Plain-language information about radiation therapy for cancer: what it is, what to expect, and how to get the most from your care.
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Radiation therapy (also called radiotherapy) uses high-energy X-rays or other types of radiation to treat cancer. The radiation damages the DNA inside cancer cells, preventing them from growing and dividing.
Modern radiotherapy is highly targeted. Treatment is carefully planned to deliver a precise dose to the cancer while minimising exposure to surrounding healthy tissue.
Radiotherapy can be used:
Most radiotherapy is delivered from outside the body (external beam radiotherapy). Some treatments are given internally (brachytherapy), where a radiation source is placed close to or inside the tumour.
Your first appointment is a consultation with your radiation oncologist. Nothing is done to you at this visit. It is purely a discussion.
What to bring: A referral letter from your doctor, your Medicare card, any relevant imaging or scans, and a list of your current medications including any allergies. Consider bringing a family member or friend for support, and write down any questions beforehand.
What will happen: Your radiation oncologist will review your diagnosis, imaging and pathology, explain whether radiotherapy is recommended and why, discuss the goals of treatment (curative, adjuvant or palliative), and outline the likely benefits and possible side effects. You will have the opportunity to ask questions and take time to consider your options before deciding whether to proceed.
If you decide to go ahead with radiotherapy, your team will coordinate the next steps from there.
Once you decide to proceed, radiotherapy involves several steps before treatment even begins:
1. CT simulation: A dedicated planning CT scan is taken with you in your exact treatment position. Previous scans cannot be used for this purpose. You may be fitted with an immobilisation device (mask or mould). Small permanent reference marks (tattoos, about the size of a freckle) are placed on your skin. This session takes approximately 30–45 minutes.
2. Treatment planning: Your radiation oncologist, physicists and dosimetrists design your personalised treatment plan, carefully mapping the tumour and surrounding normal structures. This takes several days and happens behind the scenes.
3. Treatment: Radiotherapy is delivered daily (Monday to Friday). Each session takes approximately 10–20 minutes, mostly positioning time. The beam itself takes only a few minutes and is completely painless. Radiation therapists leave the room during treatment but monitor you continuously via camera and intercom. Simply raise your hand or call out if you need them.
4. On-treatment reviews: You will see your radiation oncologist or registrar weekly to check for side effects and review your progress.
5. Follow-up: After treatment ends, scheduled appointments monitor your response and manage any lasting effects.
Side effects depend on the area of the body being treated, the dose and your individual health. Your radiation oncologist will discuss the specific risks relevant to your treatment before you start.
General (applicable to many treatment areas):
Side effects vary by treatment site:
Most side effects are temporary and resolve after treatment. Your team will advise you on how to manage them and when to seek help.
It is always worth preparing questions before your appointments. Here are some to consider:
There are no wrong questions. Your radiation oncology team is there to support you.
Myth: Radiotherapy is always painful.
Fact: The radiation beam itself is painless. You cannot feel it during treatment. Some people experience discomfort from positioning, and side effects may cause discomfort over time, but the treatment itself is not painful.
Myth: You become radioactive after external beam radiotherapy.
Fact: External beam radiotherapy does not make you radioactive. You are safe to be around others, including children, during and after treatment. (Internal treatments such as certain brachytherapy or radioisotope treatments may have specific precautions; your team will advise you.)
Myth: Radiotherapy always causes severe side effects.
Fact: Side effects vary widely depending on the area treated, the dose and the person. Many people complete radiotherapy with manageable side effects and continue their normal activities. Your team works to minimise side effects through careful planning.
Myth: Once cancer has spread, radiotherapy is not useful.
Fact: Radiotherapy has an important role in advanced and metastatic cancer. It can effectively relieve pain from bone metastases, treat brain metastases, and in some cases, treat a limited number of metastases with curative intent (e.g., SABR for oligometastatic disease).
Artificial intelligence is increasingly used in cancer care to assist with tasks such as:
It is important to understand that AI in medicine acts as a tool to assist your clinical team, not replace it. All treatment decisions are made and reviewed by qualified doctors and health professionals.
AI outputs require expert interpretation. Your radiation oncologist remains responsible for your care and is trained to apply AI tools critically and safely.
If you have questions about how AI might be used in your care, please ask your treating team. Transparency is important.
Your treating cancer care team is always the best source of advice about your individual situation.