Lying Face Down for Radiation Therapy to Treat Breast Cancer May Protect Healthy Tissue

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A study shows that lying face down (also called “prone”) to receive radiation therapy to the breast area reduces the amount of radiation that unintentionally reaches the heart and lungs.

The research was published in the Sept. 5, 2012 issue of the Journal of the American Medical Association. Read the preview of “Prone vs Supine Positioning for Breast Cancer Radiotherapy.”

Experts agree that radiation therapy improves the overall prognosis for many women diagnosed with early-stage breast cancer. Still, studies have found a link between radiation therapy and a higher risk of heart and lung problems. Because the heart is on the left side of the chest, it may be unintentionally be exposed to more radiation in women diagnosed with cancer in the left breast compared to women diagnosed with cancer in the right breast.

In this study, the researchers looked at 400 women diagnosed with early-stage breast cancer (stage 0 to stage IIA) from 2005 to 2008:

  • 200 women were diagnosed with cancer in the left breast
  • 200 women were diagnosed with cancer in the right breast

The women all were treated at New York University. They were about 56 years old and 80% of them were white. About 21% of the women were diagnosed with DCIS (stage 0).

To see if lying face down exposed less healthy tissue to radiation than lying face up, the researchers figured out how much heart and lung tissue would be in the radiation treatment field in each position during a simulation session.

During a simulation session (also called a planning session), a radiation oncologist maps out the area that needs treatment. The oncologist or radiation technician uses a special CT scanner called a “simulator” because the radiation treatment is being “simulated” or not really given.

For most women diagnosed with cancer in the left breast, lying face down:

  • reduced the amount of heart tissue exposed to radiation by 86%
  • reduced the amount of lung tissue exposed to radiation by 91%

compared to lying face up. While these reductions sound large, it’s important to remember that only a very small area of the heart and lungs might be exposed to radiation while lying face up.

Of course, not all women are built the same. There were a small number of women diagnosed with cancer in the left breast (15%) for whom lying face up actually reduced the amount of heart tissue exposed to radiation compared to lying face down. The researchers didn’t explain why this happened.

For women diagnosed with cancer in the right breast, lying face down:

  • reduced the amount of lung tissue exposed to radiation by 86%

compared to lying face up. Again, while this reduction sounds large, it’s important to remember that only a very small area of the lungs might be exposed to radiation while lying face up.

Still, no matter which position you’re in during radiation therapy treatment, the same principles apply to how the treatment is given. With the most common approach, an external source of radiation treats from two angles: from the middle facing the side, and then from the side facing the middle. These two treatment beams face each other and skim across the chest wall, catching the breast area and minimizing or avoiding radiation to nearby healthy tissue.

When the researchers measured the treatment fields, they found that the treatment fields changed when a woman’s treatment position changed. For most of the women, the treatment field included less heart and lung tissue when lying face down. For some of the women, the treatment field included less heart tissue when they were lying face up.

It’s important to know that advances in radiation therapy have greatly reduced the amount of radiation exposure to the heart, lungs, and other healthy tissue. Besides having women lie face down during treatment, doctors also use computers to plan radiation therapy that is extremely precise in dose and delivery. Some radiation therapy equipment (called respiratory gating) tracks heart beats and lung movement and effectively blocks those tissues from radiation exposure. Other tools, such as intensity modulated radiation therapy, allow the oncologist to change the intensity of the radiation during treatment to avoid healthy tissue.

If you’ve recently been diagnosed with breast cancer and radiation therapy is part of your treatment plan, you may want to ask your doctor about any potential risks for your heart and lungs. Understanding all the risks associated with radiation therapy is more important for women diagnosed with cancer in the left breast who may be deciding between lumpectomy with radiation therapy and mastectomy without radiation therapy.

If you’re going to get radiation therapy for breast cancer, it’s a good idea to ask your radiation oncologist if the technology being used is up to date. Talk to your radiation therapy treatment team about how they’ll make sure that you get only the radiation therapy required to effectively treat the breast cancer. Together, you can plan your treatment to minimize any risks.

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