The Who, What, Where, When and Sometimes, Why.

Side Effects of Radiation Therapy

Radiation therapy to the breast can cause side effects. Some begin during treatment. Others may not occur until months or even years later.

Before you begin radiation therapy, talk with your health care provider about possible side effects and how to manage them.

Easing worries about radiation therapy

It’s normal to worry about possible side effects of radiation therapy.

Talk with your health care provider about your concerns.

Your health care provider may be able to suggest a hospital social worker, patient navigator, psychologist or support group to help ease anxiety related to radiation therapy (or breast cancer).

Learn about Susan G. Komen® support resources.

Learn more about support groups and other types of social support.

Learn about healthy ways to cope with stress.

You will not be radioactive

You will not be radioactive when you leave the radiation treatment center after any standard radiation therapy session. You will not pose any radiation risk to your family or your pets.

Short-term side effects

Most often, side effects from radiation therapy begin within a few weeks after starting treatment [10]. Once radiation therapy ends, short-term side effects will mostly go away within 2 weeks [10].

Let your radiation oncologist or nurse know how the sessions are making you feel. They may be able to recommend things, such as creams, to lessen the side effects.

Pain and skin changes

During and just after radiation therapy, your treated breast may be sore. Talk with your health care provider about using mild pain relievers such as ibuprofen (Advil or Motrin), naproxen (Aleve or Naprosyn) or acetaminophen (Tylenol) to ease breast tenderness.

The treated breast may also be rough to the touch, red (like a sunburn), swollen and itchy. Sometimes the skin may peel, as if sunburned. Your health care provider may suggest special creams to ease this discomfort.

Sometimes the skin peels further and the area becomes tender and sensitive. It’s most common in the skin folds and the underside of the breast. If this occurs, let your radiation team know. They can give you creams and pads to make the area more comfortable until it heals.

Learn more about easing pain related to radiation therapy.

Learn about long-term skin changes due to radiation therapy


Fatigue is common during radiation therapy and may last for several weeks after treatment ends.

Fatigue is mainly a short-term problem, but for some, it can persist [11-12].

You may feel like you don’t have any energy and may feel tired all the time. Resting may not help.

Regular exercise, even just walking for 20 minutes every day, may help reduce fatigue [12-15]. Getting a good night’s sleep is also important.

Talk with your health care provider if you’re fatigued or have insomnia (problems sleeping).

Learn more about fatigue and insomnia.

Long-term side effects  

Breast and skin changes

Over time, your breast may feel firmer or it may become smaller or larger.

You may also have mild tanning of the skin where the breast was treated, or red discoloration, especially around the surgical scar(s). These changes may be permanent.


Lymphedema is a condition in which fluid collects in the arm or hand, causing it to swell. Swelling may also occur in the breast, chest or back.

People who have radiation therapy to the lymph nodes in the underarm area (axillary lymph nodes) or to those above the collarbone (supraclavicular lymph nodes) may develop lymphedema [6,16-19].

The chances of getting lymphedema are greater if your treatment also includes removal of axillary lymph nodes during breast cancer surgery (the more nodes removed, the greater the risk) [6,16-19].

Being overweight also increases the risk of lymphedema [6,16-19].

Learn more about lymphedema.

Rare short-term side effects


Nausea is rare with radiation therapy to the breast.

Hair loss

You won’t lose the hair on your head. However, you may lose some hair in the underarm area or on the breast or chest area getting radiation (this may be a concern for some men with breast cancer).

Rare long-term side effects

Although rare with modern treatment, the side effects below may occur a few months or years after radiation therapy.

Rib fracture

Rib fracture can occur when the radiation weakens the rib cage near the treatment area. This is rare with modern treatment.

Heart problems

If radiation therapy is given to the left side of the chest, heart problems may develop years later.

Many techniques are now used to limit this risk. With modern radiation therapy, the risk of heart problems is usually very low [20].

Lung problems

Radiation pneumonitis is an inflammation of the lungs that can cause shortness of breath, a dry cough and low-grade fever. It’s rare with modern radiation therapy and almost always goes away with treatment.

Anti-inflammatory drugs can often relieve symptoms.

Nerve problems

Brachial plexopathy can happen when radiation damages nerves in the upper chest. It may cause permanent tingling, pain and weakness in the affected hand and arm.

Nerve problems are very rare with modern treatment.

Radiation therapy and risk of a second cancer

In rare cases, radiation therapy to the breast can cause a second cancer.

Although the most common cancers linked to radiation therapy are sarcomas (cancers of the connective tissue), they are very rare [21-22].

For women who smoke, radiation therapy may also increase the risk of lung cancer [20].

The risk of a second cancer is very small. If your radiation oncologist recommends radiation therapy, the benefits of radiation therapy outweigh this risk.

Susan G. Komen® Support Resources

Updated 07/04/23