Some women with breast cancer need radiation therapy in addition to other treatments. Radiation therapy uses high-energy rays or particles to destroy cancer cells.

When is radiation therapy used for breast cancer?

There are several reasons you might get radiation therapy as part of your breast cancer treatment. This will depend on the stage of your cancer and other factors.

After breast-conserving surgery, to help lower the chance the cancer will come back in the same breast or nearby lymph nodes.

After a mastectomy, especially if:

Cancer is in the lymph nodes or the cancer is larger than 5 cm (about 2 inches).
Cancer cells are found in certain surgical margins, such as the skin or muscle. Surgical margins are the edges of tissue surrounding a tumor.

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

There are 2 main types of radiation therapy used to treat breast cancer:

External beam radiation therapy (EBRT)
Brachytherapy

External beam radiation therapy (EBRT)

External beam radiation therapy (EBRT) is the most common type of radiation used to treat breast cancer. For this type of treatment, a machine outside your body directs radiation to the area where the cancer was.

Which areas are treated with radiation?

You might need one or more areas treated. This will depend on the type of surgery you had and whether the cancer spread to nearby lymph nodes.

After breast-conserving surgery

Whole-breast radiation: After breast-conserving surgery, radiation is usually given to the entire breast.

An extra boost dose may be given to the area where the cancer was removed (the tumor bed). This is done especially if there is a higher risk of the cancer coming back.
The boost can be given during or after whole-breast radiation.

Accelerated partial breast irradiation (APBI): Radiation can also be given just to the lumpectomy cavity alone. This may be done for women who are over 40 years old and who have a breast tumor smaller than 2 cm with no cancer in the lymph nodes.

If lymph nodes are involved

Radiation may also be given to nearby lymph node areas. This includes:

Under the arm (axillary lymph nodes)
Above the collarbone (supraclavicular lymph nodes)
Near the breastbone (internal mammary lymph nodes)

When does radiation therapy start?

Radiation therapy usually starts after the surgical area has healed. This healing takes about a month, sometimes longer.

If you are also getting chemotherapy, you will probably wait to start radiation until you finish. Other treatments, such as hormone therapy and HER2-targeted therapy, are sometimes given at the same time as radiation.

Types of EBRT used for breast cancer

Possible side effects of EBRT

Short-term side effects

The main short-term side effects of EBRT to the breast are:

Swelling in the breast, which could cause pain and itching
Sunburn-like skin changes in the treated area such as redness, skin peeling, or skin darkening
Fatigue (extreme tiredness)

Your healthcare team may tell you to avoid exposing the treated skin to the sun, because this 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.

Late or long-term side effects

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

Possible changes to the breast:

The breast may become smaller.
The skin may feel firm or swollen.
You might not be able to breastfeed from the treated breast.
If you have radiation after reconstruction, it might affect how the breast heals and how it looks. This is especially true for tissue flap procedures.

Nerve damage and swelling:

Radiation to the lymph nodes under your arm might cause pain and swelling in the arm or chest. This is called lymphedema.

Rare side effects:

In rare cases, radiation therapy may weaken the ribs. This could lead to a fracture.
Very rarely, some of the nerves to the arm can be damaged when the lymph node regions are treated. This is called brachial plexopathy. It can lead to numbness, pain, and weakness in the shoulder, arm, and hand.
In the past, parts of the lungs and heart were more likely to get some radiation. This led to irritation and sometimes long-term damage of these organs in some people. Modern equipment is better at focusing the radiation beams, so these problems are rare today.
Developing another cancer called an angiosarcoma is a very rare complication of radiation to the breast.

Brachytherapy

Brachytherapy is another way to deliver radiation therapy after breast-conserving surgery. You might also hear this called internal radiation.

Instead of aiming radiation beams from outside your body, a device with radioactive seeds or pellets is placed into the breast tissue. It is placed in the area where the cancer was removed. It stays there for a short time.

For certain women who had breast-conserving surgery, brachytherapy can be used by itself instead of radiation to the whole breast. It is used as a form of accelerated partial breast irradiation.

Tumor size, location, and other factors may limit who can get brachytherapy.

Types of brachytherapy used for breast cancer

Brachytherapy after breast-conserving surgery is usually given in one of two ways.

Intracavitary brachytherapy: A balloon-tipped catheter is put into the surgical cavity, and radioactive pellets are delivered through it. It is done on an outpatient basis, then the device is removed. This is the more common method.
Interstitial brachytherapy: Multiple catheters are placed around the surgical area.

Both methods may cause side effects. These can include redness, bruising, breast pain, infection, fatty tissue damage, and fluid buildup. Brachytherapy can also cause rib fracture, but this is rare.

Radiation for Breast Cancer