Understanding External Radiation Therapy for Breast Cancer

What To Expect from External Breast Radiation Including Side Effects

Whole breast radiation
Whole breast radiation. Art @ Pam Stephan

Radiation therapy is used to stop the growth and division of cancer cells, and external beam radiation is one of the most common forms of radiation used in breast cancer

Let's learn more about external beam radiation for breast cancer including what to expect from a radiation session and potential side effects.

What is External Beam Radiation?

External beam radiation is usually given after breast-conserving surgery.

It may also be given after mastectomy, if the cancer is large or if cancer is found in the lymph nodes. It's usually given at least a month or so after surgery to allow the body to heal. 

The purpose of radiation is to kill off any straggling cancer cells that may remain after surgery to prevent breast cancer recurrence. 

External beam radiation therapy means that a machine directs the radiation towards the cancer. It's a painless process.

The amount of radiation given depends on the type of surgery a person had, and if the cancer has spread to the lymph nodes in the underarm. So radiation includes the breast tissue, but may also include the chest wall and underarm area.  

How Long Does It Take to Get External Beam Breast Radiation?

According to the American Cancer Society, breast radiation sessions generally occur 5 days a week for approximately 5 to 6 weeks. 

Can I Get Radiation On An Accelerated Schedule?


If you don't live near a clinic or hospital, ask your radiation oncologist about your options for accelerated treatments. This is called hypofractioned breast radiation and can be completed in three weeks, and maybe even less.

What to Expect During a Radiation Treatment Session

Your radiation oncologist will carefully plan your treatments to hone in on the best positions and dosage.

There will be a special appointment for a simulation session where you will lay down while images of the target area are taken. Tattoos or ink marks may be used to help locate the target's position. A molded pillow might be created to help you stay in position during treatments.

When actual treatments begin, wear loose clothing that is easy to remove. For each radiation session, you will change into a hospital gown and go into a special treatment room. While lying on a table with your molded pillow, your radiation therapists will help you get into position. During the treatment, your therapist will stand in a separate shielded room and operate the radiation machine.

Radiation will take from one to five minutes. You will change back into your clothing and go back to normal activities when all is said and done.

Potential Side Effects of Whole Breast Radiation

Whole breast radiation affects cancerous as well as healthy tissues — so side effects may occur. From most to least common, potential radiation side effects include:

  • Fatigue
  • Breast skin becomes sunburned and sensitive
  • Breast changes  — swelling, tenderness or heaviness
  • Numbness, tingling, or weakness in the shoulder, arm, or hand if nerves in the arm are damaged
  • If your radiation include your underarm area for treatment of lymph nodes, you may develop lymphedema (arm swelling). Gentle exercise can help reduce arm lymphedema.
  • Rare affects on other organs

Coping And Recovery from Whole Breast Radiation

As you go through treatment, keep in mind that your side effects are temporary and will taper off over time. Allow yourself time to rest and recover from fatigue, especially near the end of your treatments.

Wear loose layers of soft clothing to prevent skin irritation. Ask your doctor about skin treatments that you can use between treatments to promote healing.

Take warm showers and baths and use cool compresses on your skin, to soothe blistering and skin peeling.

Be gentle with yourself and pamper your skin during and after treatment. Most changes in your breast go away in six months to a year, after you have completed radiation treatment.


American Cancer Society.(2015). External Beam Radiation Therapy. Retrieved October 23rd 2015. 

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