La leukemia is cancer of the tissues responsible for forming blood, which are immature blood cells found in the bone marrow (= soft, spongy material located in the center of most bones).

The disease usually starts with an abnormality in the formation of blood cells in the bone marrow. Abnormal cells (or leukemia cells) multiply and outnumber normal cells, preventing their proper functioning.

Types of leukemia

There are several types of leukemia. They can be classified according to the speed of progression of the disease (acute or chronic) and according to the stem cells from the bone marrow from which they develop (myeloid or lymphoblastic). Leukemia usually refers to cancers of the white blood cells (lymphocytes and granulocytes, the cells responsible for immunity), although some very rare cancers can affect red blood cells and platelets.

Acute leukemia:

The abnormal blood cells are immature (= blasts). They do not perform their normal function and multiply rapidly so the disease progresses quickly too. Treatment should be aggressive and applied as early as possible.

Chronic leukemia:

The cells involved are more mature. They multiply more slowly and remain functional for some time. Some forms of leukemia can go unnoticed for several years.

Myeloid leukemia

It affects granulocytes and blood stem cells found in the bone marrow. They make abnormal white blood cells (myeloblasts). There are two types of myeloid leukemia :

• Acute myeloid leukemia (AML)

This form of leukemia starts suddenly, often over a few days or weeks.

AML is the most common form of acute leukemia in adolescents and young adults.

AML can start at any age, but is more likely to develop in adults 60 years of age and older.

• Chronic myelogenous leukemia (CML)

La chronic myelogenous leukemia is also called chronic myelocytic leukemia ou chronic granular leukemia. This type of leukemia develops slowly, over months or even years. Symptoms of the disease appear as the amount of leukemia cells in the blood or bone marrow increases.

It is the most common form of chronic leukemia in adults between the ages of 25 and 60. Sometimes it does not require treatment for several years.

Lymphoblastic leukemia

Lymphoblastic leukemia affects lymphocytes and produces lymphoblasts. There are two types of lymphoblastic leukemia:

• Acute lymphoblastic leukemia (ALL)

This form of leukemia starts suddenly and progresses rapidly over a few days or weeks.

Also called acute lymphocytic leukemia ou acute lymphoid leukemia, it is the most common form of leukemia in young children. There are several subtypes of this form of leukemia.

• Chronic lymphoblastic leukemia (CLL)

This form of leukemia most often affects adults, especially between the ages of 60 and 70. People with the condition may have no or very few symptoms for years and then have a phase in which leukemia cells grow rapidly.

Causes of leukemia

The causes of leukemia are still poorly understood. Scientists agree that the disease is a combination of genetic and environmental factors.

Prevalence

In Canada, one in 53 men and one in 72 women will develop leukemia in their lifetime. In 2013, it is estimated that 5800 Canadians will be affected. (Canadian Cancer Society)

In France, leukemia affects around 20 people each year. Leukemia accounts for about 000% of childhood cancers, 29% of which are acute lymphoblastic leukemias (ALL).

Diagnosis of leukemia

Blood test. Testing a blood sample can detect whether the levels of white blood cells or platelets are abnormal, suggesting leukemia.

Bone marrow biopsy. A sample of bone marrow removed from the hip can detect certain characteristics of the leukemia cells which can then be used to suggest options for the treatment of the disease.