Radiation Therapy

Written by Jamie DePolo | Reviewed by 2 medical advisers

Radiation therapy (radiotherapy) is a treatment that uses high-energy radiation to kill cancer cells and shrink tumors.

The radiation treatment procedure is painless, but it may cause some skin discomfort over time. When treating early-stage breast cancer, radiation therapy is often given after surgery. Surgery is done to remove the cancer, and radiation is done to destroy any cancer cells that may remain after surgery. This helps lower the risk of the cancer coming back (recurrence).

Radiation therapy also can be used to treat:

  • breast cancer that can’t be removed with surgery, which doctors call unresectable
  • metastatic breast cancer, which is breast cancer that has spread to parts of the body away from the breast, such as the bones, lungs, brain, or liver

How does radiation therapy work?

Radiation therapy uses special high-energy X-rays or particles to damage a cancer cell’s DNA. When a cancer cell’s DNA is damaged, it can’t divide successfully and it dies.

Radiation therapy damages both healthy cells and cancer cells in the treatment area. Still, radiation affects cancer cells more than normal cells. Cancer cells grow and divide faster than healthy cells and also are less organized. Because of this, it's harder for cancer cells to repair the damage done by radiation. So cancer cells are more easily destroyed by radiation, while healthy cells are better able to repair themselves and survive the treatment.

The treatment area may include the breast area, the lymph nodes, or another part of the body if the cancer has spread.

Radiation treatments are carefully planned to make sure you receive the greatest benefits and the fewest side effects possible. 

Types of radiation therapy

There are two main types of radiation therapy used to treat breast cancer:

External Beam Radiation

External beam radiation is given by a large machine called a linear accelerator. The machine aims a beam of radiation at the treatment area.

Brachytherapy or Internal Radiation

Internal radiation, called brachytherapy by doctors, uses a radioactive substance sealed in seeds or tiny tubes that are placed inside your body directly into the cancer or the place where the cancer was.

Intraoperative Radiation Therapy

Another type of radiation therapy, called intraoperative radiation therapy, is a type of partial-breast radiation. With intraoperative radiation therapy, the entire course of radiation is delivered at one time during breast cancer surgery.

A newer type of radiation therapy, called proton therapy or proton beam 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. 

When is radiation therapy used?

Radiation therapy can be used to treat all stages of breast cancer.

Pregnant women should not have radiation therapy because it can harm the unborn baby.

Radiation therapy after lumpectomy

Radiation therapy is recommended for most people who have lumpectomy to remove breast cancer. Lumpectomy is sometimes called breast-conserving surgery. The goal of radiation after lumpectomy is to destroy any individual cancer cells that may have been left in the breast after the tumor was removed. This reduces the risk of the cancer coming back (recurrence) and the risk of passing away from breast cancer.

Here’s a good analogy for understanding the role of radiation therapy after surgery: “If you drop a glass on the kitchen floor, you must first sweep up all of the big pieces of glass and throw them away — you can think of breast surgery in this way,” says Marisa Weiss, M.D., founder and chief medical officer of Breastcancer.org and director of breast radiation oncology at Lankenau Medical Center. “Radiation therapy is like vacuuming the area after you sweep, getting into the corners and under the furniture, to get rid of any tiny shards of glass that might be left behind.”

Radiation therapy after mastectomy

Radiation therapy may be recommended after mastectomy to destroy any cancer cells that may be left behind after the surgery. During mastectomy, it's difficult for surgeons to take out every cell of breast tissue.

Your doctor will look at your pathology report and calculate your risk of breast cancer recurrence based on a number of factors, including:

  • the number of lymph nodes involved
  • the size of the cancer
  • if cancer is at any of the edges of the surgery (positive margins)

If you have a high risk of recurrence, your doctor may recommend radiation after mastectomy to the area where the breast tissue used to be and sometimes to the nearby lymph node areas.

Radiation therapy for breast cancer is not an option if:

  • you have a connective tissue disease, such as scleroderma, which makes you extra-sensitive to the side effects of radiation
  • you are pregnant
  • you can’t commit to the daily schedule of radiation therapy, or distance makes it impossible

Can radiation therapy be repeated to the same area again?

Full-dose radiation is usually given only once to a particular part of the body. Your normal tissues can only tolerate a limited amount of radiation. Still, research has shown that repeat radiation with full doses to the same area may be possible in some situations.

If you are going to have radiation again in the same area, your radiation oncologist knows how to pick the right dose of radiation to accomplish two things:

  • reach the maximum therapeutic dose — the amount that's likely to destroy cancer cells
  • avoid or minimize side effects to the normal tissue

If cancer returns to the same area in the breast, you may or may not be able to receive a limited amount of additional radiation treatment in that same area. Your doctor will know what the limits are, and together you can decide if this is a good treatment option for you.

It's important to note that this information refers to treating the same part of the body a second time. If cancer occurs in another part of your body (including the other breast), a full dose of radiation can be used.

Radiation therapy timing and breast reconstruction

The timing of radiation treatment in your overall breast cancer treatment plan depends on your individual situation and the characteristics of the breast cancer.

In many cases, radiation therapy is given after surgery. If chemotherapy is planned after surgery, radiation usually follows chemotherapy.

If you’re having mastectomy and have decided to have breast reconstruction, it’s important to know that radiation can cause a reconstructed breast to lose volume and change color, texture, and appearance.

In particular, radiation therapy is known to cause complications with implant reconstruction. Research also suggests that a reconstructed breast may interfere with radiation therapy reaching the area affected by cancer, though this can vary on a case-by-case basis.

For these reasons, some surgeons advise waiting until after radiation and other treatments, such as chemotherapy, are completed before breast reconstruction surgery is done.

Other surgeons may recommend a more staged approach, which places a tissue expander after mastectomy to preserve the shape of the breast during radiation treatments. Once radiation is completed and the tissues have recovered, the expander that was used to maintain the shape of the breast is removed and replaced with tissue from another part of the body or a breast implant.

Radiation therapy side effects

The side effects of radiation therapy depend on the type of radiation therapy you’re having. In general, the side effects tend to develop as treatment goes on and may be more troubling toward the end of treatment. Overall, the most common side effects are redness, swelling, and skin peeling in the area being treated. Learn more about radiation side effects

Radiation for metastatic breast cancer

Sometimes breast cancer spreads to other parts of the body. When this happens, the breast cancer is called metastatic or stage IV.

If you’ve been diagnosed with metastatic breast cancer and are having symptoms, your doctor may recommend radiation therapy to:

  • ease pain
  • lower the risk of a cancer-weakened bone breaking
  • decrease bleeding open a blocked airway to improve breathing
  • reduce pressure on a pinched spinal cord or nerve that might be causing pain, numbness, or weakness
  • treat cancer that has spread to the brain

The radiation dose and schedule to treat metastatic breast cancer depends on a number of factors, including:

  • the level of pain or amount of function lost
  • the size of the cancer
  • the location of the cancer the amount of previous radiation you’ve had
  • the schedule for any other treatments

Staying on track with 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. In the past, it was given every day, 5 days a week, for 5 to 7 weeks. Accelerated, also called hypofractionated, radiation therapy schedules deliver about the same total dose of radiation over a shorter schedule — usually 3 to 4 weeks, which can be more convenient. Partial breast radiation (radiation treatment just to the area of the breast where the cancer was) can be completed in 1 to 3 weeks. Also, 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 and get back on schedule as soon as possible.
  • 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.

Vitamins to avoid during radiation therapy

Your radiation oncologist may tell you to avoid taking certain antioxidant vitamin supplements, such as vitamins C, A, D, and E, while you're having radiation therapy. These vitamins might interfere with radiation's ability to destroy cancer cells. This is because radiation works in part by creating free radicals — highly energized molecules that damage cancer cells. Free radicals in the environment can damage all cells, but in the case of radiation treatment they are focused on the cancer cells. Antioxidants help keep free radicals from forming or neutralize them if they do form.

Because of the potential conflict between the goal of radiation therapy (to make free radicals) and the goal of antioxidants (to neutralize free radicals), it makes sense to stop taking any antioxidant supplements during radiation therapy. When radiation is finished, you can resume taking your supplements.

Throughout your treatment, do your best to eat a well-balanced diet that contains all of the vitamins you need. Vitamins that come naturally from food are unlikely to interfere with treatment.

Radiation therapy and sun exposure

During radiation treatment, it’s best to keep the treated area completely out of the sun. This can be especially difficult if you’re having radiation therapy in areas or seasons with warmer weather. To help avoid sun exposure:

  • Wear clothing or a bathing suit with a high neckline, or wear a rash guard top.
  • Try to keep the area covered whenever you go outside. An oversized cotton shirt works well and allows air to circulate around the treated area.
  • Avoid chlorine, which is very drying and can make any skin reactions you’re having worse. Chlorine is used to disinfect most pools and hot tubs.
  • If you do want to swim in a pool, you might want to spread petroleum jelly on the treated area to keep the chlorine away from your skin.

After your radiation treatment is completed, the treated skin may be more sensitive to the sun than it was in the past, so you might need to take extra protective steps when you go out in the sun:

  • Use a sunblock rated 30 SPF or higher on the area that was treated.
  • Apply the sunblock 30 minutes before you go out in the sun.
  • Reapply the sunblock every few hours, as well as when you get out of the water.  


References Arthur DW, et al. JAMA Oncol. Nov. 21, 2019. Available at https://pubmed.ncbi.nlm.nih.gov/31750868/ — Last updated on November 11, 2022 at 3:08 PM

This information is provided by Breastcancer.org.

Posted in: In Treatment, Medical/Science, Treatment