The leukemia is a cancer of tissues responsible for the formation of blood, that is to say of immature blood cells in the bone marrow (= soft, spongy material in the center of most bones).
The disease usually begins with an abnormality in the formation of blood cells in the bone marrow. Abnormal cells (or leukemic cells ) multiply and become more numerous than normal cells, thus preventing their proper functioning.
Types of leukemia
There are several types of leukemia. They can be classified according to the speed of the disease (acute or chronic) and according to the stem cells of 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.
Abnormal blood cells are immature (= blasts). They do not perform their normal function and multiply rapidly so that the disease also evolves rapidly. Treatment should be aggressive and applied as soon as possible.
The cells involved are more mature. They multiply more slowly and remain functional for a while. Some forms of leukemia may go unnoticed for several years.
It affects the granulocytes and blood stem cells present in the bone marrow. They produce abnormal white blood cells (myeloblasts). There are two types of myeloid leukemia :
- Acute myeloid leukemia (AML)
This form of leukemia begins suddenly, often in a few days or weeks.
AML is the most prevalent form of acute leukemia in adolescents and young adults.
AML can occur at any age but is more likely to develop in adults 60 years of age and older.
- Chronic myeloid leukemia (CML)
The chronic myelogenous leukemia is also called myelocytic leukemia chronic or chronic leukemia grainy . This type of leukemia develops slowly, over months or even years. Symptoms of the disease manifest as the amount of leukemic cells in the blood or bone marrow increases.
It is the most common form of chronic leukemia in adults between 25 and 60 years of age. It does not require treatment for several years.
Lymphoblastic leukemia affects lymphocytes and produces lymphoblasts. There are two types of lymphoblastic leukemia:
- Acute lymphoblastic leukemia (LLA)
This form of leukemia begins suddenly and evolves rapidly in a few days or weeks.
Also called acute lymphocytic leukemia or acute lymphocytic 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 60 and 70 years of age. Individuals may have no or very few symptoms for years, and then present a phase in which the leukemic cells grow rapidly.
The causes of leukemia
The causes of leukemia are still poorly understood. Scientists agree that the disease is a combination of genetic and environmental factors.
In Canada, one in 53 men and one in 72 women will have leukemia in their lifetime. In 2013, an estimated 5,800 Canadians will be reached. (Canadian Cancer Society)
In France, leukemia affects approximately 20,000 people each year. Leukemia accounts for about 29% of cancers in children, 80% of which are acute lymphoblastic leukemia (ALA).
Diagnosis of leukemia
Blood test. The analysis of a blood sample makes it possible to detect whether the levels of white blood cells or platelets are abnormal, suggesting leukemia.
Biopsy of the bone marrow. A sample of bone marrow removed from the hip allows the detection of certain characteristics of the leukemic cells which then propose options for the treatment of the disease.