What Are the Side Effects of Breast Cancer Radiation Therapy?

Breast cancer radiation therapy can cause temporary side effects such as skin irritation, tiredness, breast swelling and shoulder stiffness. These effects often build during treatment and may briefly worsen after the final session before improving. The article explains how to care for yourself, which longer-term changes to report and when to contact your cancer care team.

Breast cancer radiation therapy uses carefully planned radiation to treat the breast, chest wall or nearby lymph node areas. It is often given after surgery to reduce the risk of cancer returning in the treated area. At NCCS, our radiation oncology team plans each treatment around the individual’s diagnosis, surgery and overall treatment plan.

If you are about to begin treatment, it is normal to have questions about breast cancer radiation therapy side effects. Most side effects are temporary and affect only the part of the body receiving radiation. Some may build gradually over the course of treatment, and a few can appear months or years later. Knowing what to look out for helps you manage your cancer journey better and you can get support early when needed.

Key Takeaways

• Skin changes and tiredness are among the most common short-term breast cancer radiation therapy side effects.
• Side effects often build gradually during treatment and may briefly worsen after the final session before they begin to improve.
• The breast or chest area may feel swollen, tender, warm or firmer for a period after radiation therapy.
• Treatment to the underarm or lymph node areas can increase the risk of arm or breast swelling, known as lymphoedema.
• Your care team should know about any new, worsening or worrying symptoms so they can assess and treat them promptly.

Why Does Breast Radiation therapy Cause Side Effects?

Radiation therapy uses high-energy X-rays to damage cancer cells so that they can no longer grow and divide. Although the treatment is targeted, healthy cells in the treatment area can also be affected. Healthy cells usually repair themselves more effectively than cancer cells, which is why many side effects improve with time.

The exact side effects vary from person to person. They can depend on:

• The part of the breast or chest area being treated
• Whether lymph nodes near the collarbone or underarm are included
• The total dose and number of treatment sessions
• Whether you have had breast-conserving surgery or a mastectomy
• Previous or ongoing treatments, such as chemotherapy or hormone therapy
• Your skin type, general health and healing after surgery

Radiation therapy teams use detailed scans and planning techniques to direct radiation as accurately as possible. If treatment is being given to the left breast or chest wall, techniques such as deep inspiration breath hold may be used in suitable patients to help reduce radiation exposure to the heart.

Common Short-Term Side Effects

Short-term effects often begin after the first few treatment sessions. They may become more noticeable towards the end of treatment or in the one to two weeks afterwards. This does not necessarily mean that treatment has gone wrong. Radiation effects can continue after the final session before the body starts to recover.

Skin changes in the treatment area

The skin of the breast, chest wall, underarm or upper chest may become red, darker, dry, itchy or tender. Some people describe it as feeling similar to sunburn. In people with darker skin, colour changes may be more noticeable as darkening rather than redness.

The skin can also become more sensitive in areas where there is friction or moisture, such as beneath the breast or in the underarm. In some cases, it may peel or become sore.

Your radiation therapist or nurse will give you specific skincare advice. It is important to use only products approved by your team on the treated area. They may recommend a moisturiser, dressing or other treatment if the skin becomes sore.

Tiredness

Tiredness during radiation therapy is different from simply feeling sleepy after a busy day. It can feel like low energy, heaviness or a lack of motivation that does not fully improve after resting.

Going for daily treatment appointments, disrupted sleep, emotional stress and other cancer treatments can all add to fatigue. A gentle routine can help. Short walks, light stretching, regular meals and planned rest periods are often more manageable than trying to push through exhaustion or staying in bed all day.

Let your care team know if fatigue is affecting your ability to eat, sleep, work or manage daily activities. They can check for other causes, such as anaemia, pain, infection or low mood.

Breast or chest wall swelling and tenderness

The treated breast may feel swollen, heavy, warm or tender. If you have had breast-conserving surgery, the breast can temporarily look or feel different from the untreated side. If you have had a mastectomy, the chest wall may feel tight, sensitive or uncomfortable.

These changes often settle gradually, but the timeline is different for everyone. Wearing a supportive, non-wired bra or soft clothing may feel more comfortable while the area is tender.

Changes around the nipple and hair loss in the treatment area

The nipple or surrounding skin may become dry, sensitive or darker. Hair in the underarm or on the upper chest can also thin or fall out if these areas are within the treatment field. Hair loss in the treated area may be temporary, but in some cases it can be long-lasting.

Shoulder stiffness or reduced arm movement

Surgery, radiation therapy and the need to keep one arm raised during treatment can all contribute to stiffness. You may notice tightness across the chest, shoulder or underarm, especially if lymph nodes are included in treatment.

Your doctor, nurse or physiotherapist may advise gentle exercises to maintain shoulder movement. Do not force through sharp pain, and ask your team before starting a new exercise routine.

What May Happen and When?

This general timeline can help you understand what to expect, but your own recovery may be different.

Less Common or Longer-Term Effects

Most people do not develop serious long-term problems from breast radiation therapy. However, it is useful to know what may occur so that you can report changes early.

Changes in breast size, shape or firmness

Over time, the treated breast may feel firmer or look slightly different in size or shape. This may be related to scarring within the breast tissue, sometimes called fibrosis. It can be more noticeable after treatment to a larger area or after surgery.

A change in how the breast feels does not automatically mean that cancer has returned. Still, it should be mentioned at your follow-up appointments so your team can assess it properly.

Lymphoedema

Lymphoedema is swelling caused by a build-up of lymph fluid. It can affect the arm, hand, breast or chest wall. The risk is higher when lymph nodes in the underarm or around the collarbone have been removed or treated with radiation therapy.

Signs can include a feeling of heaviness, tightness, puffiness, aching or swelling in the arm, hand, breast or chest area. Early assessment is helpful. Your team may refer you to a lymphoedema specialist for advice on exercise, skin care, compression garments or other support.

Changes in skin colour or texture

Some people have lasting darkening, lightening or increased sensitivity in the treated area. Small blood vessels may become more visible, and the skin may feel less stretchy. Protecting the area from strong sun exposure can help reduce further irritation or colour changes.

Effects on the lungs, ribs or heart

Radiation therapy to the breast or chest area can expose a small part of the lung to radiation. Rarely, this can cause inflammation in the lung, which may lead to a dry cough or shortness of breath. Rib tenderness or a rib fracture is uncommon but can occur.

Treatment to the left breast can also expose part of the heart to radiation. Modern planning aims to keep this exposure as low as possible. Your radiation oncologist will explain the measures used in your treatment plan and any factors that matter in your case.

Looking After Yourself During Radiation therapy

You do not need to manage side effects alone. Bringing up even a minor change during your review can help your team prevent it from becoming more uncomfortable.

These practical steps may help during breast cancer radiation therapy:

• Wash the treated skin gently with lukewarm water and pat it dry instead of rubbing.
• Use moisturisers, creams, deodorants or dressings only as recommended by your radiation team.
• Choose soft, loose clothing that does not rub the breast, underarm or chest wall.
• Avoid exposing the treated area to direct sun, heat packs, hot water bottles or very hot baths.
• Rest when you need to, but include light movement if you feel able.
• Eat regular meals and drink enough fluids, especially if tiredness affects your appetite.
• Continue the shoulder or arm exercises recommended by your care team.
• Tell your team about pain, sleep difficulties, anxiety or practical concerns such as transport and work arrangements.

When Should You Speak to Your Doctor or Radiation Team?

You do not have to wait for your next appointment if something feels wrong. Contact your care team if you have:

• Skin that becomes very painful, blistered, weeping or broken
• A fever or feeling unwell alongside redness, warmth or swelling of the breast or chest area
• New swelling, heaviness or tightness in the arm, hand, breast or chest wall
• Pain that is not controlled by medicines
• A new or worsening cough, chest pain or shortness of breath
• Increased difficulty in moving your shoulder or arm
• Low mood, anxiety or exhaustion that is making daily life difficult

Seek urgent medical attention if you develop sudden chest pain, severe breathlessness, coughing up blood, or symptoms that feel like a medical emergency.

Will Every Person Have the Same Side Effects?

No. Some people have only mild skin changes or tiredness, while others need more support with soreness, swelling or fatigue. The absence of side effects does not mean the radiation therapy is not working, and more severe side effects do not mean the treatment is more effective.

It is also important not to compare your experience too closely with someone else’s. Breast cancer treatment is personalised. Your surgery, radiation field, medicines and health history may be different from another person’s.

Managing Breast Cancer Radiation therapy Side Effects With the Right Support

Breast cancer radiation therapy side effects can feel unsettling, especially when they build gradually after treatment begins. Most short-term effects, including tiredness and skin irritation, improve over the weeks after radiation therapy ends. Longer-term changes are less common, but they should still be discussed with your care team.

At NCCS, our radiation oncologists, radiation therapists, nurses and allied health professionals support patients before, during and after radiation therapy. If you are preparing for treatment or have concerns about side effects, speak with your care team. You can also find out more about breast cancer and the care available at NCCS.

Frequently Asked Questions

1. Can I shower during breast radiation therapy?
   Most people can shower as usual using lukewarm water and a mild product recommended by their care team. Avoid scrubbing the treated area, and pat it dry gently. Your team may give different advice if your skin becomes broken or needs a dressing.
   
   
2. Can I use deodorant on the treated underarm?
   Ask your radiation therapist or nurse first. Advice can vary depending on whether the underarm is in the treatment area and the condition of your skin. If you are advised to use deodorant, avoid applying it.
   
   
3. Is it safe to be around children or pregnant people after radiation therapy?
   External beam radiation therapy does not make you radioactive. You can be safely around children, pregnant women, family members and pets after each treatment session.
   
   
4. Can radiation therapy affect a breast reconstruction?
   Radiation therapy can affect how reconstructed breast tissue heals or changes over time. The impact depends on the type and timing of reconstruction. Your breast surgeon and radiation oncologist can explain how this applies to your treatment plan.
   
   
5. When can I return to work after breast radiation therapy?
   Some people continue working during treatment, while others need time away because of fatigue, travel or skin soreness. The right timing depends on your job, energy levels and other treatments. Discuss work arrangements with your doctor or nurse if you need medical documentation or support.
   
   
6. Can I have a mammogram after breast radiation therapy?
   Follow-up mammograms remain important after breast-conserving surgery and radiation therapy. Your team will tell you when to schedule them based on your treatment and follow-up plan. Tell the imaging centre that you have had breast cancer treatment, as the breast treated may look and feel different on examination.