Skip to main content

Health library

Back to health library

Understanding radiation therapy

Radiation therapy uses high-energy particles or waves to destroy or damage cancer cells.

Radiation therapy—also known as radiotherapy, x-ray therapy or irradiation—is one of the most common treatments for cancer. According to the American Cancer Society, more than half of people with cancer receive some form of radiation therapy.

Radiation therapy may be used before, during or after surgery; in combination with chemotherapy or another cancer treatment; or on its own. It can shrink tumors to make other treatments more effective, destroy cancer cells left behind after other treatments, or help relieve symptoms such as pain or pressure.

How it's given

Radiation therapy may be given from outside or inside the body.

External radiation is given most often. It uses a machine outside the body to deliver radiation to the site of the cancer. The type of radiation machine that's best for a given case depends on the type of cancer and its location.

For internal radiation, radioactive material is swallowed, injected or placed directly in the body. The material may be sealed in a small holder such as a wire, plastic tube or capsule. Radiation may also be given during surgery, when it can be placed directly into the tissue from which the tumor was removed.

Where it's done

External radiation therapy is usually done during regular visits to a hospital or treatment center. Treatments are usually done over many weeks, sometimes twice a day for several weeks.

Internal radiation therapy often requires a hospital stay.

Side effects

Side effects from radiation therapy vary. Some people have no side effects or only minor ones. In other cases, side effects may be more serious.

The seriousness and type of side effects depend on a person's general health, the part of the body that's being treated and the dose of radiation that's used.

For example, people who have radiation treatment to the head may have hair loss. People who have radiation treatment to the intestines may have problems with eating and digestion.

Many side effects can be effectively relieved with the right treatment or with a break or change in treatment.

Your doctor or nurse will explain the side effects you may have and the treatments that can help.

What you can do

If you're receiving radiation treatments, take care of yourself by getting plenty of rest and eating a healthful diet. You should also be very gentle with the skin in the area that's being treated. These tips from the National Cancer Institute can help:

  • Wash with warm water instead of hot water.
  • Pat the area dry instead of rubbing it.
  • Avoid tight clothing.
  • Don't rub, scrub or scratch the skin.
  • Don't place heating pads or ice packs on the treated skin.
  • Ask your doctor or nurse about when and what types of powders, creams, lotions, body oils or perfumes are safe to use.
If you're having unexpected or severe side effects, or if you're interested in emotional or social support groups, talk to your doctor or nurse.

Reviewed 3/4/2023

Related stories