by EBSCO Medical Review Board

Radiation therapy is a method used to kill cancer cells. The goal is to try and kill as much cancer as possible. It works 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 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 © 2002 Nucleus Communications, Inc. All rights reserved.

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 fewer side effects. The 3-D types may not available everywhere.

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 (catheter) is placed and secured where a tumor was removed. The device is left in place until the course of radiation is done. This is the more common method.
  • Interstitial—Tubes are placed in 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
  • Problems 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. It is important to talk to the care team as soon as these appear. Problems can be better controlled when addressed early.


Breast cancer. Merck Manual Professional Version website. Available at: Accessed March 24, 2022.

Breast cancer in women. EBSCO DynaMed website. Available at: Accessed March 24, 2022.

Intensity-modulated radiation therapy (IMRT). Radiology Info—Radiological Society of America website. Available at: Accessed March 24, 2022.

Radiation for breast cancer. American Cancer Society website. Available at: Accessed March 24, 2022.

Radiation therapy for metastatic breast cancer. EBSCO DynaMed website. Available at: Accessed March 24, 2022.

Treatment option overview. National Cancer Institute website. Available at: Accessed March 24, 2022.

What is 3D conformal radiation therapy? UPMC Hillman Cancer Center website. Available at: Accessed March 24, 2022.

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