This cancer, that involves the bone marrow, affects a particular type of white blood cells, lymphoblasts (lymphocytes at an early stage of development). It is the most common leukemia in children, although it affects all age groups.

Like all cancers, acute lymphoblastic leukemia (ALL) is a disease characterized by the malfunctioning of certain cells of the body that multiply uncontrollably, first locally and then in nearby tissues. This form of leukemia is a rare disease that affects children more than adults, and men more frequently than women.¹

The incidence (number of new cases during a given period in a given population) in children is 40 cases per million in European countries (the incidence is essentially the same in all developed countries). The incidence peak is located between 0 and 5 years² in Europe and the United States.

Particularly aggressive, this form of leukemia is a diagnostic and therapeutic emergency. In the past ten years, medical advances and the introduction of new treatments have allowed remarkable progress in cure rates, mainly in children, who withstand chemotherapy better than adults.

Bone marrow, the producer of blood cells

Leukemia affects the bone marrow, the place where blood cells are produced. These cells include erythrocytes (red blood cells responsible for transporting oxygen), leukocytes (white blood cells that defend the body against infection), and thrombocytes (platelets, which aid in clotting).

Acute lymphoblastic leukemia affects stem cells that give rise to a particular type of white blood cells, lymphocytes. Instead of differentiating into mature cells and migrating into the blood, these “blasts” (abnormal cells that have not reached their maturity) proliferate in an unregulated manner. They invade the blood marrow and impede the normal production of blood cells. These blasts may also reach other organs, such as the lymph nodes, liver and spleen.

Risk Factors

ALL, which is neither contagious nor hereditary, has no known cause or triggering factor. In the majority of cases, it occurs in subjects who were previously in good health. However, several risk factors have been identified:

• Exposure to ionizing radiation: accidental, therapeutic (radiation therapy), or occupational
• History of chemotherapy, administered during a prior cancer
• The presence of certain genomic anomalies, including Down syndrom
• Pre-existing blood conditions

To prevent relapses, an outpatient maintenance treatment is administered for two years.

Cancer cells can infiltrate into the meninges, the membranes that surround the brain and spinal cord. This neuro-meningeal involvement is a major cause of relapses in the first year of treatment. For prevention, patients receive cranial radiation therapy and/or a chemotherapy injection.

In the event of relapse, a new chemotherapy is prescribed, starting with a reinduction treatment, again followed by a maintenance and consolidation treatment. A hematopoietic stem cell transplant may also be considered, originating from healthy donors (allograft) or from the patient themselves (autograft).

New therapeutic approaches

While the response rates observed after standard treatments are generally high, some patients will resist or relapse. Research has shown that cancer cells can develop mechanisms for escaping the patient’s immune system, allowing them to not be recognized as dangerous. Cancer cells can thus proliferate in the patient’s body.

New therapeutic approaches are being studied, at different stages of development, to treat these patients. They can use the immune system in order to give it back the ability to eliminate cancer cells. These approaches include targeted therapies, mainly based on the use of specific antibodies for certain tumor cell markers, and immunotherapies.

Key Points

1. Acute lymphoblastic leukemiais a rare disease that especially affects children.
2. Its cause is currently unknownand it does not present specific symptom.
3. During the past few years,the management of this disease has made considerable progress leading to high cure rates, particularly in children.