Leukemia in Children and Young Adults

Children and teens rarely get cancer. Of those who do, the most common type of cancer in children is leukemia. Leukemias account for 28 percent of all cancers in children.¹

There are different types of leukemia. The two that most often occur in children are acute lymphocytic leukemia (ALL) and acute myeloid leukemia (AML). Both ALL and AML are fast-growing cancers that require treatment to stop from growing. These types of leukemia generally respond well to treatment.¹

What is leukemia?

Leukemia is a cancer in which the white blood cells (WBCs) abnormally multiply in the bone marrow and blood. The large number of irregular WBCs do not fight infection properly, and they can disrupt the formation of red blood cells and platelets.²

Leukemias are named for the type of white blood cell that they develop from. Lymphocytic leukemias develop from the immature lymphoid cells, which can become B cells, T cells, and natural killer cells. Myeloid leukemias (also called myelogenous leukemias or myelocytic leukemias) develop from immature myeloid cells, which can become white blood cells, red blood cells, and platelets.^1-4

Leukemias are also classified as acute or chronic. Acute leukemias are fast-growing and can progress quickly if not treated, however, they generally respond well to treatment. Chronic leukemias are slower growing, but they can sometimes be harder to treat. Almost all leukemias that occur in children are acute. Rarely, a child can develop a chronic leukemia.²

What is acute lymphocytic leukemia (ALL)?

Approximately 3 out of 4 childhood leukemias are classified as ALL. The risk of ALL is greatest in children younger than 5 years of age and is most often diagnosed between ages 2 and 5. ALL is more common in Hispanic and white children than in African American and Asian American children. It is more common in boys than in girls.³

ALL develops from the lymphoid cells, which normally become B cells, T cells, and natural killer cells. ALL can be divided into subtypes including B cell leukemia and T cell leukemia. It is also known as acute lymphoblastic leukemia or acute lymphoid leukemia. Several ALL subtypes exist.⁴

What is acute myeloid leukemia (AML)?

Most of the remaining cases of childhood leukemia are AML. AML can develop in children of any age, but it is most common during the first 2 years of life or during the teen years. It occurs equally in girls and boys.³

AML develops from myeloid cells, which normally develop into white blood cells, red blood cells, and platelets. Several subtypes of AML exist.⁵

How is leukemia staged in children?

Childhood AML does not have a standard staging system and is generally classified by its subtype, which can help to guide treatment recommendations. Childhood ALL is also usually classified by its subtype. B cell ALL and T cell ALL are the two main subtypes, named for the type of white blood cell they develop from.^6,7

What is the prognosis for childhood leukemia?

The prognosis, or expected outcome, depends on many factors, including:

• How quickly the cancer responds to treatment - Those whose leukemia responds relatively quickly generally have a better outcome.
• The age of the child - In ALL, children between the ages of 1 and 9 with B-cell ALL tend to have a higher rate of cure. In AML, children younger than age 2 may have a better outcome than older children. However, age tends to not be a major factor in the prognosis of childhood AML.
• The number of white blood cells at diagnosis - For ALL, children who have a count of more than 50,000 cells per cubic millimeter at diagnosis may need increasingly intense treatment. For AML, a count of less than 100,000 cells per cubic millimeter at diagnosis tend to be cured more frequently than patients with higher white blood cell counts at diagnosis.
• Subtype - There are differences between the subtypes of ALL and AML, with some subtypes having more favorable outlooks than others.
• Ethnicity - Children of African American or Hispanic backgrounds tend to have a lower cure rate than children from other ethnicities.
• Gender – Girls with ALL tend to be cured a slightly better rates than boys.⁸

Overall, the survival rate for childhood leukemia has steadily increased over the last few decades. Survival rates are based on past data of people who survive a set amount of time after diagnosis. In cancer estimates, experts use the "5-year survival rate" as a marker. However, it is important to keep in mind that many people live beyond 5 years after diagnosis and the statistics are not necessarily predictive for any one individual.

The 5-year survival rate for ALL in children is 91 percent, and the 5-year survival rate for AML in children is 66 percent, but will vary by subtype of AML.⁹