Chronic myeloid leukemia is a type of blood cancer that originates in the blood-forming cells of the bone marrow and subsequently transmits to the blood. It is characterized by a gradual progression, with signs and treatment alternatives varying depending on the stage of the disease.
CML is sometimes referred to by other names, like chronic granulocytic leukemia, chronic myelogenous leukemia, or chronic myelocytic leukemia. As stated by the American Cancer Society, CML represents approximately 15 percent of adult leukemia cases but is rare in children. Additionally, the Leukemia & Lymphoma Society identifies CML as one of the 4 common kinds of leukemia.
The progression of CML is categorized into three distinct phases:
- Chronic Phase: This is the initial stage where the disease is often diagnosed. At this point, CML usually responds to treatment, and many individuals may not exhibit symptoms. The disease may be detected through routine blood examinations performed for other health concerns.
- Accelerated Phase: If the chronic phase remains unmedicated, the disease can advance to the accelerated phase. During this stage, the cancer progresses more rapidly, and individuals may begin to experience symptoms like extreme tiredness and weight loss.
- Blast Phase: This phase is akin to acute myeloid leukemia and is marked by a range of severe signs. The cancer may extend beyond the blood and bone marrow, leading to more significant health issues.
Symptoms
The symptoms of chronic myeloid leukemia can vary depending on the stage of the disease. Throughout the chronic phase, it is common for individuals to not experience any indications at all. When symptoms do arise, they are often nonspecific, they can overlap with those of several other conditions. This makes it challenging for individuals to associate these symptoms directly with CML.
Common symptoms of CML, when they do take place, may include weakness, night sweats, fever, a feeling of fullness after eating only a small amount, extreme tiredness, weight loss, bone pain, abdominal discomfort or fullness, and an enlarged spleen. The Leukemia & Lymphoma Society notes that many of these symptoms may be related to anemia or other issues associated with CML.
Causes
As stated by the American Cancer Society, most episodes of chronic myeloid leukemia are caused by alterations or mutations in the DNA. Specifically, CML often involves a translocation, where parts of chromosomes 9 and 22 exchange segments of their genetic material. This process results in chromosome 22 becoming shorter than normal.
The shortened chromosome 22 is known as the Philadelphia chromosome, which is present in almost all people affected by the CML. The translocation of these chromosomes gives way to the formation of a new, malignant gene called BCR-ABL. This gene produces the BCR-ABL protein, which drives the rapid growth and division of cells of CML.
Risk Factors
Several risk factors can increase the likelihood of developing chronic myeloid leukemia. According to the American Cancer Society, age is a significant factor, with the risk of CML rising as a person gets older. Additionally, exposure to high levels of radiation, like an atomic bomb blast or a nuclear reactor accident is known to increase the chance of developing this type of leukemia. Furthermore, CML is more common in men than in women, indicating that sex is also a contributing risk factor.
Diagnosis
In the early stages of CML, the disease often does not produce noticeable symptoms. As a result, CML may be detected during a blood examination if an abnormal count of white blood cells is found.
When symptoms do appear, they are typically nonspecific, making it necessary for healthcare providers to perform additional tests to confirm the diagnosis and exclude other potential causes. To diagnose CML, several tests may be ordered:
- Complete Blood Count with Differential: It assesses the different kinds of cells of white blood present, and also provides information on red blood cells and platelets.
- Biopsy and Bone Marrow Aspiration: This procedure allows healthcare providers to test abnormalities in the cells of bone marrow.
- Peripheral Blood Smear: It helps determine the number, shapes, and sizes of various blood cells.
- Fluorescence In Situ Hybridization: This technique studies chromosomes and genes within the cells.
- Cytogenetic Analysis: It detects abnormalities of chromosomes in the bone marrow.
- Quantitative Polymerase Chain Reaction: qPCR checks the quantity of the BCR-ABL1 gene present in the bone marrow or blood.
These diagnostic tests are essential for accurately identifying CML and guiding appropriate treatment strategies.
Treatment
There are several treatment alternatives available for chronic myeloid leukemia, and ongoing research continues to explore new and improved methods for managing the disease. The National Cancer Institute detects a range of present treatments for CML, including targeted therapy, chemotherapy, high-dose chemotherapy combined with stem cell transplant, donor lymphocyte infusion, surgery, and immunotherapy.
The choice of treatment depends on various factors, like the level of CML, the patient’s age, and complete health. An intervention team will collaborate with the patient to develop a personalized treatment plan.
Treatment for the Chronic Phase
For individuals diagnosed during the chronic phase, healthcare providers typically recommend treatments like splenectomy, chemotherapy, targeted therapy utilizing tyrosine kinase inhibitors, or participation in clinical trials offering new treatments.
Treatment for the Accelerated Phase
In the accelerated phase, common treatment options include targeted therapy with tyrosine kinase inhibitors, donor stem cell transplant, high-dose chemotherapy, or a combination of tyrosine kinase inhibitor therapy followed by donor stem cell transplant. Other options include immunotherapy without or with chemotherapy, and participation in clinical trials testing new treatments.
Treatment for the Blastic Phase
The blastic phase of CML is more aggressive and may require intensive treatment. Options include high-dose chemotherapy, targeted therapy with tyrosine kinase inhibitors like imatinib mesylate, dasatinib, or nilotinib, donor stem cell transplant, and chemotherapy to enhance the standard of life and alleviate signs. Clinical trial participation may also be considered.
Each phase of CML requires a tailored approach to treatment, with the goal of managing the disease effectively and improving the patient’s quality of life.
Outlook
In common, the earlier an individual begins treatment for chronic myeloid leukemia the better their prognosis. However, factors such as age, complete health, and the phase of CML at diagnosis also influence the outcome.
A significant published study in 2012 provides survival statistics for CML since the introduction of these drugs. For individuals in the chronic phase, the survival rate is approximately 87 percent after eight years. In the accelerated phase, the survival rate is around 75 percent after eight years. For those in the blastic phase, the median survival period is about six months. These figures reflect the progress made in CML treatment and the importance of early intervention.
Summary
Chronic myeloid leukemia is a kind of blood cancer that begins in the bone marrow and can spread to the blood. Symptoms may be nonspecific, and diagnosis often involves tests like a complete blood count and cytogenetic analysis. Risk factors include age, radiation exposure, and sex. Treatments vary by disease phase and include targeted therapy, chemotherapy, and stem cell transplants. Early treatment generally enhances outcomes, though survival data with newer medications is still emerging. Recent statistics show an 87 percent survival rate for the chronic phase, 75 percent for the accelerated phase, and a median survival of six months for the blastic phase.
