Chronic leukaemia - characteristics and treatment
Chronic myeloid leukaemia (CML) is a clonal myeloproliferative disorder originating from a pluripotent haematopoietic stem cell. CML may also be called chronic granulocytic leukaemia or chronic myelogenous leukaemia. It accounts for 7–20 per cent of all adult leukaemias, with an incidence of one to two per 100,000.
The median age of onset is 40–60 years, but the disease can occur at any age. It is slightly more common in males, but the course of the disease is similar for either sex (male:female ratio is 2.2:1.2). The cause of CML is unknown.1,2
Pathology of CML
In 90–95 per cent of patients there is a translocation of genetic material between the long arms of chromosome 22 and chromosome.9 This forms the Philadelphia (Ph) chromosome containing the oncogene bcr-abl. The protein encoded by bcr-abl has an increased tyrosine kinase activity that alters multiple signal transduction pathways, leading to malignant transformation of haematopoietic cells in the myeloid lineage and consequent myeloid expansion in the bone marrow. The malignant cells have a longer lifespan and more rapid proliferation than normal blood cells.1–5
The presence of the bcr-abl transcript on the Ph chromosome is diagnostic of CML. In Ph-negative patients, the presence of bcr-abl from another genetic abnormality is confirmed by cytogenetics.
There are three classic phases of CML; chronic, accelerated and blast (terminal) phase. Disease progression, thought to be caused by further genomic instability, usually follows this pattern, but up to 40 per cent of patients transform from the chronic to blast phase directly. The duration of the chronic phase varies from three months to 22 years, with a median of five years. The majority of patients will transform to the blast phase and die of their disease.1,2,4–9
Diagnosis and symptoms
The symptoms presented at diagnosis are generally those seen in the chronic phase and represent disorders of the myeloid lineage (see Panel 1 and Table 1, p111). Diagnosis can be incidental following a routine blood test in a patient who is asymptomatic.1,2,4,7,8
Aims of treatment
There are several treatment options available but, currently, the only potentially curative option is an allogenic bone marrow transplant (BMT). All other treatments aim to induce a haematological remission or response, thereby controlling the symptoms, and a cytogenetic response delaying disease progression. In the accelerated and blast phases, the aim is to restore the patient to the chronic phase.
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Citation: Hospital Pharmacist URI: 10976727
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