What is Chronic Myelogenous Leukemia (CML)?

Leukaemia is cancer of the white blood cells. There are essentially two broad categories of leukemia – acute and chronic.

Chronic leukaemia means the condition progresses slowly over years as opposed to a more aggressively progressing acute leukemia.

Leukemia types

Leukemia is further divided according to the type of white blood cells it affects. There are two main types:-

• If the myeloid cells are cancerous it is termed chronic myeloid leukemia (CML). Myeloid cells are those white blood cells that fight bacteria and parasitic infections and also prevent the spread of tissue damage
• If the lymphoid cells are affected, it is termed chronic lymphoid leukemia (CLL). The lymphoid cells are those white blood cells that help fight viral infections and some bacterial infections

Symptoms of CML

One of the earliest symptoms of CML includes fatigue, weight loss, loss of appetite, night sweats, anemia, bone pain and easy bruising and bleeding tendencies. There is also an increased susceptibility to infections. 

Pathology of CML

A normal cell is tightly regulated by its DNA in terms of when it grows, matures, reproduces of divides and when it dies. Some defects in the DNA regulating the cells may turn them rogue and these cells begin to multiply and grow uncontrollably and do not undergo programmed cell death that occurs normally under a genetic regulation. This leads to formation of a tumour or a cancer.

In leukemia the blood cells are affected similarly. In CML the myeloid cells that are normally produced by bone marrow turn cancerous.

Bone marrow is a spongy material found inside the bones. It produces stem cells that have the ability to create other specialised cells that carry out important functions. The stem cells in bone marrow produce three important types of blood cells including red blood cells, white blood cells and platelets.

In CML the stem cells are affected and they begin to produce more white blood cells than are needed. This disrupts the normal balance of cells in the blood. There is a lack of red blood cells, leading to anemia, and platelets, leading to bleeding tendencies and easy bruising.

CML epidemiology

CML is a relatively uncommon type of cancer. In the United Kingdom around 600 persons are diagnosed with CML annually. The disease commonly affects persons between ages of 40 and 60 years.

Treatment of CML

CML, like most other leukemias, is treated mainly by chemotherapy. There are some specific agents called tyrosine kinase inhibitors that can be used in some genetic subtypes of CML. Bone marrow and stem cell transplant are one of the important modalities of treating these patients as well.

Prognosis of CML

The prognosis or outcome of CML patients depends on several factors. One of the important features, however, is how a person responds to medication. Around 60 to 65% patients respond to tyrosine kinase inhibitors like Imatinib.