Radiation therapy, also known as radiotherapy, directs high-energy x-rays to a specific part of the body to kill cancer cells. For early-stage breast cancer, there are two general types of radiation therapies: whole breast radiation and partial breast radiation. Radiation and other treatments focused on a certain part of the body are often called local therapy because they are “local” to one part of the body.

Radiation therapy can be very effective in lowering the risk of early- and advanced-stage cancer coming back. This includes diagnoses like DCIS, early-stage invasive breast cancer, lymph-node positive disease, and inflammatory breast cancer.  

We know that radiation therapy is very effective for reducing the risk of breast cancer recurrence. According to Neil Taunk, MD, MSCTS, “After surgery and radiation therapy, recurrences in the breast, chest, or lymph nodes after targeted radiation to those areas are quite uncommon. However, the rate of recurrence can vary based on characteristics such as the tumor type, surgery, lymph node involvement, and use of systemic therapy.”

In early-stage breast cancer, radiation may be given to part of your breast or your whole breast. After mastectomy or in lymph-node positive disease, treatment may also include radiation to the chest wall, the area above your collarbone, or under your arm. It’s usually given after surgery to remove the cancer. If chemotherapy and radiation therapy are recommended, chemotherapy is typically completed before radiation.

In metastatic breast cancer, radiation therapy can slow cancer growth or relieve pain from breast cancer that has spread to other parts of the body, like the bones or the brain.

While radiation therapy can kill cancer cells or slow their ability to grow, radiation can also damage healthy cells. Common side effects of radiation therapy can include redness and peeling of the skin, breast swelling, and fatigue. 

On this page, we’ll explain the different kinds of radiation therapy available for breast cancer treatment, when radiation is typically recommended, and what you can expect with treatment.

Types of radiation therapy for breast cancer

The two main types of radiation therapy for breast cancer are external beam radiation therapy (EBRT) and internal radiation, or brachytherapy.

• External beam radiation is the most common type of radiation therapy used to treat breast cancer. From outside the body, a large machine called a linear accelerator directs high-energy x-rays into the area affected by the cancer.
• External beam radiation therapy can be directed at the entire breast (whole breast radiation) or part of the breast (partial breast radiation).
• Partial breast radiation focuses mainly on the area where the cancer was first found.
• Partial breast radiation can also be given internally using a type of treatment called brachytherapy. In this procedure, a surgeon places a tiny balloon or hollow, flexible tubes called catheters in the area where the tumor was. In most cases, brachytherapy radiation is given on an outpatient basis, twice a day for a week. Each treatment may take up to half an hour. When you complete treatment, the surgeon removes the catheters or balloon. Brachytherapy is less available than external beam radiation.
• Another form of partial breast radiation is called intraoperative radiation therapy (IORT). This procedure takes place during lumpectomy surgery, or sometimes in a second procedure after lumpectomy. After doctors remove the tumor, one large dose of radiation is given to the surgical area before the incision is closed. IORT is still being studied and is not available at many hospitals. Visit the IORT page to learn more.

Schedules for whole and partial breast radiation can vary. Usually, whole breast radiation treatment is given at an outpatient center 5 days a week for 3 to 5 weeks, but shorter schedules may be an option in some cases. Each treatment takes about 15 minutes. Short courses of external beam partial radiation may also be available. To learn more about timing and schedules, visit the Radiation Schedules for Breast Cancer Treatment page.

When is radiation therapy used to treat breast cancer?

Radiation therapy is given

• after lumpectomy surgery to remove a breast tumor, to kill any cancer cells that might remain in the body after surgery
• after mastectomy if the cancer was over 5 centimeters across, was in the skin or muscle, or was in lymph nodes
• to treat areas of metastatic breast cancer spread to other parts of the body, such as the brain or the bones

After lumpectomy, almost everyone benefits from radiation therapy to some degree, so it’s almost always recommended. Research shows that lumpectomy plus whole breast radiation can greatly reduce the risk of recurrence when compared with lumpectomy alone. Some emerging research suggests that it may be safe for some groups with low recurrence risk, after an informed discussion with their radiation oncologist, to skip radiation after lumpectomy. It’s important to talk with your healthcare team about your risk of recurrence and the most effective plan for keeping your risk as low as it can be.

With a mastectomy, you may not need radiation. Your doctor may recommend radiation therapy to reduce the chance of the cancer coming back in your skin, the chest wall, or nearby lymph nodes if

• the primary tumor is larger than 5 centimeters across
• the cancer is in the lymph nodes under your arm
• the cancer has grown into the skin or chest wall muscle under the breast
• you have locally advanced or inflammatory breast cancer

In metastatic breast cancer, radiation therapy can be used to treat cancer that has spread to certain areas, such as the brain. Radiation therapy can help with pain relief (with bone pain, for example) and reducing the risk of cancer-related complications.

In some situations, radiation therapy is not recommended. Radiation therapy is not safe for pregnant women at any time during pregnancy because of the risk radiation poses to the developing baby. If you are pregnant and have been diagnosed with breast cancer, talk with your healthcare team about your treatment options.

If your job, family obligations, or other life situations make it difficult to come to radiation treatments, it’s important to let your doctors know. Ask if adjustments can be made in the schedule, or there are other options available to you. Your doctor may be able to offer a different schedule that allows a slightly higher dose of radiation in a shorter timeframe.

What to expect before radiation therapy treatment

If your doctor has recommended radiation therapy for you, here are some things you can expect as you prepare to start treatment.

Informed consent

You will likely be asked to sign an agreement between yourself and your healthcare team that grants them permission to treat you. This ensures that you’ve had a chance to ask questions and your doctor has given you all the radiation therapy information you need, including the risks and benefits of the treatment. This process is called informed consent. Informed consent protects your right to have regular communication with and information from your healthcare team.

Treatment planning

Before you start radiation therapy treatment, you and your healthcare team will decide on a treatment schedule. The typical schedule for standard whole breast radiation treatment is once a day, 5 days a week, for 3 to 5 weeks. Partial breast radiation may mean a shorter course of treatment in some cases. You can learn more about schedules on the Radiation Schedules for Breast Cancer Treatment page.

Treatment planning also means understanding costs and your health insurance coverage. In the Job and Financial Concerns section, you can learn about health insurance, work accommodations after a breast cancer diagnosis, and more. One way to cut costs, have access to new treatment methods, and potentially help others diagnosed with breast cancer in the future is to participate in a clinical trial. Visit the Clinical Trials page to learn more.  

Radiation simulation

Before you start receiving actual radiation treatments, you’ll have a planning session called a simulation. This is something like a treatment dress rehearsal. On that day, you’ll do everything you would on a normal treatment day, except receive the radiation. This allows the radiation oncologist and radiation therapists to get familiar with the treatment plan and make adjustments, if needed. Your team will position you on the treatment table and find the exact area on your body where the radiation will be targeted. You may be asked to hold your breath, put your arms over your head, or position your head a certain way. This helps you and your team identify how your body will be positioned for every treatment.

In some cases your team may recommend using a technique called deep inspiration breath hold (DIBH) to reduce the risk of radiation reaching the heart area. If this has been recommended for you, you will be coached on how to practice DIBH before and during the simulation session.

During simulation, your radiation team will determine where small tattoos — dots of permanent ink about the size of a small freckle — will be placed on your body. The tattoos help make sure the exact same area is always radiated. If more radiation is needed later, the tattoos ensure that doctors know you’ve had previous radiation there, because radiating the same area more than once is not usually recommended.

Many women say that getting the tattoos feels similar to a pin prick. In general, a person may receive 4 to 8 tattoos. While these tattoos are permanent, they are so small that they’re not usually very visible to most people looking at you.

Several days to a week after the simulation session, you will begin treatment.

What to expect after receiving radiation

Once you’ve started radiation therapy, you may begin to notice side effects such as skin redness and irritation (like a sunburn), breast swelling, and as treatment continues, fatigue.

Skin side effects often heal several weeks after you finish treatment. Changes to the color of your skin may take longer to heal, but your radiation oncologist will monitor your skin in the weeks after you complete treatment.

Visit the Breast Radiation Side Effects page for tips on managing these and other temporary changes.

Additional resources

Below, you can find more articles about radiation therapy for breast cancer, stories from others who’ve been there, and downloadable resources to support you as you make important decisions about your care.

Related pages

• Preparing for breast cancer treatment
• Getting a second opinion
• Breast reconstruction decisions
• Questions to ask your doctor

Related news & opinion

• How COVID-19 affects early-stage breast cancer treatment
• The Choice: When Is Chemotherapy the Right Treatment for Breast Cancer?
• Skin care and scarring after breast cancer surgery and radiation therapy

From the blog

• Taking Steps to Preserve Fertility
• What I wish I knew: have someone with you
• What to expect at a virtual appointment

 Free downloadable resources

• Guide to Understanding Treatment Decisions (PDF)
• Guide for the Newly Diagnosed (PDF)