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Radiation therapy

Radiation therapy (also known as radiotherapy) uses radiation to destroy cancer cells. Although radiation also damages normal cells, cancer cells are especially sensitive to its effects. This makes radiation therapy an effective treatment for many cancer types.

Radiation therapy can be used:

Radiation therapy involves a total dose of radiation, which is divided into smaller doses or fractions. Typically, one fraction is given each day over several days until the total dose is reached.

High doses of radiation can be aimed directly at the tumour, depending on where the tumour is and whether it has spread. This limits the amount of radiation that reaches healthy areas of the body.

Types of radiation therapy

There are two main types of radiation therapy – external and internal.  

The type of radiation therapy recommended to you will depend on the type and location of your cancer, your general health and other treatments you might have had.

External radiation therapy

External radiation therapy (called external beam radiation) uses a machine that beams radiation onto the tumour. The area that receives radiation is very precise, and this minimises the amount of radiation on surrounding healthy areas.

External radiation therapy is usually given 5 times per week (with a 2-day rest), and can continue for several weeks. Each exposure will take a few minutes. Some people might get radiation on a different schedule, such as twice a week for a fewer number of weeks.

There are different types of external radiation therapy including:

  • Intensity modulated radiation therapy (IMRT) – this treatment changes the intensity of the radiation beams in certain areas allowing for stronger doses to be aimed at certain parts of the tumour
  • Stereotactic radiosurgery (SRS) – this is radiation therapy not surgery, but allows a large dose of radiation to be given to a small tumour area precisely. This is usually used for brain tumours and can also be used outside the brain (stereotactic body radiation therapy or SBRT)

The treatment itself is painless. However, you will need to keep very still during the procedure, and this can feel uncomfortable. The treatment team will make every effort to ensure that you are as comfortable as possible. External radiation therapy does not make you radioactive.

Internal radiation therapy

Radiation therapy that is given internally is called brachytherapy. It involves giving radiation via a needle, catheter or another specialised device. The device stays in place from a few minutes to a few days. Depending on the treatment and the dose of radiation, you may need to stay in hospital or make a daily visit for treatment.

You may give off a small amount of radiation for a short time after internal radiation therapy. If this will only be for a few minutes, you will stay in a separate room for that time to prevent others being exposed to the radiation. If the radioactivity will last for longer, and you are allowed to leave the hospital, you will need to take some safety precautions. Certain people (e.g. pregnant women, children, adolescents) should not get too close to you until the radiation weakens. Your doctors will discuss this with you in more detail.

Side effects of radiation therapy

The 2 most common side effects of radiation therapy are:

  • skin problems, especially at the radiation site, such as dryness, itchiness, peeling and blistering (similar to sunburn)
  • fatigue (tiredness).

Other potential side effects will depend on where radiation therapy is given in the body, and may include:

  • head or neck: dental problems, mouth problems (dryness, difficulty swallowing) or jaw stiffness
  • chest: stiffness in the area and some lung inflammation
  • stomach and belly: nausea, vomiting and diarrhoea
  • pelvis: diarrhoea, urination problems and reproductive problems. Having radiotherapy around the reproductive organs can affect fertility temporarily or permanently. You should discuss this with your doctor before your treatment if having children in the future is important to you.

For some people, radiation therapy causes few or no side effects. For others, the side effects are more severe. Side effects often begin during the second or third week of treatment. While most can be managed and will gradually disappear once treatment is finished, some may last for several weeks after treatment. Your treatment team may include allied health professionals including dietitians and speech therapists to assist with the side effects of radiotherapy.

If you feel unwell or have any unexpected side effects while you are having treatment, you should contact your doctor.

For more information about radiation and its side effects, you should talk to a member of your treatment team, or visit Treatment side effects.

Last updated 7 February 2025
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