Leukemia is a term for cancers of the blood cells. It starts in blood-forming tissue such as the bone marrow, which makes the cells that become:
- white blood cells, which fight infection;
- red blood cells, which carry oxygen from the lungs to tissues and organs;
- platelets, which help blood clot to stop bleeding.
In leukemia, the bone marrow makes large numbers of abnormal cells, most often white blood cells. They build up in the marrow and blood and crowd out healthy cells, so the blood can't do its work.
What CML is
Chronic myeloid leukemia (CML) is a chronic leukemia — "chronic" meaning it usually worsens slowly. In CML the bone marrow makes abnormal granulocytes, a type of white blood cell; these abnormal cells are also called blasts. As they crowd out healthy cells, they can lead to infection, anemia and easy bleeding, and they can spread beyond the blood to other parts of the body.
CML usually affects adults during or after middle age. It is rare in children.
The Philadelphia chromosome
Most people with CML have a genetic change called the Philadelphia chromosome, named because researchers in Philadelphia discovered it.
Each cell normally holds 23 pairs of chromosomes, which carry our DNA. In CML, part of the DNA from one chromosome moves to another and joins DNA there, creating a new gene called BCR-ABL. That gene makes the bone marrow produce an abnormal protein that lets leukemia cells grow out of control.
The Philadelphia chromosome is not inherited; it arises during a person's lifetime, for unknown reasons.
Risk factors
It is hard to predict who will get CML, but risk rises with:
- older age;
- being male (CML is slightly more common in men);
- exposure to high-dose radiation.
Symptoms
CML sometimes causes no symptoms. When it does, they can include:
- extreme tiredness;
- unexplained weight loss;
- drenching night sweats;
- fever;
- pain or a feeling of fullness below the ribs on the left side.
Diagnosis
A health care provider may use:
- a physical exam and medical history;
- blood tests — a complete blood count (CBC) with differential, and blood chemistry tests such as a basic or comprehensive metabolic panel, kidney and liver function tests and an electrolyte panel;
- bone marrow tests — aspiration and biopsy, which both remove a sample of marrow and bone for the lab;
- genetic tests for gene and chromosome changes, including the Philadelphia chromosome.
After diagnosis, imaging tests may show whether the cancer has spread.
Three phases
| Phase | Blast cells in blood and marrow | What it means |
|---|---|---|
| Chronic | under 10% | Most people are diagnosed here, many without symptoms; standard treatment usually helps. |
| Accelerated | 10% to 19% | Symptoms are common, and standard treatment may work less well. |
| Blastic | 20% or more | Blasts have spread to other tissues and organs; harder to treat. Tiredness, fever and an enlarged spleen in this phase are called a blast crisis. |
Treatment
- Targeted therapy with tyrosine kinase inhibitors (TKIs), which attack cancer cells while sparing normal ones more than other drugs do. They block tyrosine kinase, the enzyme that drives the marrow to make too many blasts.
- Chemotherapy.
- Immunotherapy.
- High-dose chemotherapy with a stem cell transplant.
- Donor lymphocyte infusion (DLI) after a transplant: healthy lymphocytes — a type of white blood cell — from the stem cell donor are infused into the bloodstream, where they may kill remaining cancer cells.
- Splenectomy, surgery to remove the spleen.
The choice depends on the phase, age, overall health and other factors. When signs and symptoms shrink or disappear, CML is in remission, but it can return and need more treatment.
Sources
- MedlinePlus, National Library of Medicine: "Chronic Myeloid Leukemia," with information from the National Cancer Institute, National Institutes of Health.
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