Radiation therapy is a method used to kill cancer cells. The goal is to try and kill as much cancer as possible. It tends to work best when used with surgery and chemotherapy. Radiation is often used after surgery to kill any leftover cancer. It may also be used to shrink large tumors that are causing symptoms.

Radiation can be given in many ways. However, external beam is more used more often.

External Beam Radiation

A machine that is outside of the body makes the radiation. Short bursts of x-rays are aimed at the cancer.

Radiation is used:

  • After breast-saving surgery—to kill any cancer left behind
  • After mastectomy—if the tumor was 5 centimeters (cm) or more in size OR 4 or more lymph nodes under the arm were found with cancer
  • As comfort care for later stages of cancer

Radiation of a Tumor
Diagram of partial or segmental mastectomy

Copyright © Nucleus Medical Media, Inc.

Newer types of 3-dimensional (3-D) technology are intensity modulated treatment (IMRT) and conformal radiation therapy. The beams surround all sides of the tumor. More intense radiation is focused on the tumor. It also lowers the damage to healthy tissue around it. There are less side effects. The 3-D types may not be in all areas.

External beam radiation only takes a few minutes. The total time can range from 5 to 8 weeks. This will depend on the total dose that is needed. Most of the time, it is given 5 days a week. For some, a faster, more intense type may work better. This method is used less days a week and for a shorter amount of time.


Radioactive material is implanted inside the body near or in the cancer tumor.

Brachytherapy (or internal radiation) includes:

  • Intracavitary—A tube called a catheter is placed and secured where a tumor was removed. The device is left in place until the course of radiation is done. During this time, the tube can be seen because it sticks out of the breast. This is the more common method.
  • Interstitial—Tubes are placed into the breast near where a tumor was removed. Pellets are placed into the tube for a period of time each day. Then they are taken out. This is not used as often as it used to be.

Side Effects and Management

Radiation to the chest may cause:

  • Cough
  • Trouble breathing
  • Blood in the phlegm or spit
  • Chest pains
  • Inflammation of the lung tissue—radiation pneumonitis

There are many ways to manage these and other problems such as diarrhea or anemia. Talk to your care team as soon as these appear so they can be better controlled.


Breast cancer. Merck Manual Professional Version website. Available at: https://www.merckmanuals.com/professional/gynecology-and-obstetrics/breast-disorders/breast-cancer. Updated January 2018. Accessed March 11, 2019.

Breast cancer in women. EBSCO DynaMed Plus website. Available at:http://www.dynamed.com/topics/dmp~AN~T113654/Breast-cancer-in-women. Updated November 26, 2018. Accessed March 11, 2019.

Intensity-modulated radiation therapy (IMRT). Radiology Info—Radiological Society of America website. Available at: https://www.radiologyinfo.org/en/info.cfm?pg=imrt. Updated January 25, 2017. Accessed March 11, 2019.

Radiation for breast cancer. American Cancer Society website. Available at: https://www.cancer.org/cancer/breast-cancer/treatment/radiation-for-breast-cancer.html. Updated October 3, 2017. Accessed March 11, 2019.

Radiation therapy for breast cancer. EBSCO DynaMed Plus website. Available at:http://www.dynamed.com/topics/dmp~AN~T901113/Radiation-therapy-for-breast-cancer. Updated December 4, 2017. Accessed March 11, 2019.

Treatment option overview. National Cancer Institute website. Available at: https://www.cancer.gov/types/breast/patient/breast-treatment-pdq#section/_185. Updated February 6, 2019. Accessed March 11, 2019.

What is 3D conformal radiation therapy? UPMC Hillman Cancer Center website. Available at: http://hillman.upmc.com/cancer-care/radiation-oncology/treatment/external-beam/3d-conformal. Accessed March 11, 2019.

Last reviewed December 2018 by EBSCO Medical Review Board Mohei Abouzied, MD, FACP  Last Updated: 3/11/2019