Radiation for Breast Cancer

Some women with breast cancer will need radiation, often in addition to other treatments. The need for radiation depends on what type of surgery you had, whether your cancer has spread to the lymph nodes or somewhere else in your body, and in some cases, your age. You may have just one type of radiation, or a combination of different types.

Radiation therapy is treatment with high-energy rays (such as x-rays) or particles that destroy cancer cells. There are 2 main types of radiation therapy that can be used to treat breast cancer:

  • External beam radiation: This type of radiation comes from a machine outside the body.
  • Internal radiation (brachytherapy): For this treatment, a radioactive source is put inside the body for a short time.

When might radiation therapy be used?

Not all women with breast cancer need radiation therapy, but it may be used in several situations:

  • After breast-conserving surgery (BCS), to help lower the chance that the cancer will come back in the breast or nearby lymph nodes
  • After a mastectomy, especially if the cancer was larger than 5 cm (about 2 inches), or if cancer is found in the lymph nodes
  • If cancer has spread to other parts of the body, such as the bones or brain

External beam radiation

This is the most common type of radiation therapy for women with breast cancer. The radiation is focused from a machine outside the body on the area affected by the cancer.

Which areas need radiation depends on whether mastectomy or breast-conserving surgery (BCS) was done and whether or not the cancer has reached nearby lymph nodes.

  • If you had a mastectomy and no lymph nodes had cancer, radiation is targeted at the chest wall and the places where any drains exited the body after surgery.
  • If you had BCS, you will most likely have radiation to the entire breast, and an extra boost of radiation to the area in the breast where the cancer was removed to help prevent it from coming back in that area. The boost is often given after the treatments to the whole breast have ended. It uses the same machine, but the beams are aimed at the place where the cancer was removed. Most women don’t notice different side effects from boost radiation than from whole breast radiation.
  • If cancer was found in the lymph nodes under the arm (axillary lymph nodes), radiation may be given to this area as well. In some cases, the area treated may also include the nodes above the collarbone (supraclavicular lymph nodes) and the nodes beneath the breast bone in the center of the chest (internal mammary lymph nodes).

When will I get radiation therapy?

If you will need external radiation therapy after surgery, it is usually not started until the tissues have a chance to heal, which is often a month or longer. If you are getting chemotherapy as well, radiation treatments are usually delayed until chemotherapy is complete.

Preparing for external beam radiation therapy

Before your treatments start, the radiation team will take careful measurements to figure out the correct angles for aiming the radiation beams and the proper dose of radiation. They will make some ink marks or small tattoos on your skin to be used as a guide to focus the radiation on the right area. Check with your health care team whether the marks they use will be permanent.

External radiation therapy is much like getting an x-ray, but the radiation is stronger. The procedure itself is painless. Each treatment lasts only a few minutes, but the setup time—getting you into place for treatment—usually takes longer.

Types and schedules of external beam radiation

The traditional schedule for getting breast radiation has been 5 days a week (Monday through Friday) for about 5 to 6 weeks. But many doctors are now using accelerated breast irradiation to give larger doses over a shorter time. There are several different types of accelerated breast irradiation:

  • Hypofractionated radiation therapy: In this approach, radiation is given in larger doses using fewer treatments – typically for only 3 weeks. In women treated with breast conserving surgery (BCS) and without cancer spread to underarm lymph nodes, this schedule has been shown to be just as good at keeping the cancer from coming back in the same breast as giving the radiation over 5 weeks. It might also lead to fewer short-term side effects. In a newer approach now being studied, larger doses of radiation are given each day, but the course of radiation is shortened to only 5 days.
  • Intraoperative radiation therapy (IORT): In this approach, a single large dose of radiation is given in the operating room right after BCS (before the breast incision is closed). IORT requires special equipment and is not widely available.
  • 3D-conformal radiotherapy: In this technique, the radiation is given with special machines so that it is better aimed at the area where the tumor was. This allows more of the healthy breast to be spared. Treatments are given twice a day for 5 days. Because only part of the breast is treated, this is considered to be a form of accelerated partial breast irradiation. (Other forms of accelerated partial breast irradiation are described under “Brachytherapy.”)

Researchers hope these approaches will prove to be at least equal to the current, standard radiation therapy methods, but few studies have compared them directly to standard radiation therapy. It is not known if all of the newer methods will have the same long-term results as standard radiation, so not all doctors use them. Women who are interested in these approaches may want to ask their doctor about taking part in clinical trials of accelerated breast irradiation now going on.

Possible side effects of external radiation

The main short-term side effects of external beam radiation therapy to the breast are:

  • Swelling and heaviness in the breast
  • Skin changes in the treated area
  • Fatigue

Skin changes can range from mild redness to blistering and peeling. Your health care team may advise you to avoid exposing the treated skin to the sun because it may make the skin changes worse. Most skin changes get better within a few months. Changes to the breast tissue usually go away in 6 to 12 months, but it can take longer.

External beam radiation therapy can also cause side effects later on:

  • Some women may find that radiation therapy causes the breast to become smaller and firmer.
  • Radiation may affect your options for breast reconstruction later on. It can also raise the risk of problems if it’s given after reconstruction, especially tissue flap procedures.
  • Women who have had breast radiation may have problems breastfeeding later on.
  • Radiation to the breast can sometimes damage some of the nerves to the arm. This is called brachial plexopathy and can lead to numbness, pain, and weakness in the shoulder, arm, and hand.
  • Radiation to the underarm lymph nodes can cause lymphedema, a type of pain and swelling in the arm or chest.
  • In rare cases, radiation therapy may weaken the ribs, which could lead to a fracture.
  • In the past, parts of the lungs and heart were more likely to get some radiation, which could lead to long-term damage of these organs in some women. But modern radiation therapy equipment allows doctors to better focus the radiation beams, so these problems are rare today.
  • A very rare complication of radiation to the breast is the development of another cancer called an angiosarcoma. These rare cancers can grow and spread quickly.


Brachytherapy, also known as internal radiation, is another way to deliver radiation therapy. Instead of aiming radiation beams from outside the body, a device containing radioactive seeds or pellets is placed into the breast tissue for a short time in the area where the cancer had been.

For women who had breast-conserving surgery (BCS), brachytherapy can be used along with external beam radiation as a way to add an extra boost of radiation to the tumor site. It may also be used by itself (instead of radiation to the whole breast) as a form of accelerated partial breast irradiation. Tumor size, location, and other factors may limit who can get brachytherapy.

Types of brachytherapy

There are different types of brachytherapy:

  • Interstitial brachytherapy: In this approach, several small, hollow tubes called catheters are inserted into the breast around the area where the cancer was removed and are left in place for several days. Radioactive pellets are inserted into the catheters for short periods of time each day and then removed. This method of brachytherapy has been around longer (and has more evidence to support it), but it is not used as much anymore.
  • Intracavitary brachytherapy: This is the most common type of brachytherapy for women with breast cancer. A device is put into the space left from BCS and is left in place until treatment is complete. There are several different devices that can be used, including MammoSite, SAVI, Axxent, and Contura. They all go into the breast as a small catheter (tube). The end of the device inside the breast is then expanded so that it stays securely in place for the entire treatment. The other end of the catheter sticks out of the breast. For each treatment, one or more sources of radiation (often pellets) are placed down through the tube and into the device for a short time and then removed. Treatments are typically given twice a day for 5 days as an outpatient. After the last treatment, the device is collapsed down again and removed.

Early studies of intracavitary brachytherapy as the only radiation after BCS have had promising results, but they didn’t directly compare this technique with standard whole breast external beam radiation.

One study that compared outcomes after BCS found that women treated with brachytherapy were more likely to go on to get a mastectomy of the treated breast (most likely because cancer was found again in that breast). The overall risk was still low, however, with about 4% of the women in the brachytherapy group needing mastectomy versus only 2% of the women in the whole breast radiation group. More studies comparing these approaches are now in progress.

Possible side effects of intracavitary brachytherapy

As with external beam radiation, intracavitary brachytherapy can have side effects, including:

  • Redness
  • Bruising
  • Breast pain
  • Infection
  • Breakdown of an area of fat tissue in the breast
  • Weakness and fracture of the ribs in rare cases

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master’s-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

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Last Medical Review: June 1, 2016 Last Revised: August 18, 2016



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