Side effects from radiation therapy to the breast

During radiation therapy to the breast, you may experience different short-term side effects.

What are the possible short-term side effects?

Radiation therapy to the breast may cause a number of short-term side effects. However, everyone is different and you’re unlikely to experience all of the same side effects as someone who is receiving the same treatment as you.

If you’re concerned about any side effects during your radiation therapy treatment to the breast, we encourage you to speak with your care team who can help you with strategies to manage your side effects.

Types of short-term side effects

Swelling, aches and pains in the breast area

You may notice mild swelling in the breast or under your arm. This is normal and will improve when treatment finishes. Please talk to your care team if the swelling gets worse or is uncomfortable. It’s not uncommon to feel minor twinges or pain in the breast area. This will also improve once treatment is completed.

Moderate swelling can persist six to eight weeks after treatment and can be uncomfortable. Mild swelling may persist for up to one year or more. Please advise your care team if you notice any swelling in your arm or hand during treatment.

Sore throat

You may develop a mild sore throat if your neck is in the treatment field. Tell your nurse if you are experiencing a sore throat.

Increased firmness

Mild to moderate firmness can occur in the treated breast, and remain for up to eight weeks after treatment. This doesn’t usually require intervention.

Skin reaction

Two to three weeks after treatment starts your skin may become red, itchy or irritated. This reaction can last the remainder of your treatment, and usually returns to normal four to six weeks after treatment finishes.

Towards the end of treatment, the skin reaction can become more intense and may continue to increase for up to two weeks after treatment finishes. You may experience some minor skin loss in the armpit, under the breast, in the nipple or neck area. This can be managed with a simple dressing until the area heals.

Your nurses will show you how to care for your skin during treatment and manage any skin reactions. Tell your nurse if you’re worried about a skin reaction or if you experience any skin changes.


You may feel tired or lack energy for daily activities during your treatment. You may feel increasingly tired as you reach the end of your treatment. This is a common reaction to radiation therapy and each person is usually affected to varying degrees. Fatigue usually eases a few weeks after treatment finishes. Finding a balance between rest and activity will help you manage daily life.

How can I manage skin changes?

Moisturise twice a day

Your care team will recommend a cream to help manage any skin changes. At the start of your treatment, apply cream to the area being treated twice a day. As treatment progresses, you may need to apply the cream three to four times per day. Do not apply cream within the hour prior to your treatment, as cream needs to be well absorbed. Let your nursing team know if you continue to experience skin changes.

Wash with warm water and pat dry

You may wash the skin that is being treated with warm water and a mild non-perfumed soap. Pat dry the skin – do not rub.

Wear loose fitting clothing

Avoid wearing tight fitting clothing that could potentially rub or irritate the skin. You may find singlets, cotton ‘crop-tops’ or loose fitting bras more comfortable. Avoid underwire or lace bras.

Avoid excessive temperatures

Avoid exposing the treatment area to excessive temperature including direct sunlight, heat packs, ice packs, saunas or hot spas during the course of your radiation therapy.

Do not shave or use deodorants or talcum powder under the arm on the side being treated. Do not apply sunscreen to the treatment area.


Lymphoedema is swelling of the arm and/or other limb caused when the lymphatic system does not function properly. Over time this swelling increases and can lead to a feeling of heaviness and discomfort in the area. If left untreated, it can lead to reduced mobility and function.

Secondary lymphoedema can result from damage to the lymphatic vessels and/or lymph nodes. This may be from surgery, the lymph nodes being removed, and/or radiation therapy. There are effective treatment programs that can reduce the swelling and risk of complications. Your nurses can assist with management techniques and teach you how to self-manage your lymphoedema at home.

The earlier lymphoedema is recognised, the better we are able to help you manage it. We may also refer you to a lymphoedema specialist if required.

Learn more about lymphoedema


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