Radiotherapy factsheet


Radiotherapy is also known as radiation therapy. It is a type of cancer treatment that sends high doses of radiation to specific body parts to:

  • shrink cancer cells
  • destroy cancer cells
  • relieve symptoms when cancer is very advanced and cannot be treated.

Radiation is energy that moves from one place to another. Very high doses of radiation can cause damage to cells, like burns. 

In radiotherapy, high levels of radiation are targeted specifically at cancer cells. This radiation shrinks or destroys the cancer cells, stopping them from growing and spreading. 

Damaged, healthy cells nearby will usually recover quickly after each radiation dose.

Radiotherapy is different from another common cancer treatment called chemotherapy.

In chemotherapy, a mixture of medicines is given to kill cancer cells throughout the body. In radiotherapy, cells will only be damaged in the area where the radiation is given.

Preparing for treatment

Your child's treatment team will give you information about:

  • special instructions on how to prepare
  • where to go
  • what to wear
  • how long the therapy will take.

Each course of radiotherapy is planned specifically for your child by the radiotherapy team. 

Let your child's doctor know if you have any questions about the radiotherapy.

Radiation mask or mould

Your child may need a mask or mould of the body part that will be treated.

Masks and moulds for radiotherapy help keep your child’s body in the correct position during treatment. They are made to fit your child’s head or body exactly and have tiny holes so your child can see through.

Sedation and fasting

Some children can become anxious or frightened when their heads and faces are covered. They may need some extra help getting through the scan. 

This can include:

  • having a general anaesthetic – medicine that puts your child to sleep during treatment
  • being sedated – medicines that relax your child but are not as strong as a general anaesthetic.

General anaesthetic and certain types of sedation will require your child to fast nil by mouth. Fasting nil by mouth means no eating or drinking, usually 2 hours before the scan. 

Fasting nil by mouth helps prevent aspiration, which is life-threatening. Aspiration is when food or water is brought up into the lungs during a procedure.

Let your child’s treatment team know if you think they will struggle to wear a radiation mask so they can organise support or sedation.

CT planning scan

Children going through radiotherapy will have a CT planning scan. This scan takes pictures of the parts of the body that are getting the radiotherapy to make sure the dose is given in the correct position. 

During treatment

Parents, carers and other support people cannot be in the treatment room during radiotherapy. This is because the doses of radiation are extremely high and harmful to others.

Your child can see and speak to the radiation therapist or nurse outside the room during treatment.

Radiotherapy will not make your child radioactive, and it is safe for them to interact with other people immediately after treatment has finished for the day. 

Radiotherapy treatments generally happen in three stages:


Your child will lie very still under a machine called a simulator.

The simulator takes exact measurements of the body part that is being treated.

The radiation therapist or nurse will make temporary ink marks on your child’s skin for reference lines.


Your child will lie very still under a machine called a linear accelerator. 

The linear accelerator sends a beam of radiation straight into the area of the body that needs treatment, marked by the reference lines. 

Your child might hear a buzzing sound while the machine is working. This will take 3-5 minutes and should not cause any pain.


A radiation oncologist will review your child’s progress regularly during the treatment and talk to you about their progress as much as possible.

The radiation oncologist is a specialist cancer doctor who oversees radiotherapy.

Side effects and pain

Side effects from radiotherapy can be different depending on which part of the body is going through treatment. 

Some common side effects are:

  • nausea and vomiting
  • feeling very tired 
  • loss of appetite
  • dry, red, or itchy skin 
  • dry mouth and cough
  • sore throat
  • hair loss
  • digestive problems.

Most side effects will go away after treatment.

Speak to your child’s treatment team about support for managing side effects and let them know as soon as possible if your child has any pain during treatment.

Length of treatment

Radiotherapy usually involves multiple treatments that can be given:

  • once or twice a day
  • over several days
  • over several weeks.

With each treatment, more cancer cells die while the healthy cells have time to recover. 

Your child’s treatment team will plan the timing of the radiotherapy carefully to avoid causing damage to healthy cells where possible.

After treatment

After the treatment finishes, your child will have regular check-ups with their doctor to check:

  • that immediate side effects have settled down
  • how the cancer has responded to the treatment
  • whether there are any signs the cancer has come back.

It may take some time after treatment has finished to know whether it has worked.

After a few years, your child’s doctor will focus on checking growth and development and looking out for any late side effects of the cancer treatment. 


Long-term side effects of cancer treatment

Some side effects from radiotherapy can be permanent.

These include:

  • differences in the appearance and texture of skin and hair
  • changes to how their bowel and bladder work
  • changes to hearing and vision
  • weaker bones.

Radiotherapy only affects the area of the body that is going through treatment. 

Any permanent changes to other body parts that are not being treated are unlikely to be caused by radiotherapy and should be checked by a doctor.

Survivorship care aims to provide emotional support while identifying and managing any side effects as early as possible throughout your child’s life.

Speak to your child’s treatment team about survivorship clinics after treatment finishes.

When to see your doctor

Your child's treatment team will give you contact information for any questions or concerns about your child's health while at home between treatments. 

If your child has any of the following symptoms during treatment, call Triple Zero (000) for an ambulance or go to the emergency department:

  • difficulty breathing 
  • convulsions or seizures
  • signs of infection
  • fever
  • looking extremely unwell. 

Support for families

A cancer diagnosis can leave families and children feeling overwhelmed, scared, anxious, and upset. Practical and emotional support during and after treatment is essential and can come from: 

  • family
  • friends
  • healthcare professionals
  • specialised support services.

Speak to your child’s treatment team for information about support services.

Last updated Monday 25th March 2024


This factsheet is provided for general information only. It does not constitute health advice and should not be used to diagnose or treat any health condition.

Please consult with your doctor or other health professional to make sure this information is right for you and/or your child.

The Sydney Children’s Hospitals Network does not accept responsibility for inaccuracies or omissions, the interpretation of the information, or for success or appropriateness of any treatment described in the factsheet.

© Sydney Children’s Hospitals Network 2024