Radiation Therapy for Breast Cancer


What is radiation therapy?

Radiation therapy (radiotherapy) uses high-energy X-ray beams or internal radiation (brachytherapy) to damage cancer cells. Damaged cancer cells can’t multiply and grow.

You receive this treatment from a radiation oncologist, a doctor who specializes in radiation therapy.

How does radiation therapy treat breast cancer?

Most people with breast cancer get radiation therapy after breast cancer surgery (lumpectomy or mastectomy). The treatment kills cancer cells that may remain after surgical removal of the tumor. Your healthcare provider may call this adjuvant radiation therapy.

When does someone with breast cancer get radiation therapy ?

The timing for radiation therapy depends on several factors. The treatment may take place:

  • After a lumpectomy: A lumpectomy removes the cancerous tumor, leaving most of the breast. Radiation therapy lowers your risk of cancer coming back in the remaining breast tissue or nearby lymph nodes as well as reduces your chance of passing away of breast cancer.
  • After a mastectomy: Most people don’t get radiation therapy after a mastectomy (complete breast removal). Your provider may recommend radiation if the tumor was larger than 5 cm (about 2 inches); if there’s cancer in surrounding lymph nodes, skin tissue or muscle; or if all the cancer can't be removed (positive margins).
  • Before surgery: Rarely, healthcare providers use radiation to shrink a tumor before surgery.
  • Instead of surgery: Sometimes, providers use radiation therapy to shrink a tumor that they can’t surgically remove (unresectable). A tumor may be unresectable due to its size or location. Or you may not be a candidate for surgery because of concerns about your health.
  • To treat cancer spread: Stage 4 breast cancer is cancer that spreads (metastasizes) to other parts of the body. Your provider may use radiation therapy to treat cancer that spreads to other parts of the body.

If you had surgery, radiation therapy typically starts about one month after the incision heals if chemotherapy is not received. Some individuals receive chemotherapy after surgery, followed by radiation therapy. You may get the two treatments at the same time.

What are the types of radiation therapy for breast cancer?

There are different ways to receive radiation therapy. Your healthcare provider will choose the best method based on the cancer location, type and other factors.

Types of radiation therapy for breast cancer include:

  • External beam whole-breast irradiation: During external beam whole-breast radiation therapy, a machine called a linear accelerator sends beams of high-energy radiation to the involved breast. Most people get whole-breast radiation five days a week for one to six weeks. The time frame depends on factors including lymph node involvement. In some cases, intensity-modulated radiation therapy (IMRT) may be used.
  • External beam partial-breast: This treatment directs radiation to the tumor site only, not the entire breast over 1 to 3 weeks with 3-dimensional conformal radiation or IMRT.
  • Brachytherapy: Some people get internal radiation therapy or brachytherapy. Your provider places an applicator or catheter. A radioactive seed (about the size of a grain of rice) is moved into the tumor site. The seeds give off radiation for several minutes before your provider removes them. You receive two treatments every day for five days.
  • Intraoperative: Intraoperative radiation therapy (IORT) takes place in the operating room before your provider closes the surgical site. Your provider delivers a high dose of radiation to the tumor area of the exposed breast tissue.

Who should not get radiation therapy for breast cancer?

Radiation therapy isn’t safe for pregnant women.

You can get radiation on other parts of the body; in some cases, radiation can be given to the treated area again.

Procedure Details

What should I expect before radiation therapy for breast cancer?

Most people who have breast cancer treatment receive external beam radiation therapy. The goal is to destroy any remaining cancerous cells while protecting healthy tissue.

Before your first treatment, you will have a planning session (also called a simulation). This simulation helps your provider map out the treatment area while sparing normal tissues (for example, heart and lung). This session may take one hour or longer.

During the simulation, your provider:

  1. Carefully positions your body in an immobilization device on the treatment table. This device helps you stay in the correct position for all treatments.
  2. Uses techniques to reduce the dose to the heart and lungs (for example, deep inspiratory breath hold or Active Breathing Coordinator)
  3. Uses a tattoo device to mark the corners of the treatment areas (treatment fields). The freckle-sized tattoos are permanent. These markings help your provider align the radiation treatment in the same manner each time.

What steps should I take before radiation therapy?

Follow your healthcare provider’s recommendations. In general, you should not:

  • Discuss which vitamins you take with your provider

How is radiation therapy for breast cancer performed?

Most people lie on their back during the treatment though some breast treatments are performed while lying on your stomach (prone breast radiation). You place your arm above your head (the arm on the same side as the affected breast).

During the treatment, your treatment team:

  • Positions and secures your body in the immobilization device. If you had a mastectomy, your provider might place a bolus (flat piece of wet towel or rubber) on top of the treatment area to increase the radiation dose to the surface.
  • Lines up the machine (linear accelerator) with the first treatment field. To protect themselves from radiation exposure, providers leave the room. Your provider can still hear and see you.
  • Turns on the machine. You will hear a whirring noise, but you won’t see the radiation beams. You must remain still. Depending on the radiation type and dose, treatment can take 30 seconds to several minutes.
  • Returns to the room to position the machine to treat a different treatment field. Most people get treatment on two to five fields each day.
  • Takes daily/weekly X-rays (port films) of the treatment field to make sure the radiation is hitting the correct area.

What should I expect after radiation therapy for breast cancer?

You may notice fatigue as well as skin changes while undergoing radiation therapy. Your skin may become irritated, tender and swollen (radiation dermatitis). People with fair skin may develop a red sunburn appearance. People with dark skin may notice darkening of the skin. This condition can also cause dry, itchy, flaky skin. Your skin may peel as you get close to finishing treatments (desquamation). This skin irritation is temporary. Your provider can prescribe creams or medications to ease discomfort, if needed.

Skin discoloration can persist after treatment ends. Some people with fair skin have a slight pink or tan appearance for several years. You may also see tiny blood vessels (telangiectasias) in the radiated area. These vessels look like thin red lines or threads. These are not cause for concern.

Care at Cleveland Clinic

Risks / Benefits

What are the potential side effects of radiation therapy for breast cancer?

Besides skin changes, you may experience these short-term side effects while undergoing treatment:

Long-term side effects may include:

  • Changes in breast size (smaller or larger) and sensitivity.
  • Lymphedema of the breast or arm.
  • Skin changes, such as darker, thickened skin or larger pores.

What are the potential risks or complications of radiation therapy for breast cancer?

Rarely, radiation therapy to the breast affects the chest area. Potential complications include:

Recovery and Outlook

How effective is radiation therapy?

If early-stage breast cancer hasn’t spread, radiation therapy after a lumpectomy significantly reduces the risk of cancer coming back by approximately 50%. Studies show that a lumpectomy followed by radiation therapy is as effective as a mastectomy without radiation therapy.

People who undergo a lumpectomy have a 20% to 40% chance of the cancer coming back at 10 to 20 years. With the addition of postsurgical radiation therapy, that risk drops to 5% to 10%. However, there are some patients who derive less benefit from radiation including patients 65 years or older with small cancers.

When to Call the Doctor

When should I call the doctor?

You should call your healthcare provider if you experience:

  • Chest pain.
  • Severe skin or breast inflammation.
  • Signs of infection, such as fever, chills or weeping skin wounds.

A note from Cleveland Clinic

Radiation therapy can lower the risk of cancer recurrence and cancer spread. The treatment affects everyone differently. Most side effects go away in a few months after treatments end. Some problems last longer. You should tell your healthcare provider about any problems you have while getting treatment. Your provider may change the therapy slightly to minimize issues while still effectively treating the cancer.

Last reviewed by a Cleveland Clinic medical professional on 03/19/2021.


  • American Cancer Society. Radiation Therapy for Breast Cancer in Men. (https://www.cancer.org/cancer/breast-cancer-in-men/treating/radiation-therapy.html) Accessed 3/1/2021.
  • American Cancer Society. Radiation for Breast Cancer. (https://www.cancer.org/cancer/breast-cancer/treatment/radiation-for-breast-cancer.html) Accessed 3/1/2021.
  • American Cancer Society. Radiation Therapy Side Effects. (https://www.cancer.org/treatment/treatments-and-side-effects/treatment-types/radiation/effects-on-different-parts-of-body.html) Accessed 3/1/2021.
  • American Society of Clinical Oncology. Breast Cancer: Types of Treatment. (https://www.cancer.net/cancer-types/breast-cancer/types-treatment) Accessed 3/1/2021.
  • BreastCancer.org. External Beam Radiation. (https://www.breastcancer.org/treatment/radiation/types/ext/expect/daily_routine) Accessed 3/1/2021.
  • BreastCancer.org. Brachytherapy or Internal Radiation. (https://www.breastcancer.org/treatment/radiation/types/internal) Accessed 3/1/2021.
  • BreastCancer.org. Radiation After Lumpectomy Offers Long-Term Benefits. (https://www.breastcancer.org/research-news/20111019) Accessed 3/1/2021.
  • BreastCancer.org. Radiation Therapy. (https://www.breastcancer.org/treatment/radiation) Accessed 3/1/2021.
  • BreastCancer.org. Radiation Therapy Side Effects. (https://www.breastcancer.org/treatment/radiation/skin/reactions) Accessed 3/1/2021.
  • National Breast Cancer Foundation Inc. Radiation Therapy. (https://www.nationalbreastcancer.org/breast-cancer-radiation-therapy) Accessed 3/1/2021.
  • Radiological Society of North America. Breast Cancer Treatment. (https://www.radiologyinfo.org/en/info.cfm?pg=breast-cancer-therapy) Accessed 3/1/2021.

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy