The information on this page was reviewed and approved by
Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was updated on September 29, 2021.

Radiation therapy for breast cancer

Radiation therapy uses high-energy X-rays or other forms of radiation to kill cancer cells. Breast cancer patients may receive one or a combination of radiation therapies that fit into two basic categories:

  • External beam radiation therapy
  • Accelerated partial breast irradiation

Radiation therapy is typically recommended for breast cancer patients after a tumor has been removed, to kill microscopic cancer cells that may have been left behind. Radiation therapy may also be used in combination with other therapies, such as chemotherapy or hormone therapy.

The length of radiation therapy treatment depends on a variety of factors, including the type of therapy used and the stage of the disease.

External beam radiation therapy (EBRT) 

The most common type of radiation therapy for breast cancer, EBRT is generally given after other treatments are complete.

In EBRT, a beam of radiation, a high-energy X-ray, is focused on the spot where the cancer was removed. If a lumpectomy was performed, a patient may receive EBRT to the entire breast, a technique called whole-breast radiation. EBRT may also be delivered to nearby lymph nodes.

Some advantages of EBRT for breast cancer patients may include:

  • It is fast, painless and performed as an outpatient procedure.
  • Unlike chemotherapy for breast cancer, which circulates throughout the body, EBRT is targeted to the treatment area.
  • At no point during radiation therapy is a patient radioactive, and there’s no risk of radioactivity to your friends and family.

The types of EBRT include:

Intensity modulated radiation therapy (IMRT)

Advanced software is used to plan a precise dose of radiation to the area where a tumor was removed. A computer-controlled device called a linear accelerator delivers radiation in sculpted doses that match the 3D geometrical shape of the target, including concave and complex shapes.

Advantages of IMRT for breast cancer may include:

  • IMRT employs an advanced computer program to map your radiation dosage in three dimensions.
  • IMRT directs radiation at the target and modulates the intensity of the radiation beams, helping to spare healthy tissue.

IMRT breast cancer radiation therapy may be used in conjunction with other treatments. It may be an appropriate option for those who have previously had breast cancer radiation therapy and are experiencing recurrent tumors in the treated area.

Accelerated partial breast irradiation (APBI)

This breast radiation therapy delivers focused radiation specifically to the part of the breast where the tumor was removed.

Some advantages of APBI for breast cancer may include:

  • Radiation is contained as much as possible to the tumor cavity.
  • Because the radiation is targeted, it affects less healthy tissue and organs close to the breasts, including the lungs, heart, ribs, muscles and skin.
  • It may be delivered in a more condensed schedule than some other radiation therapies for breast cancer.

Types of APBI include:

High-dose rate (HDR) brachytherapy

This type of internal radiation therapy delivers radiation from implants placed close to, or inside, the tumor(s) in the body.

Advantages of HDR brachytherapy for breast cancer may include:

  • It delivers a precise, highly concentrated dose of radiation directly to the area where the tumor was removed.
  • It limits radiation exposure to healthy surrounding breast tissue, reducing some of the side effects associated with standard radiation.
  • After a series of treatments, the catheters are removed and no radioactive materials are left in the body.


This breast-conservation therapy delivers a targeted dose of radiation directly to the tissue surrounding the tumor bed. Potential advantages of AccuBoost for breast cancer include:

  • The procedure is performed in an outpatient setting.
  • The targeted dose is designed to help contain the radiation treatment to the lumpectomy site as much as possible.
  • By delivering a measured dose that matches the size, shape and location of the target site, AccuBoost is designed to limit toxicity to the breast.
  • Providing targeted, measured, therapeutic doses is designed to produce fewer radiation-related side effects. 

Intraoperative radiation therapy (IORT)

  • IORT is performed during surgery immediately following the removal of a breast lump and before the lumpectomy incision is closed. A large dose of radiation is focused directly on the surgery site and is intended to be the only radiation therapy required for most patients. In some cases, additional EBRT therapy may be used.
  • A patient must be a surgical candidate in order to be eligible for breast cancer IORT. This treatment is generally reserved for patients with early-stage disease.

Side effects of radiation therapy for breast cancer

Radiation therapy for breast cancer may cause short-term or long-term side effects. Short term side effects of internal or external beam radiation include:
  • Redness or discoloration of the skin
  • Breast pain and/or swelling
  • Fatigue

Other long-term side effects of radiation for breast cancer include:

  • Changes to the feel or size of the breast
  • Difficulty breastfeeding
  • Nerve damage that may lead to weakness, numbness or pain
  • Damage to the lymph system resulting in lymphedema
  • Bone weakness and fractures
  • Damage to other organs exposed to radiation

Next topic: How is breast cancer treated with surgery?