Last updated: 12 March 2026
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Radiation therapy for breast cancer
Also known as radiotherapy, radiation therapy uses a controlled dose of radiation to kill cancer cells or damage them so they cannot grow, multiply or spread. The radiation is usually in the form of x-ray beams. It does not cause you to become radioactive during the period of treatment. Radiation therapy may be recommended:
- after breast-conserving surgery – usually a part of standard treatment
- after a mastectomy – you may have radiation to the chest wall and lymph nodes above the collarbone, and sometimes lymph nodes next to the breastbone
- if the sentinel node has cancer cells – you may have radiation to the armpit instead of ALND
- after neoadjuvant chemotherapy and before surgery.
- after adjuvant chemotherapy.
You will usually start radiation therapy within 8 weeks of surgery. If you’re having chemotherapy after surgery, radiation therapy will begin about 3–4 weeks after chemotherapy has finished.
Planning radiation therapy
Treatment is carefully planned to cause the most harm to the cancer cells and to limit damage to the surrounding healthy tissues. Planning involves several steps, which may occur over a few visits.
You will have a planning session at the radiation therapy centre. During this appointment, you will have a planning CT scan of the area to be treated.
Sometimes marks are put on your skin so the radiation therapists can ensure you are lined up correctly each time you are treated. These marks are usually small dots (tattoos), and they may be temporary or permanent.
Talk to your radiation therapists if you are worried about these tattoos. Invisible tattoos are available in some centres. If you have had breast-conserving surgery, the surgeon can sometimes place tiny markers (called fiducial markers) in your breast tissue to show where the cancer used to be. This helps the radiation oncology team to deliver the radiation therapy more precisely.
You may be asked to try a deep inspiration breath hold (DIBH) technique. This involves taking and holding a deep breath for 20–30 seconds during treatment. DIBH helps to inflate the lungs and move the heart away from the radiation field, reducing the risk of heart damage.
Having radiation therapy
You will probably have radiation therapy daily from Monday to Friday for 1–6 weeks. Most people have radiation therapy as an outpatient and go to the treatment centre each day.
Each radiation therapy session will be in a treatment room. Setting up the machine can take 10–30 minutes, but the actual treatment takes only 1–5 minutes. You will lie on a table under the machine and your breast will be exposed. The radiation therapist will leave the room and then switch on the machine, but you can talk to them through an intercom. Radiation therapy is not painful, but you will need to lie still while it is given. Most people will be lying on their back with their arms up. If DIBH is recommended for you, the radiation beam will only be turned on when you are in the DIBH position.
If you are having radiation therapy at a private centre, Medicare will cover some of the cost, but your private health insurance may not, so you may have to pay some of the cost yourself (out-of-pocket costs). If you are worried about the cost, speak to your treatment team about having treatment in a public hospital.
Side effects of radiation therapy
Radiation therapy may cause the following side effects:
Skin problems
You may have some redness around the treated area. The skin may become dry and itchy, blister, or become moist and weepy. It usually returns to normal 4–6 weeks after radiation therapy ends. Sometimes skin can become very irritated or peel (radiation dermatitis). You may need dressings, or special creams or gels, to help the area heal.
Tiredness
You may start to feel tired 1–2 weeks after radiation therapy begins. Fatigue usually gets better a few weeks after treatment finishes.
Aches
You may feel minor aches or shooting pain in the breast area during or after radiation therapy. It should ease over time.
Swelling
Some people have swelling or fluid build-up in the breast (breast oedema or lymphoedema) that can last for up to a year or longer. Radiation therapy to the armpit increases the risk of swelling in the arm (lymphoedema).
Hair loss
Radiation therapy to the breast won’t make you lose the hair on your head, but you will usually lose hair from the treated armpit.
Other side effects
Late effects can develop months or years after radiation therapy. Part of the lung behind the treatment area may become inflamed, causing a dry cough or shortness of breath. There is a slight risk of heart problems, but this usually happens only if you have treatment to your left breast or if you smoke. Hardening of tissues (fibrosis) may happen months or years after treatment. In rare cases, radiation therapy may cause a second cancer.
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Sources and references
This information has been developed by Cancer Council NSW on behalf of all other state and territory Cancer Councils and Cancer Council Australia as part of a National Cancer Information Subcommittee initiative. We thank the reviewers of this content: Dr Diana Adams, Medical Oncologist, Macarthur Cancer Therapy Centre, NSW; Prof Bruce Mann, Specialist Breast Surgeon and Director, Breast Cancer Services, The Royal Melbourne and The Royal Women’s Hospitals, VIC; Dr Shagun Aggarwal, Specialist Plastic and Reconstructive Surgeon, Prince of Wales, Sydney Children’s and Royal Hospital for Women, NSW; Andrea Concannon, consumer; Jenny Gilchrist, Nurse Practitioner Breast Oncology, Macquarie University Hospital, NSW; Monica Graham, 13 11 20 Consultant, Cancer Council WA; Natasha Keir, Nurse Practitioner Breast Oncology, GenesisCare, QLD; Dr Bronwyn Kennedy, Breast Physician, Chris O’Brien Lifehouse and Westmead Breast Cancer Institute, NSW; Lisa Montgomery, consumer; A/Prof Sanjay Warrier, Specialist Breast Surgeon, Chris O’Brien Lifehouse, NSW; Dr Janice Yeh, Radiation Oncologist, Peter MacCallum Cancer Centre, VIC. We also thank the health professionals, consumers and editorial teams who have worked on previous editions of this title.
Photographs have been reproduced with permission from A/Prof James French, Westmead Breast Cancer Institute, NSW; Prof Elisabeth Elder, Westmead Breast Cancer Institute and The University of Sydney, NSW; and Breast Cancer: Taking Control, breastcancertakingcontrol.com © Boycare Publishing, 2010.
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