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

Side Effects of Radiation Therapy

Radiation therapy to the breast can cause some side effects. Some begin during treatment. Others may occur months or even years later.

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 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).

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

Learn about Komen support resources.

Learn more about support groups.

Short-term side effects

Most often, side effects from radiation therapy begin within a few weeks after starting treatment [9]. Once radiation therapy ends, short-term side effects will mostly go away within 2 weeks [9].

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

Pain and skin changes

During and just after treatment, your treated breast may be sore. Talk with your health care provider about using mild pain relievers such as ibuprofen, naproxen or acetaminophen 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 provider may suggest special creams to ease this discomfort.

Sometimes the skin peels further and the area becomes tender and sensitive. This is called a moist reaction. It’s most common in the skin folds and the underside of the breast.

If a moist reaction 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 [10-11].

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

Regular exercise, even just walking for 20 minutes every day, may help reduce fatigue [10,12-14]. Getting a good night’s sleep is also important.

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

Learn more about fatigue and insomnia.

Long-term side effects  

Breast and skin changes

Over time, your breast may become firmer or smaller.

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.


People who have radiation therapy to the lymph nodes in the collarbone or underarm area (axillary nodes) or who have axillary nodes removed may develop lymphedema.

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

The chances of getting lymphedema are greater if your treatment includes both [5,15-18]:

  • Removal of axillary nodes during breast cancer surgery (the more nodes removed, the greater the risk)
  • Radiation therapy to the axillary or supraclavicular (above the collarbone) lymph nodes

Being overweight also increases the risk of lymphedema [5,15-17].

Learn more about lymphedema.

Rare short-term side effects

Nausea and hair loss

Nausea is rare with radiation therapy to the breast.

You won’t lose the hair on your head. However, you may lose some hair under your arm 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 small [19].

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 treatment 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.

The most common cancers linked to radiation therapy are sarcomas (cancers of the connective tissue) [20-22]. For women who are long-term smokers, radiation therapy may also increase the risk of lung cancer [19].

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


  • If you or a loved one needs more information about breast health or breast cancer, call the Komen Breast Care Helpline at 1-877 GO KOMEN (1-877-465-6636). All calls are answered by a trained specialist or oncology social worker in English and Spanish, Monday through Friday from 9:00 a.m. to 10:00 p.m. ET. You can also email the helpline at  
  • We offer an online support community through our closed Facebook Group – Komen Breast Cancer group. The Facebook group provides a place where those with a connection to breast cancer can discuss each other’s experiences and build strong relationships to provide support to each other. Visit Facebook and search for “Komen Breast Cancer group” to request to join the closed group.
  • Our fact sheets, booklets and other education materials offer additional information.

Updated 05/19/21