Radiation therapy for breast cancer

Radiation is sometimes called local therapy because it is delivered locally to a specific area of the body. (Systemic therapies, such as chemotherapy and other medicines, spread throughout the whole body.)

Radiation therapy can be very effective in lowering the risk of early- and advanced-stage cancer coming back (recurrence). These breast cancers include DCIS, early-stage invasive breast cancer, and lymph node-positive disease.

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.”

Radiation therapy is usually given after cancer-removal surgery. In early-stage breast cancer, radiation may be given to part of your breast or your whole breast after lumpectomy, which is also called breast-conserving surgery. 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. 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, such as the bones or the brain.

While radiation therapy can kill cancer cells or slow their ability to grow, radiation can also damage healthy cells. Side effects can vary depending on the type and amount of radiation you have, but they often include redness and peeling of the skin, breast swelling, and fatigue.

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

Types of radiation therapy for breast cancer

The type of radiation therapy you receive will depend on many different factors, such as the features of the breast cancer, its stage, and your age and overall health. Your radiation oncologist, a doctor who specializes in treating cancer with radiation, can help you make an informed choice about radiation therapy.

One key decision is whether you need whole or partial breast radiation therapy, for those women who have had a lumpectomy. Whole breast radiation therapy treats the entire breast, and possibly the chest wall and lymph nodes, while partial breast radiation focuses on the part of the breast where the cancer was found. If all of the breast tissue was removed (mastectomy), radiation therapy may be used to treat the chest wall and lymph nodes.

For whole and partial breast radiation therapy, as well as radiation used to treat the chest area/underarm area after mastectomy, external beam radiation therapy is the most common approach. Techniques can include:

• 3D conformal radiation (3D-CRT): This procedure uses 3D imaging to direct photon beams, or x-rays, toward the whole breast or just part of the breast. If it’s being used for partial breast radiation, the team can aim the radiation at the area from which the cancer was removed, also called the tumor bed. This helps to limit the impact of radiation on the surrounding healthy breast tissue.
• Intensity-modulated radiation therapy (IMRT): IMRT is similar to 3D-CRT, but it can change (or modulate) the strength of the x-ray beams to certain areas. This focuses more intense doses of radiation to parts of the tumor bed, lessening the impact on healthy tissue. Although IMRT is more commonly used for partial breast radiation, it sometimes may be used to treat the whole breast.
• Proton therapy: Instead of using traditional x-rays, this type of radiation therapy delivers a beam of proton particles directly to the area (or areas) of concern. It is more expensive than traditional radiation and is only available at selected cancer centers. Researchers are investigating the use of proton therapy for breast cancer, including whether it causes fewer side effects to the heart than traditional radiation. Although proton therapy is more commonly used for partial breast radiation, in some cases it may be used for whole breast radiation.

In metastatic breast cancer, these radiation techniques can be used to reduce symptoms caused by areas of cancer spread, such as in the bones, spine, brain, or lungs. Other techniques may include stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT). These use specialized equipment to position a person and deliver high doses of radiation precisely to tumors in other areas of the body. SRS is used to treat tumors in the brain, while SBRT is used to treat tumors in other parts of the body. The radiation is delivered over several days.

For partial breast radiation, the following techniques may also be used instead of the external beam radiation techniques mentioned above, depending on the features of the breast cancer and your individual situation:

• Brachytherapy, also called internal radiation: In this procedure, a surgeon places an applicator device or hollow, flexible tubes called catheters into the area where the cancer was. This placement may happen during lumpectomy surgery or a few weeks later. Small pellets or seeds containing radiation are inserted into the area through the applicator or catheters for a short time, and then removed. 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 applicator. Brachytherapy is less widely available than external beam radiation.
• Intraoperative radiation therapy (IORT): This procedure usually takes place during lumpectomy surgery. After doctors remove the tumor, one large dose of radiation is given directly to the surgical area before the incision is closed. In some instances, IORT is done later by reopening the lumpectomy incision to deliver the radiation. IORT is still being studied, is not available at many hospitals, and it is generally recommended that you participate in a clinical trial to receive IORT. Visit the IORT page to learn more.

Schedules for whole and partial breast radiation can vary. Traditionally, whole breast radiation treatment is given at an outpatient center five days a week for three to five weeks, although some people may need treatment for five to seven weeks. The shorter treatment is called hypofractionated whole breast radiation therapy, and it gives a larger dose over less time. For other people, shorter courses of partial radiation, also known as accelerated partial breast radiation, may be available, lasting about one to two weeks. Each radiation treatment takes about 15 minutes.

To learn more about timing and schedules, visit the radiation schedules for breast cancer treatment page.

Partial breast radiation for early-stage breast cancer and DCIS

In 2023, the American Society for Radiation Oncology (ASTRO) updated its guidelines on partial breast radiation in early-stage invasive breast cancer or ductal carcinoma in situ (DCIS).

Partial breast radiation for early-stage invasive breast cancer

For early-stage, invasive breast cancer, the ASTRO guidelines strongly recommend partial breast radiation as an alternative to whole breast radiation if all of the following are true:

• The breast cancer is grade 1 or 2 and estrogen-receptor positive.
• The tumor is two centimeters or smaller.
• You are 40 or older.

Partial breast cancer radiation may be an option if early-stage invasive breast cancer has one of the following features, but should be discussed in detail with your radiation oncologist:

• The breast cancer is grade 3, or
• The breast cancer is estrogen receptor-negative, or
• The tumor is larger than two centimeters but no larger than three centimeters.

If more than one of the above is present, the ASTRO guidelines say that partial breast radiation may not be appropriate due to the increased risk of recurrence. Whole breast radiation may be recommended instead.

The risk of recurrence in early-stage invasive breast cancer may be too high for partial breast radiation if any of the following are true:

• The cancer is HER2-positive but being treated with anti-HER2 treatment.
• There is lymphovascular invasion.
• The diagnosis is lobular carcinoma.

In this case, whole breast radiation may be recommended.

The guidelines strongly recommend against partial breast radiation in early-stage invasive breast cancer if any of the following are true:

• There are positive lymph nodes.
• There are positive surgical margins.
• You have tested positive for an inherited BRCA1/2 mutation.
• You are under age 40.

Partial breast radiation for DCIS

For DCIS, the ASTRO guidelines strongly recommend partial breast radiation as an alternative to whole breast radiation if all of the following are true:

• The grade of the DCIS is 1 or 2.
• The size of the DCIS is two centimeters or smaller.
• You are 40 or older.

In some cases, according to the guidelines, if DCIS is high-grade or larger than two centimeters but no larger than three centimeters, partial breast radiation may be recommended. If the cancer is both high-grade and between two and three centimeters, the risk of recurrence may be too high for partial breast radiation, so whole breast radiation may be recommended instead.

ASTRO guidelines strongly recommend against partial breast radiation if:

• The DCIS has positive surgical margins.
• You test positive for an inherited BRCA1/2 mutation.
• You are younger than 40.

Read the 2023 ASTRO guidelines on partial breast radiation in early-stage breast cancer or DCIS to learn more.

When is radiation therapy used to treat breast cancer?

Radiation therapy is given:

• After lumpectomy surgery, to destroy any cancer cells that might remain in the breast tissue after the cancer is removed
• After mastectomy if the cancer was over 5 centimeters across, was in the skin or muscle, or was in lymph nodes
• To treat metastatic breast cancer that has spread to other parts of the body, such as the brain or the bones

Before giving any form of external radiation after surgery, your care team usually will wait until the surgical site has healed, which can take a month or longer.

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. Although partial breast radiation is still being studied, there is evidence from research showing that, in selected women, accelerated partial breast radiation can be just as effective as whole breast radiation in lowering the risk of recurrence. Some emerging research also suggests that it may be safe for some patients with low recurrence risk to skip radiation after lumpectomy, based on an informed discussion with their radiation oncologist. 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. However, 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 the symptoms of cancer that has spread to other organs, such as the brain or bones. Radiation therapy can help with pain relief (with bone pain, for example), preventing or treating bone fractures, or treating lesions in the brain or liver.

In some situations, radiation therapy is not recommended. Radiation therapy is not safe for pregnant women at any time during pregnancy because it poses a risk to the developing baby. If you’ve already had radiation to the chest area, or if you have a connective tissue disease involving the skin, such as scleroderma, your care team might not recommend radiation therapy, or may refer you to a radiation center with more specific experience. Radiation therapy may also not be recommended if you have a pacemaker implanted in your heart. Talk with your healthcare team about your individual situation and whether or not radiation therapy is safe for you. If it’s not, other treatment options are available.

If your job, family obligations, or other life circumstances make it difficult to go to radiation treatments, it’s important to let your doctors know. Ask if adjustments can be made in the schedule, or if 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 time frame.

Timing of radiation therapy with other breast cancer treatments

Radiation therapy is one of many breast cancer treatment options. Other potential treatments can include chemotherapy, endocrine therapy, and targeted therapies. Some of these treatments can be given during the weeks you have radiation therapy, and others can’t.

According to the National Comprehensive Cancer Network (NCCN):

• If chemotherapy is recommended, it is typically completed before radiation therapy. The only chemotherapy regimen that can be given at the same time as radiation therapy is CMF, or cyclophosphamide (Cytoxan), methotrexate (Amethopterin, Folex, Mexate, Rheumatrex), and fluorouracil (5-FU). CMF is used to treat early-stage breast cancers. This is a not commonly used regimen.
• The chemotherapy capecitabine (Xeloda), used for metastatic breast cancers, is generally not given during radiation therapy. This is because it may make you more sensitive to radiation side effects. Experts don’t yet know how safe it is to treat someone with capecitabine and radiation at the same time in routine use. Capecitabine is usually given after radiation therapy ends. However, there are some rare instances in which capecitabine is used during radiation.
• Olaparib (Lynparza), a targeted therapy used to treat HER2-negative breast cancer in people who carry an inherited BRCA mutation, is not given during radiation therapy. This is because it may also make you more sensitive to the effects of radiation. Experts don’t
• Endocrine therapy for estrogen receptor-positive breast cancers can be taken during the weeks you receive radiation therapy. In some cases, a doctor may recommend waiting until after radiation to start endocrine therapy.
• Targeted therapy for HER2-positive breast cancer is generally safe to receive during the weeks you have radiation therapy, although some newer targeted therapies may be paused during radiation therapy.

Re-radiating the breast after a breast cancer recurrence

While recurrences in the same breast are rare after undergoing radiation therapy the first time, it is possible to have a same-breast recurrence.

If you’re planning treatment for a breast cancer recurrence in the same breast as your primary diagnosis, it may be possible for you to have radiation therapy again. According to the NCCN, you may be eligible to have radiation therapy to the same breast a second time if you:

• Had lumpectomy for your first diagnosis
• Had whole breast radiation

To treat the recurrence, you’d have a second lumpectomy before the new round of radiation therapy, is often partial breast radiation. It’s possible your care team will recommend proton therapy instead of traditional external beam radiation, because proton therapy can be aimed more directly at the area with cancer.

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 financial matters 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 external radiation therapy, you’ll have a planning session called a simulation. This session is designed to put you in a comfortable, safe position to receive radiation. 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 indicate where radiation should go and where it should not. Your team will position you on the treatment table and use imaging scans, such as a CT scan or MRI, to 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, some centers may place tattoos or marks on the skin to assist with positioning you correctly during the actual treatment. 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 areas are always radiated.

Getting radiation therapy tattoos can feel like a mosquito bite or a pinch. This feeling is temporary and will go away. In general, a person may receive 4 to 8 tattoos. While these tattoos are permanent, they are so small that they’re not usually visible to most people looking at you.

People have different feelings about getting radiation therapy tattoos. Some people aren’t bothered by the idea of receiving the tattoos. Over the long term, they find they no longer notice nor focus on the permanent markings. Some even see it as a positive reminder of their cancer journey. However, other people prefer not to have tattoos, whether for cultural, religious, or personal reasons, or because they are fearful of needles or concerned about the pinching sensation. They might not want to have a permanent visual reminder of their cancer. Some centers do offer tattoo-free options, so you can check with your healthcare team to see what is available.

Some centers can mark out the area to be treated with semi-permanent pen marks or stickers. It is important that these skin marks be kept for the duration of treatment to allow for accurate positioning each day. You will need to be careful when bathing and washing so as to not remove these marks.

Other centers offer an advanced technology called Surface Guided Radiation Therapy (SGRT). SGRT uses thousands of virtual tattoos to monitor your position during treatment and ensure that the radiation is delivered accurately to the right areas of the body. As a result, no marks need to be made on the skin. Centers that have this technology often offer both tattoo and mark-free treatment.

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

Radiation simulation for brachytherapy: If you’re having brachytherapy, you will not need tattoos or external markings. After the radiation delivery applicator device is implanted in the breast, you will lie on a table and have a CT scan that helps your radiation oncologist plan how to target the correct areas.

What to expect during radiation

Receiving external breast radiation is much like getting an x-ray. In general:

• The radiation therapist leads you to a treatment room and helps you onto a flat table.
• You lie on the table while your radiation therapist lines up your tattoos or other markers with the radiation machine.
• Your body is positioned to ensure the treatment is given exactly as planned.
• The radiation therapist then leaves the treatment area to begin treatment from the control room.

Each treatment takes about 15 minutes. You must stay still and as relaxed as possible during this time. The machine will not touch you, and the procedure itself is painless. You may hear noise from the machine or see the warning light — this is normal. The therapist may come into the room several times to reposition the machine and your body. You may be asked to hold your breath for brief periods using the deep inspiration breath hold technique.

The room has a camera so that the radiation therapist can see you. It also has an intercom, so you can tell the therapist right away if you have a problem. You will not be radioactive, and you will not expose others to radiation.

The radiation therapist will take an x-ray called a port film at different times during treatment. The port films help ensure you are being positioned correctly during your treatments. They are usually done at the beginning of treatment and then daily or weekly, depending on the technique being used for your radiation. The machine that delivers the treatment captures these port films while you are on the treatment machine.

If you’re having brachytherapy, or internal radiation, it can be done in a couple of different ways:

• Intracavitary radiation therapy is a form of brachytherapy where an applicator is inserted into the cavity, or space, from which the tumor was removed. The end of the device expands like a balloon and stays in place during treatment, and it’s connected to a small tube (or catheter) that extends outside the breast. Twice a day over about one to two weeks, a radiation oncologist places small radioactive seeds or pellets into the catheter. The seeds stay inside the body just long enough to give the prescribed dose of radiation. You will feel nothing during the procedure, which usually takes five to 10 minutes. After all treatments are complete, the applicator is removed. During insertion and removal of the applicator, your team can use a local injected anesthetic to numb the breast.
• Interstitial radiation therapy is a less common form of brachytherapy similar to intracavitary brachytherapy, but many catheters are used. The catheters are placed through the skin into the breast. The radioactive pellets are placed inside the tubes for short periods over several days and then removed.

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.

Radiation therapy to the left breast can have an impact on your heart health, although the deep inspiration breath hold (DIBH), or prone breast, technique can reduce some of the risk. Ask your healthcare team what they recommend as a heart health follow up plan to check for heart damage.

Visit the breast radiation side effects page for tips on managing these and other temporary changes.