Proton Therapy for Breast Cancer

If you have breast cancer, your doctor may recommend radiation therapy as part of your treatment plan. You may need it if you have a mastectomy, the tumor is large, or the cancer has to spread to your lymph nodes or other parts of your body. It may also help prevent the cancer from returning after breast-saving surgery.

The most common type of radiation therapy used to treat breast cancer is external beam radiation. A specialized type of this, called proton therapy, targets just the tumor so the surrounding healthy tissue is less likely to be harmed. Another name for this radiation treatment is intensity modulated proton therapy or IMPT.

It's used to treat cancers near delicate or critical body areas when radiation can affect those areas. Your breasts sit very close to your heart and lungs. Doctors say this kind of therapy can help women get better while lowering the risk of radiation damage to those organs.

How Proton Therapy Is Different

Proton therapy and traditional cancer radiation treatment destroy tumors in the same way: They damage the DNA inside cancer cells.

Standard radiation (X-ray) uses waves of high-energy light called photons to do this. X-rays sprinkle radiation all over your body as they move through you. They don’t stop when they hit your tumor. They keep traveling beyond the treatment area. That can harm healthy body tissue.

Proton therapy uses beams of charged particles called protons to kill cancer. The protons deliver the bulk of their cancer-fighting energy directly to the tumor. And they don’t go beyond the target area. That means you’re less likely to have radiation damage to any tissue near the tumor.

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How It May Help Women With Breast Cancer

Women who have traditional X-ray therapy (or radiotherapy) for left-side breast cancer are more likely to develop ischemic heart disease, a major heart problem caused by narrowed arteries. A 2013 study in the New England Journal of Medicine found that the risk starts about 5 years after treatment and lasts for at least 2 decades. The higher the radiation dose, the greater your risk.

Proton therapy helps avoid this and other complications.

Some other benefits of proton therapy include:

  • It’s painless.
  • It’s non-invasive (no cuts or incisions are needed).
  • It can be used with other cancer treatments.
  • It can be used if you have breast implants.

There are few to no side effects from proton therapy. People seem to handle this type of radiation treatment better than standard radiation therapy.

Types of Breast Cancer It Can Treat

Talk to your doctor about whether your type and stage of breast cancer can be treated with proton therapy.

It may be an option for you if you have:

  • Stage I, II, or III breast cancer
  • Breast cancer that has spread to your chest wall, skin, or underarm lymph nodes but not other organs (locally advanced breast cancer)
  • Breast cancer cells in your lymph nodes (node-positive breast cancer)

You may be a good candidate if you have one of these forms of breast cancer:

  • Estrogen receptor (ER) positive or negative
  • Progesterone receptor (PR) positive or negative
  • HER2/neu positive or negative
  • Triple positive: positive for ER, PR, and HER2
  • Triple negative: not positive for ER, PR, and HER2

Research to learn the benefits of proton therapy for women with breast cancer is ongoing. Medical centers across the country are enrolling people to take part in studies.

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Treatment

Your radiologists and doctors will work together to create a proton therapy treatment plan for you.

A few days before your first treatment, you'll have a simulation session. During this appointment, the radiology team will mark the location for your treatment on your body so they know where to aim the beams. They may draw lines and circles with permanent markers or give you tiny freckle-like tattoos.

During treatment, you need to lie very still so the right amount of radiation gets to your tumor. If you move or shift, the radiation might miss the target area. You might have a frame or cast to help you stay in position. Treatments can last up to 30 minutes.

You’ll have several sessions like this over about 6 weeks.

Where Can I Find Proton Therapy?

A special machine called a cyclotron or synchrotron is needed for proton therapy. Only about 24 centers in the United States offer the treatment. But more proton centers are opening as equipment costs drop and the treatment becomes more popular.

The National Association of Proton Therapy can help you find a proton therapy center.

WebMD Medical Reference Reviewed by Carol DerSarkissian on June 18, 2018

Sources

SOURCES:

American Cancer Society: "External Beam Radiation," "Radiation Therapy for Breast Cancer." 

American Heart Association: "Silent Ischmia and Ischemic Heart Disease."

Bush, D. International Journal of Radiation Oncology. 2014.

Darby, S. New England Journal of Medicine. March 24, 2013.

Florida Proton Therapy Center: "Side Effects of Proton Therapy."

Memorial Sloan Kettering Cancer Center. "Proton Therapy: A Better Way to Destroy Tumors."

National Association of Proton Therapy: "Frequently Asked Questions," "Proton Therapy Centers," "Proton Therapy Fact Sheet."

National Cancer Institute: "Radiation Therapy for Cancer."

Press release, Scripps Health, May 25, 2016.  

Susan G. Komen Foundation: "Locally Advanced Breast Cancer."

University of Florida Health: "Proton Therapy for Breast Cancer Treatment."

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