External Beam Radiation
External beam radiation is the most common type of radiation therapy used to treat breast cancer. A large machine called a linear accelerator aims a beam of high-energy X-ray radiation at either the whole breast (whole-breast radiation) or just the area of the breast affected by the cancer (partial-breast radiation).
External whole-breast radiation schedule: Accelerated or traditional
For many years, external radiation was given on an outpatient basis, usually for five days a week over five to seven weeks. But a five- to seven-week nearly daily commitment is difficult for many people, especially if they live far away from a treatment center.
So doctors developed a radiation therapy schedule that involves fewer treatments with higher doses of radiation at each treatment. This accelerated, or “hypofractionated,” radiation schedule puts about the same total dose of radiation into a three- to four-week schedule.
A Gray is the way radiation oncologists measure the dose of radiation therapy. If you were on a traditional, five-week treatment schedule, 45–50 Gray was the usual total amount given over five weeks (1.8 to 2 Gray at each of 25 treatments).
The preferred accelerated (hypofractionated) dose schedule is 40 Gray in 15 doses or 42.5 Gray in 16 doses. This is often followed by a radiation boost dose to the area where the breast cancer used to be.
Listen to the episode of The Breastcancer.org Podcast featuring Dr. Chirag Shah discussing accelerated, or hypofractionated, radiation therapy for breast cancer.
In 2017, the National Comprehensive Cancer Network (NCCN) updated its guidelines on whole-breast radiation to say that an accelerated schedule should be the standard of care. 1 In 2018, the American Society for Radiation Oncology (ASTRO) also updated its guidelines to say that an accelerated schedule should be the standard of care for whole-breast radiation therapy.
External accelerated partial-breast radiation
For certain women with early-stage breast cancer, doctors may consider external accelerated partial-breast radiation. This technique gives a larger dose of radiation over a shorter period of time — one to three weeks — to only the part of the breast where the cancer was, rather than the entire breast.
It’s important to know that external accelerated partial-breast radiation is not for everyone diagnosed with breast cancer. Both the NCCN and ASTRO guidelines on accelerated partial-breast radiation say that this technique may be offered to:
Women age 50 and older without a BRCA mutation who are diagnosed with hormone-receptor-positive breast cancer that is 2 centimeters or smaller in size. The cancer must have been removed with clear margins, meaning no cancer was found in the margins, and the margins must be 2 millimeters or larger. There can also be no cancer cells in the blood vessels or lymphatic system.
Women diagnosed with low- or intermediate-grade DCIS that is 2.5 centimeters or smaller in size that has been removed with clear margins that are 3 millimeters or larger.
External accelerated partial-breast radiation has mostly been studied in women so far and is not recommended for men diagnosed with breast cancer.
Radiation boost
No matter which radiation schedule (traditional or accelerated) you receive, your doctor may recommend a radiation boost dose toward the end of your treatment schedule.
A radiation boost is a supplemental dose of radiation targeted directly at the area where the cancer was surgically removed. A separate planning session is usually required before the radiation boost can be given.
For people diagnosed with invasive breast cancer, ASTRO guidelines recommend a boost dose for:
cancers with positive margins after surgery (this means cancer cells came right up to the edge of the tissue removed)
people age 50 and younger
people age 51 to 70 diagnosed with high-grade breast cancer
ASTRO guidelines say a boost isn’t needed for:
people older than 70 diagnosed with hormone-receptor-positive, low- to intermediate-grade breast cancer with negative margins wider than 2 millimeters (this means no cancer cells were found in the rim of healthy tissue removed with the cancer)
For people diagnosed with DCIS, ASTRO guidelines recommend a boost dose for:
people age 50 and younger
people diagnosed with high-grade DCIS
DCIS with positive or close (less than 2 millimeters) margins
ASTRO guidelines say a boost isn’t needed for:
people older than 50 diagnosed with DCIS
DCIS that is small and low- to intermediate-grade
DCIS that has wide negative margins
Proton beam radiation therapy
A newer type of radiation therapy, called proton therapy, uses particles called protons rather than X-rays to treat cancer. Proton therapy for breast cancer is not the standard of care, is still being studied, and is not available at all treatment facilities.
Stereotactic radiation therapy
Stereotactic radiation therapy uses special equipment to deliver a high radiation dose per treatment to a small, well-defined area using several precisely focused radiation beams or arcs.
It’s commonly used to treat conditions in the brain and spine, including cancer. It’s also used to treat cancer in the lungs, liver, and prostate.
In breast cancer, stereotactic radiation may be used to treat spots of metastatic disease in the brain, spine, or other locations, such as the bones, lungs, or liver. The entire dose of radiation is often given in one to five treatments.
Stereotactic radiation therapy is also called:
stereotactic external beam radiation therapy
stereotaxic radiation therapy
stereotactic body radiotherapy
stereotactic radiosurgery
stereotactic ablative radiotherapy
You may also hear stereotactic radiation therapy called by a brand name, including CyberKnife or Gamma Knife.
While the words “surgery” and “knife” are in some of the names for stereotactic radiation therapy, it is not surgery because there is no incision.
The planning and treatment process for stereotactic radiation therapy is similar to regular external beam radiation. When you receive stereotactic radiation therapy, your treatment team will use immobilization devices.
In many cases, the side effects of stereotactic radiation therapy are milder than traditional external beam radiation therapy and usually get better a few weeks after treatment, though there can be some long-term side effects, but they depend on the area receiving treatment. Because stereotactic radiation therapy for breast cancer is often given to the brain or spine, common side effects are:
hair loss and skin irritation at the treatment site
scalp tingling or irritation
When stereotactic radiation therapy is used to treat metastatic lesions in the brain, it may cause swelling at or near the treatment site. Your doctor may prescribe anti-inflammatory medicines, such as steroids, to prevent swelling or treat any symptoms that you have.
External radiation planning and treatment: What to expect
External radiation treatments require careful planning to make sure the treatment area is mapped out as accurately as possible so that your treatment goes smoothly.
Here’s what you can generally expect from the planning session through your daily treatment routine.
Your first radiation therapy session is called a simulation. It is a planning and practice session, and you receive no radiation.
During the simulation session, your radiation oncology team maps out the area of the breast that needs treatment using imaging such as a CT scan, MRI, or X-ray.
Because it is so important to position the angles of radiation accurately, the simulation session can last up to an hour.
During the simulation session, your doctor:
explains the pros and cons of radiation, the planning and treatment process, and answer any questions or concerns you may have
reviews the consent form and has you sign it
introduces you to the treatment team
precisely identifies the area where you are going to receive radiation
Positioning is extremely important in radiation therapy. Your body is positioned carefully so you get the best radiation treatment possible with the greatest benefits and the least side effects. You may lie on your back (supine) or lie face down (prone). You are in the same position during every treatment, and you have to remain still. To stabilize your position, you are probably going to have to lie in a special immobilization device on the treatment table. Unfortunately, no padding can be used on the treatment table or positioning devices because anything soft would make your treatment position less precise.
There are different kinds of immobilization devices. Some look like a cradle; others look like a foam box that is shaped to your form. You are not trapped or closed in. You may be asked to lie down in a custom-shaped mold that just touches your back and sides, or your treatment center may use a breast board that places your head, arm, and hand in a fixed position. If you have left-sided breast cancer, you may receive special breathing instructions to help protect your heart during radiation treatment.
Pictures are taken of the treatment area. The images are sent to the radiation planning computer, which helps set up the treatment fields (areas that determine what parts of your body are going to receive treatment and what parts should be avoided). Once the treatment fields are set, the team places marks with small tattoos that are usually no bigger than the head of a pin or a freckle. The tattoo is a guide to help the technician line up the radiation treatment fields the same way each time you receive treatment. Tattoos are preferred because markers or pens are less precise and can fade or wash off.
A second planning session usually is needed to confirm the treatment and your positioning. Special X-rays are taken of each treatment field to make sure they are all set up correctly, and additional markings may be made to better define the confirmed treatment fields.
Here's what to expect during your visit to the radiation treatment center:
Your doctor is likely to tell you to not wear deodorant, antiperspirant, lotion, powder, perfume, or oils to your appointment. They can interfere with the radiation treatment.
You change into a hospital gown or robe when you arrive at the treatment center. You also need to remove any jewelry that might get in the way of the treatment.
A radiation therapist takes you to a treatment room where you are placed in your treatment position. For breast radiation, you lie on your back or your stomach with the arm on the treatment side raised above your head. An immobilization device is used to secure your position and make you more comfortable.
The technician carefully lines up the linear accelerator to treat the first treatment field. After the machine is positioned, the technician leaves the room. The technician can see you through a window or on a television screen and can hear through an intercom at all times.
The technician turns on the machine to deliver the radiation dose. Since you cannot feel radiation, the only way you know when you are exposed is by the whirring or clicking sound of the machine. While the machine is running, you must remain completely still. It takes only between 30 seconds and a few minutes to deliver the radiation (depending on the type and dose of the radiation being used).
The technician comes back into the room to find the position for the next field to be treated. If you are receiving radiation to lymph nodes, you may have extra fields during the session.
Each week, you have special X-rays taken of the treatment field. These are called port films. Your doctor uses these to double-check that the radiation is precisely hitting the correct areas of your body. Because the tattoos or marks on your skin can shift with your skin, it's important to have one more way to make sure that the treatment is precise.
Staying on track with external radiation treatments
The benefits of radiation therapy strongly depend on getting the full recommended dose without significant breaks, because:
The full dose of radiation is needed to get rid of any cancer cells remaining after surgery.
Radiation therapy is most effective when given continuously on schedule.
By seeing your doctor regularly during and after treatment, you can best deal with any side effects.
Why you might have problems sticking to your radiation therapy plan:
The treatment schedule may conflict with job demands, family needs, or the distance you live from the treatment facility. This may cause you to miss or postpone appointments, even if you’re on an accelerated schedule.
Skin irritation from radiation can cause soreness, peeling, and sometimes blisters. If you've also had lymph-node surgery, radiation treatment may worsen breast or underarm pain or discomfort. If you have these side effects, you might feel like stopping radiation.
Ways to overcome problems and stay on track with radiation treatment:
Talk with staff members at your radiation treatment center about your scheduling needs. They will try to work out an appointment schedule that's as convenient as possible for you.
It’s best to continue your treatment without interruption. But an occasional short-term break of a day or two off from treatment is unlikely to reduce the effectiveness of radiation therapy. So if you need to take a short break, let your doctor know.
If you must miss a session, it will be added on to the end of your treatment schedule. Discuss your updated treatment plan with your radiation treatment team.
Learn about radiation side effects and how to manage them.
If your skin is uncomfortably raw, ask your doctor about a skin care program that may involve prescription medicines. Very occasionally, it may be necessary to take a brief break to allow the skin to recover. Talk to your doctor about how much time you can take off and how to get back on schedule as quickly and comfortably as possible.
Salerno, KE. NCCN Radiation Guideline Update. JNCCN. May, 2017. Available at: https://doi.org/10.6004/jnccn.2017.0072
Shah C, et al. American Brachytherapy Society Consensus Statement on accelerated partial-breast radiation. Brachytherapy. 2017. Available at: https://pubmed.ncbi.nlm.nih.gov/29074088/
— Last updated on December 12, 2024 at 9:25 PM