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Chronic Myeloid Leukemia (CML)

Chronic Myeloid Leukemia (CML) is a rare form of blood cancer in children. Due to a chromosome abnormality that occurs in the blood cells, the Philadelphia chromosome, there is an uncontrolled growth of the white blood cells in particular. As a result, the other blood cells cannot be properly produced, and the abnormal cells can also accumulate outside the bone marrow.

Symptoms of this disease

Typical symptoms of CML are fatigue, listlessness, pain in the bones or a swollen stomach because of a large spleen. But this is often diagnosed by chance. The severity of the symptoms is also determined by the phase in which the disease is.

How do we make the diagnosis?

The disease can be diagnosed with blood and bone marrow tests. The level of the white blood cells in the blood is elevated. When using cytogenetic diagnostics, an abnormal chromosome is almost always found in the white blood cells, the Philadelphia chromosome. In the blood and bone marrow, with molecular diagnostics, the protein can also show what is made by that abnormal chromosome; the BCR-ABL protein. This protein is the driving force behind the uncontrolled growth of the white blood cells

The course of (untreated) CML consists of 3 phases; the chronic phase, the accelerated phase and the blast phase. This classification depends on the blood levels.
An ultrasound of the abdomen is often also made to determine the size of the spleen.

Treatment of Chronic Myeloid Leukemia

Chronic Myeloid Leukemia (CML) is treated with drugs that act on the BCR-ABL protein and thus block the "growth signal". These drugs, tyrosine kinase inhibitors, have to be swallowed long-term on a daily basis and usually do not have too many serious side effects. The effect of the treatment is measured in the blood (and bone marrow) by determining the decrease of the BCR-ABL protein. Sometimes an insensitivity to the tyrosine kinase inhibitor can occur. In such cases, another tyrosine kinase inhibitor is given. In some of the adults with a long-term good response, it is possible to stop the tyrosine kinase inhibitor. Stopping the tyrosine kinase inhibitor if the BCR-ABL protein is no longer present long-term is now being tried with children too. 

If there is a very high white blood cell count at diagnosis, or if the patient presents in the blast phase, chemotherapy is given in addition to the tyrosine kinase inhibitor. If too many side effects occur, or if there is also insensitivity to different tyrosine kinase inhibitors, then sometimes a stem cell transplant is done. This is usually also necessary for patients with a blast crisis. The abnormal stem cells – from which the white blood cells are formed – are replaced with those of a healthy donor.