Breast Cancer

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Treating Breast Cancer TOPICS

Radiation therapy for breast cancer

Radiation therapy is treatment with high-energy rays or particles that destroy cancer cells. Radiation to the breast is often given after breast-conserving surgery to help lower the chance that the cancer will come back in the breast or nearby lymph nodes. Radiation may also be recommended after mastectomy in patients either with a cancer larger than 5 cm, or when cancer is found in the lymph nodes.

Radiation is also used to treat cancer that has spread to other areas, for example to the bones or brain.

Radiation therapy can be given externally (external beam radiation) or internally (brachytherapy).

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.

The extent of radiation depends on whether mastectomy or breast-conserving surgery (BCS) was done and whether or not lymph nodes are involved.

If mastectomy was done and no lymph nodes had cancer, radiation is targeted at the chest wall and the places where any drains exited the body.

If BCS was done, most often the entire breast gets radiation, and an extra boost of radiation is given to the area in the breast where the cancer was removed to 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, radiation may be given to this area as well. In some cases, the area treated may also include supraclavicular lymph nodes (nodes above the collarbone) and internal mammary lymph nodes (nodes beneath the breast bone in the center of the chest).

When given after surgery, external radiation therapy is usually not started until the tissues have been able to heal, often a month or longer. If chemotherapy is to be given as well, radiation therapy is usually delayed until chemotherapy is complete.

Before your treatments start, the radiation team will take careful measurements to determine 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 that they will use later as a guide to focus the radiation on the right area. You might want to ask your health care team if these marks will be permanent.

Lotions, powders, deodorants, and antiperspirants can interfere with external beam radiation therapy, so your health care team may tell you not to use them until treatments are complete.

External radiation therapy is much like getting an x-ray, but the radiation is more intense. 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.

Breast radiation is most commonly given 5 days a week (Monday through Friday) for about 5 to 6 weeks.

Some older women who have breast conserving surgery for early stage breast cancer don’t need radiation. (See “Treatment of invasive breast cancer, by stage.”)

Accelerated breast irradiation: The standard approach of getting external radiation for 5 days a week over many weeks can be inconvenient for many women. Some doctors are now using other schedules, such as giving slightly larger daily doses over only 3 weeks.

Giving radiation in larger doses using fewer treatments is known as hypofractionated radiation therapy. This approach was studied in a large group of women who had been treated with breast conserving surgery (BCS) and who did not have cancer spread to underarm lymph nodes.

When compared with giving the radiation over 5 weeks, giving it over only 3 weeks was just as good at keeping the cancer from coming back in the same breast over the first 10 years after treatment. Newer approaches now being studied give radiation over an even shorter period of time. In one approach, larger doses of radiation are given each day, but the course of radiation is shortened to only 5 days. Intraoperative radiation therapy (IORT) is another approach that gives a single large dose of radiation 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 below, under “Brachytherapy.” It is hoped that these approaches may prove to be at least equal to the current, standard breast irradiation, but few studies have compared these new methods directly to standard radiation therapy. It is not known if all of the newer methods will still be as good as standard radiation after many years, so many doctors still consider them experimental. 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, and 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 up to 2 years.

In some women, the breast becomes smaller and firmer after radiation therapy. Having radiation may also affect your options for breast reconstruction later on. It can also raise the risk of problems if it is given after reconstruction, especially tissue flap procedures. Women who have had breast radiation may have problems breastfeeding later on. Radiation to the breast can also 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 therapy of axillary lymph nodes also can cause lymphedema. (See "What happens after treatment for breast cancer?")

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 angiosarcoma. (See "What is breast cancer?") 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, radioactive seeds or pellets are placed into a device in the breast tissue in the area where the cancer had been. It can be used along with external beam radiation in patients who had breast conserving surgery (BCS) 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). Tumor size, location, and other factors may limit who can get 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 and is considered a form of accelerated partial breast irradiation. 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: 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 the right 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) is placed down through the tube and into the device for a short time and then removed. Treatments are 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 breast conserving surgery (BCS) had promising results, but didn’t directly compare this technique with standard whole breast external beam radiation.

One study that compared outcomes between intracavitary brachytherapy and whole breast radiation after BCS found that women treated with brachytherapy were twice as 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.

This study raises questions about whether irradiating only the area around the cancer will reduce the chances of the cancer coming back as much as giving radiation to the whole breast. More studies comparing the 2 approaches are needed to see if brachytherapy should be used instead of whole breast radiation.

Intracavitary brachytherapy can also have side effects, including redness, bruising, breast pain, infection, and a break-down of an area of fat tissue in the breast. As with whole breast radiation, weakness and fracture of the ribs can also occur.

For more information about radiation therapy, see the Radiation Therapy section of our website.

Last Medical Review: 09/25/2014
Last Revised: 02/22/2016