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Radiation therapy is treatment with high-energy rays (or particles) that destroy cancer cells. Some women with breast cancer will need radiation, in addition to other treatments.

Depending on the breast cancer's stage and other factors, radiation therapy can be used in several situations:

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

Types of radiation therapy for breast cancer

The main types of radiation therapy that can be used to treat breast cancer are:

• External beam radiation therapy
• Brachytherapy

External beam radiation therapy (EBRT)

EBRT is the most common type of radiation therapy for women with breast cancer. A machine outside the body focuses the radiation on the area affected by the cancer.

Which areas need radiation depends on whether you had a mastectomy or breast-conserving surgery (BCS) and if the cancer has reached nearby lymph nodes.

• If you had a mastectomy and no lymph nodes had cancer cells, radiation will be focused on the chest wall, the mastectomy scar, 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 (called whole breast radiation). An extra boost of radiation to the area in the breast where the cancer was removed (called the tumor bed) is often given if there is a high risk of the cancer coming back. The boost is often given after the treatments to the whole breast have ended. It uses the same machine, with lower amounts of radiation aimed at the tumor bed. 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), this area may be given radiation, as well. Sometimes, the area treated might 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).

If you will need external beam radiation therapy after surgery, it is usually not started until your surgery site has healed, which often takes a month or longer. If you are getting chemotherapy as well, radiation treatments are usually delayed until chemotherapy is done. Some treatments after surgery, like hormone therapy or HER2 targeted therapy, can be given at the same time as radiation.

Types and schedules of external beam radiation for breast cancer

Whole breast radiation

Radiation to the entire affected breast is called whole breast radiation.

• The standard schedule for getting whole breast radiation is 5 days a week (Monday through Friday) for about 6 to 7 weeks.
• Another option is hypofractionated radiation therapy where the radiation is also given to the whole breast, but in larger daily doses (Monday through Friday) using fewer treatments (typically for only 3 to 4 weeks). For women who have had breast-conserving surgery (BCS) and whose cancer has not 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 longer periods of time. It might also lead to fewer short-term side effects.

Accelerated partial breast irradiation

After whole breast radiation or even after surgery alone, most breast cancers tend to come back very close to the area where the tumor was removed (tumor bed). For this reason, some doctors are using accelerated partial breast irradiation (APBI) in selected women to give larger doses over a shorter time to only one part of the breast (the tumor bed) compared to the entire breast (whole breast radiation). Since more research is needed to know if these newer methods will have the same long-term results as standard radiation, not all doctors use them. There are several different types of accelerated partial breast irradiation:

• Intraoperative radiation therapy (IORT): In this approach, a single large dose of radiation is given to the area where the tumor was removed (tumor bed) 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 (3D-CRT): In this technique, the radiation is given with special machines so that it is better aimed at the tumor bed. This spares more of the surrounding normal breast tissue. Treatments are given twice a day for 5 days or daily for 2 weeks.
• Intensity-modulated radiotherapy (IMRT): IMRT is like 3D-CRT, but it also changes the strength of some of the beams in certain areas. This gets stronger doses to certain parts of the tumor bed and helps lessen damage to nearby normal body tissues.
• Brachytherapy: See brachytherapy below.

Women who are interested in these approaches may want to ask their doctor about taking part in clinical trials of accelerated partial breast irradiation.

Chest wall radiation

If you had a mastectomy and none of the lymph nodes had cancer, radiation will be given to the entire chest wall, the mastectomy scar, and the areas of any surgical drains. It is typically given every day, 5 days a week, for 6 weeks.

Lymph node radiation

Whether or not you have had BCS or a mastectomy, if cancer was found in the lymph nodes under the arm (axillary lymph nodes), this area may be given radiation. In certain cases, the lymph nodes above the collarbone (supraclavicular lymph nodes) and behind the breastbone in the center of the chest (internal mammary lymph nodes) will also get radiation along with the underarm nodes. It is typically given daily 5 days a week for 6 weeks at the same time as the radiation to the breast or chest wall is given.

Possible side effects of external beam radiation

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

• Swelling in the breast
• Skin changes in the treated area similar to a sunburn (redness, skin peeling, darkening of the skin)
• Fatigue

Your health care team may advise you to avoid exposing the treated skin to the sun because it could 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 the skin to become firmer or swollen.
• Radiation may affect your options for breast reconstruction later on. It can also raise the risk of problems with appearance and healing if it’s given after reconstruction, especially tissue flap procedures.
• Women who have had breast radiation may not be able to breastfeed from the radiated breast.
• 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 might 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. Modern radiation therapy equipment focuses the radiation beams better than older machines, so these problems are rare today.
• A very rare complication of radiation to the breast is the development of another cancer called an angiosarcoma.

Brachytherapy

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 removed (tumor bed).

For certain women who had breast-conserving surgery (BCS), brachytherapy can 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

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 there until treatment is complete. There are several different devices available, most of which require surgical training for proper placement. They all go into the breast as a small catheter (tube). The end of the device inside the breast is then expanded like a balloon 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 in an outpatient setting. After the last treatment, the device is deflated and removed.

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.

Early studies of intracavitary brachytherapy as the only radiation after BCS have had promising results as far as having at least equal cancer control compared with standard whole breast radiation, but may have more complications including poor cosmetic results. Studies of this treatment are being done and more follow-up is needed.   

Possible side effects of intracavitary brachytherapy

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

• Redness and/or bruising at the treatment site
• Breast pain
• Infection
• Damage to fatty tissue in the breast
• Weakness and fracture of the ribs in rare cases
• Fluid collecting in the breast (seroma)