What Is Proton Therapy?

Proton therapy is an advanced form of radiation therapy designed to kill cancer cells. It involves the use of charged particles called protons rather than the x-rays that are used in conventional radiation therapy. As part of the treatment, also called proton beam therapy, doctors direct cancer-fighting energy to precise locations within the body.

Here are answers to some of the common questions our proton therapy experts hear from patients.

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1. Which types of cancers can be treated with proton therapy?

Proton therapy is most commonly used at MSK to treat head and neck cancer and pediatric cancers. We also are using it increasingly to treat spine tumors, breast cancer, sarcoma, and prostate cancer.

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2. How is proton therapy delivered?

Proton therapy is delivered by a device called a cyclotron, which sends a high-energy beam of protons through the skin toward the tumor. At Memorial Sloan Kettering, the first step is a CT or MRI scan to map the tumor in three dimensions. Then our radiation oncologists, in close collaboration with medical physicists, use computer programs to calculate how to deliver the treatment at the precise dose and location.

You will receive proton therapy in a special treatment room, where you will be positioned on a treatment table. An immobilization device will make sure you stay in the exact position on the table. 

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3. How long do proton treatments last?

Proton therapy treatments usually last about 30 minutes from the time you enter the treatment room to the time you leave. 

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4. How does proton therapy compare with other forms of radiation?

While proton therapy kills cancer cells through a process similar to that used in conventional x-ray radiation — by damaging their DNA. However, because of the unique physical properties of protons, doctors can are able to deliver radiation to a specific depth in the body. With proton therapy, all energy has been released by the time it reaches the tumor site, so there is no dose beyond that point. This can help to reduce side effects.

Proton therapy typically involves the same number of treatments and the same session times as conventional radiation therapy.

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5. What are the benefits of proton therapy?

Because the proton beams do not penetrate beyond the tumor, proton therapy reduces the risk of treatment-related side effects due to radiation damage to normal tissues. Proton therapy may also allow the use of a higher radiation dose to the tumor, maximizing the chance of destroying it.

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6. Why choose Memorial Sloan Kettering for proton therapy?

Proton therapy can be extremely helpful for some patients, while others will not benefit from this type of treatment. The key to proton therapy is to know when it truly is the best treatment option. The medical care team at MSK has experience and access to every form of modern radiation therapy and will recommend proton therapy when it is truly the best choice for the patient. 

Patients at MSK are cared for by a multidisciplinary team of experts — which includes radiation oncologists, medical physicists, oncologists, and surgeons — that is among the most experienced in the world. This team will ensure that each patient receives the optimal treatment for their unique case.

MSK has pioneered several forms of proton therapy for head and neck cancer, prostate cancer, lung cancer, and breast cancer. Our experts are currently using pencil beam scanning technology, which is the most advanced form of proton beam delivery and is available only at select centers. Pencil beam scanning allows proton therapy to be delivered in the most-focused form, reducing exposure to nearby healthy tissues in some cases more than any other form of radiation. 

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7. Where does proton therapy take place at MSK?

Proton therapy is available at a limited number of locations in the United States. Currently MSK doctors deliver proton therapy for appropriate patients at a facility in Somerset, New Jersey. 

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