected) and more than half are completely cured. In the 1960s, the five-year survival rate was 4 percent; in the 1990s, it was better than 50 percent.

Adult patients with ALL have an 80 to 90 percent chance of remission. About 40 percent who reach remission survive another five years with the chance of a full cure. Patients with AML have a 60 to 70 percent chance of remission; 20 percent survive three years with the chance of a cure.

Patients with acute leukemia almost always undergo aggressive chemotherapy to attain remission. Treatment is administered for as long as it takes to attain remission.

ALL patients may gain satisfactory remission after several weeks in the hospital. To control the disease, they will receive low-dose chemotherapy and possibly radiation for a period of time to eliminate residual traces of cancer. The amount of time spent on this phase of therapy is dependent upon the individual patient.

AML does not generally respond well to chemotherapy. The best chance of a cure is bone marrow transplantation, which requires a donor with matching tissue type and genetic characteristics—usually a family member. Bone marrow transplantation can also offer a chance at remission to people with recurring cases of ALL.

CLL treatments tend to be conservative because the disease progresses so slowly. If swelling appears in the lymph nodes or other organs, oral chemotherapy can keep the disease in check for several years. Many CLL patients lead normal lives and die of other causes.

CML can be effectively treated with oral chemotherapy for several years before the disease moves to the acute stage. Interferon, a naturally occurring protein that kills or slows the growth of cancerous cells, can lengthen CML patients’ lives. Because CML inevitably advances to the acute phase, some doctors advise a bone marrow transplant during the chronic stage.