Childhood Leukemia: Types and Treatment

Leukemia is a cancer of the blood-forming cells. It starts in the bone marrow, the soft tissue in the center of bones where blood cells are made. The marrow makes too many abnormal white cells, and those crowd out the healthy red cells, platelets and normal white cells the body needs.

Acute lymphoblastic leukemia (ALL) is the most common cancer of childhood. It accounts for about 25 percent of all cancer diagnoses in children under 15. About 3,100 children and teens under 20 are diagnosed with ALL each year in the United States.

Acute myeloid leukemia (AML) is the other main type. About 20 percent of childhood leukemias are myeloid. The word "acute" in both names means the cells are immature and the disease moves quickly, so treatment starts within days.

The age curve for ALL is unusual and worth knowing. Incidence peaks sharply in children aged 1 to 4, at 76.3 cases per million per year. By age 10 the rate has fallen to 23.8 per million. That peak is about four times higher than the rate in infants, and about four times the rate in children aged 10 and older.

Across all children, ALL runs at roughly 40 cases per million per year in ages 0 to 14, and about 20 per million in ages 15 to 19.

Rates also differ by group. NCI reports the highest incidence in Hispanic children and adolescents, at 46.8 cases per million, and in American Indian or Alaska Native children, at 43.9 per million. Incidence is substantially higher in White children than in Black children, with roughly double the rate between ages 1 and 4.

Down syndrome is a recognized risk factor for both ALL and AML.

Two numbers taken on the first day sort most children into a risk group. For B-cell ALL, NCI's classification is simple to state:

• Standard risk: white blood cell count under 50,000 per microliter, and age 1 to under 10 years.
• High risk: white blood cell count of 50,000 per microliter or higher, or age 10 or older, or both.

That is only the starting point. Teams then adjust the intensity of treatment using the immunophenotype (whether the leukemia is B-cell or T-cell), the genetics of the leukemia cells, and how fast the leukemia clears in the first weeks.

One genetic finding changes the plan immediately. If the cells carry the BCR::ABL1 fusion, also called Philadelphia chromosome-positive, a targeted drug is added to induction. Imatinib and dasatinib are the two NCI names as examples. These belong to a class called tyrosine kinase inhibitors.

Response is measured with a test called minimal residual disease, or MRD. It looks for leukemia cells that a microscope would miss, at levels far below 1 in 100. NCI states that genetic findings combined with MRD results can define groups of children with event-free survival above 95 percent, and other groups with rates of 50 percent or lower. The same disease name covers both.

Treatment of childhood ALL typically involves chemotherapy given for 2 to 3 years. It runs in phases:

• Remission induction, given at diagnosis, to clear the marrow of visible leukemia.
• Consolidation, sometimes called intensification, to attack what remains.
• Maintenance, a long, lower-intensity stretch of mostly oral medicine that takes up most of those years.

Two places in the body get their own treatment regardless of whether leukemia is found there. They are called sanctuary sites, because ordinary chemotherapy given by mouth or vein does not reach them well. The two that matter in childhood ALL are the central nervous system and the testes.

About 3 percent of children have leukemia detectable in the spinal fluid at diagnosis. NCI defines that category, CNS3, precisely: a spinal fluid sample with 5 or more white blood cells per microliter containing leukemia cells, or the presence of cranial nerve palsies. Overt testicular involvement is found in about 2 percent of boys at diagnosis.

Here is the reason every child gets CNS-directed treatment anyway. Without therapy aimed at the nervous system, most children eventually develop overt leukemia there, whether or not it was detectable at the start.

Low blood counts and a suppressed immune system are expected consequences, not complications. NCI states that adequate facilities for blood support and for treating infection must be immediately available through every phase of therapy. That is why families are told to call about a fever rather than wait it out, and why the treating center wants to hear before an urgent care visit.

The mortality figures for treatment are small but real, and worth having straight. Approximately 1 to 3 percent of children die during the remission induction phase. Another 1 to 3 percent die after reaching complete remission, from complications of treatment.

The change over five decades is one of the clearest success stories in medicine.

For ALL, the 5-year survival rate rose from 60 percent to approximately 90 percent for children younger than 15 between 1975 and 2020. For adolescents aged 15 to 19, it rose from 28 percent to more than 75 percent. For AML over the same period it rose from under 20 percent to 69 percent in children under 15, and to 72 percent in teens 15 to 19.

One caution about numbers you may find online. SEER's overall figure for acute lymphocytic leukemia, 73.2 percent 5-year relative survival for cases from 2016 to 2022, covers all ages. Adults with ALL do considerably worse than children, which pulls that combined figure well below the childhood rate. When you read a survival percentage, check the age range it describes.

Most children with ALL are treated on or according to a clinical trial protocol. NCI notes that trials are generally available, with separate protocols for standard-risk and higher-risk children, and that the opportunity to enroll is offered to most families. Our page on clinical trials for children explains how that works and what enrolling does and does not mean.

Treatment does not stop mattering when the last dose is given. NCI states that childhood and adolescent cancer survivors need close monitoring, because side effects of therapy can persist or first appear months or years later. For AML specifically, NCI names an increased risk of growth failure, gonadal and thyroid problems, cataracts, and second cancers.

Long-term follow-up is a defined part of the plan, not an optional extra. Ask the team for a written survivorship summary listing every drug given, the total doses, any radiation, and the schedule of checks that follows from them.

For the broader picture of childhood cancer, see our overview. For leukemia across all ages, see our page on leukemia.

• Call 911 or go to an emergency department if bleeding will not stop after ten minutes of firm pressure, if your child is working hard to breathe while sitting still, or if you cannot rouse your child properly.
• Call the oncology line immediately, day or night, if a thermometer reads 100.9°F (38.3°C) once, or 100.4°F (38.0°C) and stays there for an hour. These are the readings Together by St. Jude uses. While your child is on treatment, a fever like this is a medical emergency, not a wait-and-see. Ring the oncology line first rather than driving to a walk-in clinic. If nobody picks up quickly, take your child to an emergency department and say at the desk that they are having chemotherapy.
• Call your care team the same day if your child has shaking chills, drenching sweats, a stiff neck, pain on peeing, or is vomiting and keeping nothing down.
• Call your care team within a day or two if you see fresh bruises with no bump behind them, pinpoint dark-red spots under the skin, gums that ooze when brushed, or new bone or joint pain. Do the same if your child has gone pale and is short of breath climbing stairs they managed last week.

• NCI PDQ on childhood ALL, for doctors
• NCI PDQ on childhood AML, for doctors
• SEER stat facts on acute lymphocytic leukemia
• NCI PDQ on childhood ALL, patient version
• Fever and Signs of Infection, Together by St. Jude