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Radiation Therapy for Cancer

Treatment Overview

Radiation therapy uses high energy rays, such as X-rays, to destroy cancer cells and shrink tumours in different parts of the body. It is used to treat many types of cancer.

Radiation damages the genetic material of cancer cells, which stops their growth. Radiation may also damage normal cells that are close to the cancer cells. But normal cells usually repair themselves, while the cancer cells cannot.

Side effects from radiation therapy are a problem. Usually the side effects are temporary. But some side effects may be permanent. To treat the cancer, enough radiation needs to be given. But researchers keep looking for ways to protect the normal cells around the area being treated with radiation. And with new technology, people getting radiation therapy have fewer problems than in the past.

There are two main ways that radiation is done. When it is given from a machine outside the body, it's called external beam radiation, or EBRT. When radiation is given inside the body, it's called internal radiation.

Some types of external radiation therapy include:

  • Conformal therapy.
  • Particle therapy.
  • Stereotactic radiation therapy.
  • Total body irradiation.

Some types of internal radiation include:

  • Brachytherapy.
  • Intraoperative radiation therapy.
  • Systemic radiation therapy.

You may hear the terms "fractionated" or "hypofractionated" radiation therapy. There is always a target total radiation dose. Sometimes the total radiation dose is given in a single treatment. Sometimes it's divided into a few treatments ("hypofractionated" radiation therapy). Sometimes a small dose is given each time, and there are many treatments ("conventionally fractionated" radiation therapy).

Radiation therapy may be given before surgery to shrink a tumour, such as with bladder cancer. Or it may be given during surgery or while you are getting chemotherapy. Or it may be given after other treatment, such as after surgery for breast cancer.

Radiation therapy may be given when a person with cancer is not well enough for other treatment, such as surgery. It's also used in hospice palliative care for advanced or metastatic cancer. For example, it can relieve pain by shrinking tumours in the bones.

Why It Is Done

Radiation therapy is used to destroy cancer cells and to shrink tumours.

How Well It Works

Radiation is one of the main treatments used to kill cancer cells. But it doesn't always cure cancer. Researchers continue to study safer and more effective ways to use radiation therapy to treat cancer.


Radiation therapy may shrink a tumour, give you relief from cancer symptoms, or possibly cure cancer. But it has risks for serious side effects. Your doctor will recommend radiation therapy if the doctor thinks that the benefit you may have from this treatment is greater than the risks.

Risks of radiation therapy during and right after treatment include:

  • Fatigue.
  • Nausea with or without vomiting.
  • Skin changes, such as flaking, peeling, or shrinking. Your skin may turn red or get darker. These changes are called radiation dermatitis.
  • Problems that are specific to the area being treated. One example is hair loss with radiation to the head or neck. Another example is urinary problems if the lower belly is radiated.

Most of these problems will go away soon after the treatment ends. Some side effects, such as skin damage, may last longer. And sometimes the side effects are permanent, such as when the salivary glands are damaged.

And sometimes side effects may show up months or years after radiation therapy. These can include:

  • Skin changes (from external radiation treatments).
  • Damage to the bowels that causes diarrhea and bleeding or an obstruction.
  • Chronic bladder or rectal irritation.
  • Vaginal scarring (vaginal fibrosis).
  • Memory loss.
  • Infertility (not able to get pregnant or get someone else pregnant).
  • Harm to your lungs or heart.
  • In rare cases, a second cancer caused by exposure to radiation.


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