Leukemia is cancer that starts in the tissue that forms blood. To understand cancer, it helps to know how normal blood cells form.
Normal Blood Cells
Most blood cells develop from cells in the bone marrow called stem cells. Bone marrow is the soft material in the center of most bones.
White blood cells help fight infection. There are several types of white blood cells.
Red blood cells carry oxygen to tissues throughout the body.
Platelets help form blood clots that control bleeding.
White blood cells, red blood cells, and platelets are made from stem cells as the body needs them. When cells grow old or get damaged, they die, and new cells take their place.
The picture below shows how stem cells can mature into different types of white blood cells.
First, a stem cell matures into either a myeloid stem cell or a lymphoid stem cell:
- A myeloid stem cell matures into a myeloid blast. The blast can form a red blood cell, platelets, or one of several types of white blood cells.
- A lymphoid stem cell matures into a lymphoid blast. The blast can form one of several types of white blood cells, such as B cells or T cells.
The white blood cells that form from myeloid blasts are different from the white blood cells that form from lymphoid blasts.
In a person with leukemia, the bone marrow makes abnormal white blood cells. The abnormal cells are leukemia cells.
Unlike normal blood cells, leukemia cells don't die when they should. They may crowd out normal white blood cells, red blood cells, and platelets. This makes it hard for normal blood cells to do their work.
Like all blood cells, leukemia cells travel through the body. The symptoms of leukemia depend on the number of leukemia cells and where these cells collect in the body.
People with chronic leukemia may not have symptoms. The doctor may find the disease during a routine blood test.
People with acute leukemia usually go to their doctor because they feel sick. If the brain is affected, they may have headaches, vomiting, confusion, loss of muscle control, or seizures. Leukemia also can affect other parts of the body such as the digestive tract, kidneys, lungs, heart, or testes.
Common symptoms of chronic or acute leukemia may include:
- Swollen lymph nodes that usually don't hurt (especially lymph nodes in the neck or armpit).
- Fevers or night sweats.
- Frequent infections.
- Feeling weak or tired.
- Bleeding and bruising easily (bleeding gums, purplish patches in the skin, or tiny red spots under the skin).
- Swelling or discomfort in the abdomen (from a swollen spleen or liver).
- Weight loss for no known reason.
- Pain in the bones or joints.
Most often, these symptoms are not due to cancer. An infection or other health problems may also cause these symptoms. Only a doctor can tell for sure.
Anyone with these symptoms should tell the doctor so that problems can be diagnosed and treated as early as possible.
Experts say that different leukemias have different causes.
The following are either known causes, or strongly suspected causes:
- Artificial ionizing radiation.
- Viruses - HTLV-1 (human T-lymphotropic virus) and HIV (human immunodeficiency virus).
- Benzene and some petrochemicals.
- Alkylating chemotherapy agents used in previous cancers.
- Maternal fetal transmission (rare).
- Hair dyes.
- Genetic predisposition - some studies researching family history and looking at twins have indicated that some people have a higher risk of developing leukemia because of a single gene or multiple genes.
- Down syndrome - people with Down syndrome have a significantly higher risk of developing leukemia, compared to people who do not have Down syndrome. Experts say that because of this, people with certain chromosomal abnormalities may have a higher risk.
- Electromagnetic energy - studies indicate there is not enough evidence to show that ELF magnetic (not electric) fields that exist currently might cause leukemia. The IARC (International Agency for Research on Cancer) says that studies which indicate there is a risk tend to be biased and unreliable.
As the various types of leukemias affect patients differently, their treatments depend on what type of leukemia they have. The type of treatment will also depend on the patient's age and his state of health.
In order to get the most effective treatment the patient should get treatment at a center where doctors have experience and are well trained in treating leukemia patients. As treatment has improved, the aim of virtually all health care professionals should be complete remission - that the cancer goes away completely for a minimum of five years after treatment.
Treatment for patients with acute leukemias should start as soon as possible - this usually involves induction therapy with chemotherapy, and takes place in a hospital.
When a patient is in remission he will still need consolidation therapy or post induction therapy. This may involve chemotherapy, as well as a bone marrow transplant (allogeneic stem cell transplantation).
If a patient has Chronic Myelogenous Leukemia (CML) his treatment should start as soon as the diagnosis is confirmed. He will be given a drug, probably Gleevec (imatinib mesylate), which blocks the BCR-ABL cancer gene. Gleevec stops the CML from getting worse, but does not cure it. There are other drugs, such as Sprycel (dasatinib) and Tarigna (nilotinb), which also block the BCR-ABL cancer gene.
Patients who have not had success with Gleevec are usually given Sprycel and Tarigna. All three drugs are taken orally. A bone marrow transplant is the only current way of curing a patient with CML. The younger the patient is the more likely the transplant will be successful.
Patients with Chronic Lymphocytic Leukemia (CLL) may not receive any treatment for a long time after diagnosis. Those who do will normally be given chemotherapy or monoclonal antibody therapy. Some patients with CLL may benefit from allogeneic stem cell transplantation (bone marrow transplant).
All leukemia patients, regardless of what type they have or had, will need to be checked regularly by their doctors after the cancer has gone (in remission). They will undergo exams and blood tests. The doctors will occasionally test their bone marrow. As time passes and the patient continues to remain free of leukemia the doctor may decide to lengthen the intervals between tests.