Radiation therapy for breast cancer

Radiation therapy uses high-energy rays or particles to destroy cancer cells.

Radiation therapy is commonly used to treat breast cancer. Your healthcare team will use what they know about the cancer and about your health to plan the type and amount of radiation, and when and how it is given.

You may have radiation therapy to:

• destroy cancer cells left behind after surgery to reduce the risk that the cancer will come back (recur) (called adjuvant therapy)
• shrink a tumour before surgery (called neoadjuvant therapy)
• treat breast cancer that comes back in the area of a mastectomy
• relieve pain or control or prevent the symptoms of advanced breast cancer (called palliative therapy)

Doctors use external radiation therapy to treat breast cancer. During external radiation therapy, a machine directs radiation through the skin to the tumour and some of the tissue around it. Radiation therapy is usually given 5 days a week for 1 to 6 weeks. External radiation therapy is also called external beam radiation therapy.

You may be offered brachytherapy if you had early-stage breast cancer. Brachytherapy is a type of internal radiation therapy. A sealed container of a radioactive seeds, called an implant, gets placed right into the tumour or in the area where the tumour was removed. The radiation kills the cancer cells over time.

You may not be able to have radiation therapy if you have already had radiation therapy to the chest or breast or if you are pregnant. Doctors may not offer radiation therapy if you have lung problems, damaged heart muscles or a pacemaker, or certain connective tissue diseases (like lupus or scleroderma).

Radiation therapy is commonly given after breast-conserving surgery (BCS) to lower the risk that cancer will come back in the breast. External radiation therapy is directed at all of the breast including the skin and the muscles on the chest. You may also be offered radiation to the lymph nodes under the arm (called the axillary lymph nodes) because research shows that this may lower the risk that the breast cancer will come back and may improve survival.

After the radiation therapy to the breast is complete, you may get an extra dose, or boost, of radiation to the area from where the cancer was removed. You may get a boost if one of the following applies:

• cancer cells are found in the tissue removed along with the tumour (called positive surgical margins)
• the tumour is larger than 5 cm
• the cancer is high grade
• you are younger than 50

You may not need radiation therapy if all of the following apply:

• you are 70 or older
• the tumour is 2 cm or smaller
• the cancer has not spread to lymph nodes
• the cancer cells are hormone-receptor positive and you are taking hormone therapy

After a mastectomy, external radiation therapy may be directed to:

• the area where the breast was removed (including the chest wall and mastectomy scar)
• the areas where drains were placed after the surgery
• lymph nodes under the arm (called the axillary lymph nodes)
• lymph nodes in front of the shoulder near the collarbone
• lymph nodes beneath the breast bone in the middle of the chest.

You may have radiation therapy after a mastectomy if one of the following applies:

• the cancer has spread to lymph nodes
• the tumour is larger than 5 cm
• the tumour grew into the skin or muscles

A boost of radiation may also be given to the chest wall or mastectomy scar after the main radiation therapy treatment is complete.

Radiation therapy is not usually given after a mastectomy if all of the following apply:

• the tumour was smaller than 5 cm
• the cancer has not spread to lymph nodes
• cancer cells aren’t found in the tissue removed along with the tumour (called negative or clear margins)

If you need radiation therapy after surgery, it is usually not started until after your breast heals from surgery. This usually takes 3 to 4 weeks. It can take longer if you get an infection or have problems healing. Research shows that radiation therapy may be given up to 12 weeks after surgery.

If chemotherapy and radiation therapy are both part of your treatment plan, radiation therapy usually starts after chemotherapy is finished. This is because the side effects of some chemotherapy drugs given for breast cancer may be worse if you also have radiation therapy. Other treatments, like hormone therapy or targeted therapy, may be given at the same time as radiation therapy.

Some treatment centres have waiting lists, and it can take some time for radiation therapy to begin. Try not to worry if you have to wait. Researchers have found that waiting up to 7 months to start radiation therapy after surgery (and after chemotherapy has already been given) doesn’t increase the risk that the cancer will come back in the breast tissue (called a local recurrence).

During radiation therapy, your healthcare team protects healthy cells in the treatment area as much as possible. Side effects of radiation therapy will depend mainly on the size of the area being treated, the specific area or organs being treated, the total dose of radiation and the treatment schedule. Tell your healthcare team if you have side effects that you think are from radiation therapy. The sooner you tell them of any problems, the sooner they can suggest ways to help you deal with them.

Some common side effects of radiation therapy used for breast cancer are:

• fatigue
• skin problems
• changes to the size and shape of the breast
• changes to feeling in the breast
• breast pain
• lymphedema
• problems moving the shoulder
• inflammation of the lung caused by radiation therapy to the chest (called radiation pneumonitis)

Find out more about radiation therapy and side effects of radiation therapy. To make the decisions that are right for you, ask your healthcare team questions about radiation therapy.