Chronic myelogenous leukemia
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Chronic myelogenous leukemia (CML) is rare form of cancer that occurs in the bone marrow. Bone marrow is a tissue that has texture of a sponge located inside the bones where blood cells are produced. The development of CML results in an increased number of white blood cells in the blood.
CML is a type of disease that develops gradually. The disease impacts on elders and rarely occurs in children. The advancement of treatments has a high chance for patients with chronic myelogenous leukemia to recover. Majority of the patients have more prospective for remission and prolonged life after being diagnosed.
Chronic myelogenous leukemia is also known as chronic myeloid leukemia and chronic granulocytic leukemia.
Symptoms
Chronic myelogenous leukemia is usually asymptomatic. The disease could be found during a blood test. Once it has been detected, the following symptoms may occur:
- Fever
- Bone pain
- Bruising or easy bleeding
- Appetite loss
- Feeling tired
- Unintentional weight loss
- Pain or fullness below the ribs on the left side
- Night sweats
Causes
Chronic myelogenous leukemia develops when there is a malfunction of genes of bone marrow cells.
- An abnormal chromosome develops. Normal human cells have 23 pairs of chromosomes. These chromosomes have DNA that consists of genes which control the cells in the body. When chronic myelogenous leukemia occurs, the chromosomes switch their sections with each other. When one section of chromosome 9 swaps its place with a section of chromosome 22, an extra-short chromosome 22 (Philadelphia chromosome) and extra-long chromosome 9 are produced. The extra-short chromosome 22 exists in the blood cells of 90% of patients with chronic myelogenous leukemia.
- Chromosome abnormality creates a new gene. The swapping of DNA between the chromosomes creates an oncogene named BCR-ABL. The BCR-ABL gene contains instructions telling the abnormal blood cell to produce too much of tyrosine kinase, which is the protein promotes certain blood cells to grow out of control.
- New gene allows too many diseased blood cells. Blood cells arise in a sponge-like material contained inside the bones, called bone marrow. When bone marrow is functioning in a normal way, immature cells or blood stem cells are created within a control. These immature cells are then mature and transform into numerous types of blood cells throughout the body known as, red blood cells, white blood cells and platelets.
When chronic myelogenous leukemia occurs the BCR-ABL gene results in the tyrosine kinase that enables the growth of excessive number of white blood cells. The abnormal Philadelphia chromosome exists in almost of the cells. Unlike normal cells, white blood cells that are diseased are not produced and die. They accumulate by in mass and decrease the growth of healthy blood cells, destroying the bone marrow.
Risk factors
- Advanced age
- Gender: Male
- Exposure to radiation from radiation therapy
Having a family history of chronic myelogenous leukemia is not considered as a risk factor. The mutations that results in the development of the disease are not passed genetically. The mutation occurs after the child has born.
Diagnosis
- Physical examination: Vital signs such as pulse and blood pressure will be checked. Lymph nodes, spleen and abdomen need to be examined to see if they have grown from normal size.
- Blood tests:
- Complete blood count. To see the abnormalities present in blood cells, such as extensive amount of white blood cells.
- Blood chemistry tests. To evaluate the functions of the organs, which could show the abnormalities and help making the diagnosis.
- Bone marrow biopsy and bone marrow aspiration: To gather bone marrow samples from the hipbone and send for laboratory tests.
- Tests to find out the Philadelphia chromosome: Fluorescence in situ hybridization (FISH) analysis and the polymerase chain reaction (PCR) test are specialized procedures that analyze blood or bone marrow samples to find the Philadelphia chromosome or the BCR-ABL gene.
Chronic myelogenous leukemia is classified into phases according to the severity of the disease. The phase is evaluated by the proportion of diseased cells to the healthy cells in the blood or bone marrow. If the number of diseased cells is high, it indicates that chronic myelogenous leukemia is at an advanced phase.
The phases of chronic myelogenous leukemia include:
- Chronic is the initial stage and commonly results in the best response to treatment.
- Accelerated is the transitional phase from minor to more severe.
- Blast is a severe stage that leads life-threatening condition.
Treatment
Chronic myelogenous leukemia treatment aims to remove blood cells that consist of abnormal BCR-ABL gene, which causes excess number of diseased blood cells. For primary cases, treatment starts with targeted drugs.
Targeted drug therapy
Targeted drugs work by attacking certain aspects of cancer cells that grow and multiply.
Its goal is to achieve a long-term remission of the disease. For chronic myelogenous leukemia, the protein produced by the BCR-ABL gene – tyrosine kinase are targeted.
Targeted drugs that hinder the action of tyrosine kinase are Imatinib (Gleevec), Dasatinib (Sprycel), Nilotinib (Tasigna), Bosutinib (Bosulif) and Ponatinib (Iclusig).
Patients who have been diagnosed with chronic myelogenous leukemia are treated by targeted therapy drugs at the first stage. Side effects include, skin swelling or puffiness, nausea, muscle cramps, fatigue, diarrhea and skin rashes.
To evaluate the effectiveness of targeted therapy, blood tests are carried out to find the presence of the BCR-ABL gene. If chronic myelogenous leukemia does not respond well to targeted therapy or becomes resistant to it, alternative targeted drugs will be considered.
Bone marrow transplant (stem cell transplant)
Bone marrow transplant is the only treatment option that can be used as a definite cure for chronic myelogenous leukemia. Although this treatment tend to be reserved for patients who did not have good response to other treatments, because bone marrow transplants hold a high risk and chance for complications to arise. The procedure is done by giving extensive doses of chemotherapy, which are aimed to kill blood-forming cells in the bone marrow. Blood stem cells that have taken from a donor are then infused with in the bloodstream. The new cells produce new healthy blood cells and replace the cells that are diseased.
Chemotherapy
Chemotherapy is a drug that is designed to kill rapidly growing cancer cells, including leukemia cells. The drug is often given with the combination of targeted therapy to treat advanced stage of chronic myelogenous leukemia.
