Even though leukemia in children is rare and less common than in adults, it accounts for 30% of pediatric cancers. In Belgium, it is estimated that ninety children develop leukemia every year.
Leukemia is a cancer of the blood. Blasts (abnormal cells) develop from white cell precursors. Depending on the characteristics of these cells, leukemia is classified as either lymphoblastic leukemia or myeloblastic leukemia.
The majority of leukemias in children are acute leukemias. Acute Lymphoblastic Leukemia (ALL) and Acute Myeloid Leukemia (AML) account for 80% and 20% of acute childhood leukemias respectively. It is very important not to compare the leukemias and leukemia treatments of children and adults. The overall survival rate today in Belgium is 90% for Acute Lymphoblastic Leukemia and 60% for Acute Myeloid Leukemia.
What is bone marrow?
Leukemia starts in the bone marrow, the tissue found inside our bones.
Bone marrow ensures the production of blood cells.
Like a factory, the bone marrow produces:
- red blood cells that carry oxygen to the various organs
- white blood cells that help protect the body against disease
- platelets which help the blood to clot (to minimize bleeding when injured for example).
In the case of leukemia, the bone marrow produces immature or abnormal cells called blasts. These blasts invade the bone marrow and take over the entire “production chain” preventing it from working as it should.
The decrease in the various cell lines has several consequences. The child feels tired, becomes breathless easily and looks pale due to the decrease in red blood cells. They often have frequent infections and fever due to the decrease in white blood cells. In addition, the decrease in platelets results in bruising, petechiae (tiny red spots on the skin), bleeding, etc.
The blasts can also invade other organs such as the lymph nodes, spleen, liver, testicles, ovaries, the skin or the cerebrospinal fluid (the fluid surrounding the brain). This invasion tends to result in large palpable masses.
The diagnosis of leukemia is made based on the results of a blood test together with the analysis of a bone marrow aspiration which looks at the bone marrow under a microscope.
An ultrasound of the abdomen, chest X-ray, bone marrow aspiration and sometimes other tests are used to determine how far the disease has spread. In addition to the child’s symptoms and medical history, the doctors examine several characteristics of the blastic cells:
- the number of blasts in the blood at the time of diagnosis,
- markers found on the surface of the blasts (membrane markers) to determine their origin and maturation,
- any chromosomal or genetic abnormalities of the blastic cells
The type of disease is defined based on these different criteria. The different types of leukemia are very different in terms of prognosis, evolution and management.
As soon as the diagnosis of leukemia is made, treatment is started rapidly and initially includes chemotherapy.
Depending on certain criteria of the disease, other therapeutic arms may be used such as radiotherapy or a stem cell transplant.
Every patient has a treatment protocol that is adapted according to their disease, tolerance and response to the different treatments.