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Updated September 27, 2010

Radiation treatment is a type of local therapy for breast cancer. The goal of radiation is to treat any cancer that remains in the area where the breast cancer was found. It helps protect you from the breast cancer coming back in the same place (local recurrence). When radiation is given after surgery as part of the primary treatment, it is called adjuvant therapy.

Radiation treatment is very effective against cancer in the specific area it is directed, but it will not treat cancer in other areas of the body. Because it is a local treatment, the side effects of radiation are related to the area where the treatment is given. It is unlikely to cause side effects elsewhere. Except for the time you are actively receiving radiation treatment in the cancer center, you are not “radioactive” and do not need to worry about exposing family members to radiation.

How Radiation Works

Radiation focuses the power of high-energy x-rays on areas where cancer cells may remain after breast cancer surgery, such as the breast tissue left after you have surgery on the breast and lymph nodes.

The standard treatment is external beam radiation therapy to the whole breast, which uses a machine called a linear accelerator to direct the x-rays into the breast from outside the body.

The sites for radiation treatment vary and depend on where the cancer was found. You may receive radiation to part of your breast, your whole breast, the chest wall, the area above your collarbone or under your arm.

How Do I Know If I Need Radiation?

At some point after your diagnosis, you will meet with a radiation oncologist. These doctors specialize in treating cancer with radiation.

Your doctor will talk with you about your medical history, other illnesses and your diagnosis of breast cancer. Then, with this information, the doctor can talk with you about the role of radiation in your treatment plan.

If you have lumpectomy (breast conservation surgery), you probably will have radiation treatment. If you have a mastectomy, you may not need radiation. To decide whether you need radiation after mastectomy, your doctor will look at the size of the tumor. The doctor will also check to see if cancer traveled to other tissues such as the lymph nodes, skin or muscle below your breast.

What Happens at Treatment?

Radiation can be given in different ways. Usually, you will receive it from outside of your body by an external beam, but it can also be given from inside the body.

Radiation treatment must be very precise. To find the right places to give radiation, your doctor will give you a CAT or CT scan. This special x-ray takes pictures of the inside of your breast from many different angles. Your radiation oncologist will then give you tiny tattoos to make sure the exact same spot is always radiated. They will be about the size of the top of a pin. Several days to a week later, you will begin treatments.

How long radiation treatment takes depends on the kind of treatment you receive. The two types of radiation for breast cancer are whole breast radiation and partial breast radiation.

Types of Radiation

There are two different types of radiation treatment for breast cancer.

Whole breast radiation

The standard treatment is whole breast radiation, given daily by external beam. It lasts for five to seven weeks. Each treatment takes about 15 minutes. The treatment to the entire breast lasts for about five weeks. After that, the remaining weeks have a boost, or extra treatment, to the tumor area. Accelerated external beam radiation, a newer treatment, gives whole breast radiation over three to four weeks.

Partial breast radiation

Partial breast radiation treats only the area where the tumor was found. It can be delivered through an external beam or internally through brachytherapy. In this procedure, a surgeon places a tiny balloon or hollow, flexible tubes called catheters in the tumor cavity. You then receive radiation twice a day for a week, with each treatment taking up to half an hour. When you complete treatment, the surgeon removes the catheters or balloon.

Doctors are still studying the effectiveness and side effects of this radiation approach. If you want this treatment, explore the risks and benefits with your doctor.

Side Effects

Radiation itself is not painful but has some side effects.


You may feel tired, so plan time to rest. Radiation treatments and their effects build up in your body over time, so as your treatments go on, your fatigue may increase. Expect to feel more tired in the last few weeks of treatment, and give yourself the chance to nap and rest.

Skin Reactions

The skin on or near the radiated area may become dry, sore, red, blistered or scaly. Ask your radiation nurse and radiation oncologist about how to keep your skin moist and comfortable.

Other Side Effects

External radiation also puts you at higher risk for developing some other conditions. Talk to your radiation oncologist about the risk of lymphedema.

Learn more about the people who helped us write this page in the Guide for the Newly Diagnosed.