--- title: Chronic Myeloid Leukemia (CML) url: "https://www.yyhmedical.com/en/guide/blood/chronic-myeloid-leukemia" type: MedicalWebPage inLanguage: en-US --- # Chronic Myeloid Leukemia (CML) > Chronic myeloid leukemia (CML) is a cancer of the blood and bone marrow characterized by the BCR::ABL1 fusion gene. With tyrosine kinase inhibitor (TKI) therapy, many people with CML can achieve long-term disease control. ## Overview Chronic myeloid leukemia (CML) is a cancer of the blood and bone marrow in which abnormal myeloid cells grow and multiply excessively. CML can occur at any age but is most common in adults and is rare in children. Compared with acute leukemia, CML usually progresses more slowly. The disease is generally classified into **chronic phase, accelerated phase, and blast phase**, with most people diagnosed during the chronic phase. A defining feature of CML is the **Philadelphia chromosome (Ph chromosome) and the BCR::ABL1 fusion gene**. This genetic change is important for both diagnosing CML and selecting targeted treatment. ## Causes The exact cause of CML is not known, but the key molecular changes that drive the disease are well understood. Human cells normally contain 23 pairs of chromosomes. In the leukemia cells of most people with CML, genetic material is exchanged between chromosomes 9 and 22. This change is known as the **t(9;22) chromosomal translocation**. The translocation creates an abnormal chromosome 22 called the **Philadelphia chromosome** and forms the **BCR::ABL1 fusion gene**. The BCR::ABL1 fusion gene produces an abnormal tyrosine kinase that remains continuously active. This sends ongoing growth signals to myeloid cells, allowing them to multiply and survive when they normally would not. Over time, these abnormal cells build up in the blood and bone marrow and interfere with normal blood cell production. For most people, it is not known what causes this chromosomal change. CML is generally not an inherited disease passed from parent to child. ## Signs and Symptoms Some people with CML have no symptoms when they are diagnosed, and the disease may be found during a routine physical exam or blood test. When symptoms occur, they may include: - Ongoing fatigue or weakness - Fever - Unexplained weight loss - Loss of appetite - Night sweats - Pale skin - Easy bleeding or bruising - Pain, pressure, or fullness under the ribs on the left side - Feeling full after eating only a small amount Fullness or discomfort in the upper left abdomen may be related to an **enlarged spleen**. ## Diagnosis If blood test results or symptoms suggest CML, additional tests may be performed to confirm the diagnosis and better understand the disease. ### **Blood Tests** A complete blood count (CBC) measures the number of different types of blood cells. People with CML often have a high white blood cell count and may also have abnormalities in other blood cell counts. ### **Bone Marrow Tests** Bone marrow aspiration and biopsy may be used to examine the number, appearance, and other characteristics of cells in the bone marrow and provide additional information for diagnosis and disease assessment. ### **Philadelphia Chromosome and BCR::ABL1 Testing** Tests such as chromosome analysis, fluorescence in situ hybridization (FISH), and polymerase chain reaction (PCR) can be used to detect the Philadelphia chromosome or the BCR::ABL1 fusion gene. BCR::ABL1 testing is important not only for diagnosing CML but also for monitoring treatment response over time. ## Treatment The main goals of CML treatment are to suppress BCR::ABL1-positive leukemia cells, achieve long-term disease control, and reduce the risk of disease progression. The development of tyrosine kinase inhibitors (TKIs) has transformed CML treatment. For most people with chronic-phase CML, a TKI is the main treatment. ### **Tyrosine Kinase Inhibitors (TKIs)** TKIs work by blocking the abnormal tyrosine kinase produced by the BCR::ABL1 fusion gene, interrupting signals that help CML cells grow and survive. Several TKIs are available for CML, including **imatinib, dasatinib, nilotinib, bosutinib, ponatinib, and asciminib**. The choice of TKI depends on several factors, including the phase of CML, BCR::ABL1 mutation status, response to previous treatment, age, other health conditions, and the potential side effects of each medication. If treatment is not working as expected, resistance develops, or side effects become difficult to manage, the treatment plan may be adjusted. ### **Treatment Monitoring** During TKI treatment, **BCR::ABL1 levels are monitored regularly** to evaluate how well the leukemia is responding to treatment. Changes in BCR::ABL1 levels over time help assess treatment response and guide decisions about whether to continue or adjust therapy. ### **Treatment-Free Remission (TFR)** Some people who have maintained a deep molecular response for a sustained period may be able to try stopping TKI therapy under close medical supervision. This is known as **treatment-free remission (TFR)**. TFR is not appropriate for everyone. People who stop treatment need frequent BCR::ABL1 monitoring, particularly during the early period after stopping therapy. If molecular relapse occurs, TKI treatment usually needs to be restarted. TKI therapy should not be stopped without discussing it with the treating healthcare team. ### **Hematopoietic Stem Cell Transplantation (HSCT)** With the effectiveness of TKI therapy, hematopoietic stem cell transplantation is no longer the first treatment for most people with chronic-phase CML. An **allogeneic hematopoietic stem cell transplant (allo-HSCT)** may be considered for selected patients whose CML does not respond adequately to TKIs, develops certain forms of drug resistance, or progresses to accelerated or blast phase. Allogeneic HSCT offers the possibility of a cure but also carries significant risks, including graft-versus-host disease (GVHD) and serious infections. The decision depends on the disease status, response to previous treatments, age, overall health, and donor availability. ### **Chemotherapy** With the widespread use of TKIs, traditional chemotherapy now has a limited role in chronic-phase CML. In some situations, particularly when CML progresses to blast phase, chemotherapy may be combined with a TKI or other treatments. ###  **Clinical Trials** Clinical trials study new treatments, treatment combinations, and new ways of using existing therapies for CML. For people who are not responding adequately to treatment, develop resistance, or need additional treatment options, discussing available clinical trials with the healthcare team may be helpful. ## Content attribution (YMYL) - Author: - Medically reviewed by: - Last reviewed: - First published: - Sources: - National Cancer Institute (NCI). Chronic Myelogenous Leukemia Treatment (PDQ®)–Patient Version. (https://www.cancer.gov/types/leukemia/patient/cml-treatment-pdq) - National Cancer Institute (NCI). Chronic Myelogenous Leukemia Treatment (PDQ®)–Health Professional Version. (https://www.cancer.gov/types/leukemia/hp/cml-treatment-pdq) - American Cancer Society (ACS). Chronic Myeloid Leukemia (CML). (https://www.cancer.org/cancer/types/chronic-myeloid-leukemia.html) - Leukemia & Lymphoma Society (LLS). Chronic Myeloid Leukemia (CML). 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