Acute lymphoblastic leukemia (ALL): Radiation therapy

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Learn how radiation therapy is used to treat acute lymphoblastic leukemia (ALL).

Key points

  • A minority of children with acute lymphoblastic leukemia (ALL) will require radiation therapy if chemotherapy cannot adequately treat leukemic cells in the brain or testes.
  • Radiation uses ray beams to damage and destroy leukemic cells.
  • Radiation is fractioned into separate small daily treatments over a period of weeks.
  • Radiation has some short-term side effects.

A small percentage of children with Acute Lymphoblastic Leukemia (ALL) receive chemotherapy and radiation therapy to the brain, called cranial radiation therapy (CRT). Some boys may also need radiation to the testes. This is because chemotherapy medicines may not adequately treat leukemic cells in the brain or testes. Talk to your child’s doctor to see if your child requires radiation therapy.

If your child requires radiation therapy, you will meet with a pediatric radiation oncologist.

What is radiation therapy?

Radiation therapy is the use of high-energy X-ray or gamma ray beams. These rays damage or destroy leukemic cells. Radiation beams cannot be seen or felt.

The radiation will only affect the person who is having treatment. It is a form of energy, like heat or light that goes away very quickly when the energy source is removed. Your child is not “radioactive” and can continue life as usual.

How does radiation therapy work?

The radiation beam affects the cells’ ability to grow and divide. The goal of radiation treatment is to deliver an effective dose of radiation to leukemic cells – which may be the whole brain or testes, depending on your child’s situation. Fortunately, most normal cells recover from radiation more easily than leukemic cells.

Radiation therapy is fractionated. This means that the total dose of radiation is given in separate small treatments (fractions) each day from Monday to Friday over a period of weeks. The number of days of treatment needed depends on the total dose of radiation required to treat the leukemic cells in the central nervous system (CNS) or testes. The total dose is different for each child’s situation.

Cranial radiation therapy (CRT)

The proportion of patients that receive cranial radiation has decreased significantly over time. Cranial radiation is only given to patients considered to be at highest risk of subsequent CNS relapse. In patients who receive cranial radiation, the dose has been reduced and the spine is no longer irradiated.

Depending on a child’s age, CRT may be given to:

  • Treat leukemic cells in the CNS for patients who are CNS positive. Doctors check your child’s spinal fluid during every lumbar puncture to determine the number of leukemic cells in the fluid that bathes the brain and spine, called the cerebral spinal fluid (CSF).

Radiation to the testes

Sometimes, leukemia cells can hide inside the testes of boys. If your child still has evidence of leukemia in the testes after finishing the first phase of chemotherapy (induction), the doctor may use radiation therapy directly to the testes. This is known as testicular irradiation. Your child’s doctor would give radiation during the second month of chemotherapy (consolidation phase).

Short term side effects of radiation

Depending on the site of radiation, your child may experience some side effects. These include:

  • fatigue during and after radiation therapy
  • excessive sleepiness, which may be a condition called somnolence syndrome. This usually occurs after cranial radiotherapy.
  • hair loss or thinning
  • nausea and/or vomiting
  • headaches

For more information, please see Potential Late Effects of Acute Lymphoblastic Leukemia Treatment.

Last updated: March 6th 2018