Proton Therapy

What is proton therapy?

Proton therapy is an advanced and highly precise form of radiation treatment. It allows Fred Hutchinson Cancer Center physicians to focus radiation right into your tumor. This means we can treat the cancer with the goals of limiting damage to your healthy tissue and lowering your risk of short- and long-term side effects.

Proton therapy may also lower the chance of secondary tumors (tumors that can develop after a patient gets radiation therapy) and improve patients’ quality of life.

Proton radiation therapy can be a highly effective option in place of standard X-ray radiation therapy for a wide range of solid tumors. Precise targeting gives protons a key advantage when we treat tumors that are near vital organs.

Radiation therapy The use of high-energy radiation from X-rays, gamma rays, neutrons, protons and other sources to kill cancer cells and shrink tumors. The use of high-energy radiation from x-rays, gamma rays, neutrons, protons and other sources to kill cancer cells and shrink tumors. Radiation may come from a machine outside the body (external-beam radiation therapy), or it may come from radioactive material placed in the body near cancer cells (internal radiation therapy or brachytherapy). Systemic radiation therapy uses a radioactive substance, such as a radiolabeled monoclonal antibody, that travels in the blood to tissues throughout the body. Side effects A problem that occurs when treatment affects healthy tissues or organs. Some side effects of cancer treatment are nausea, vomiting, fatigue, pain, decreased blood cell counts, hair loss and mouth sores.

Benefits of Proton Therapy

Proven to be effective in adults and children
Causes fewer short- and long-term side effects
Reduces the chance of secondary tumors caused by treatment
May allow you to get a higher, more effective treatment dose
Can be used for tumors that came back, even if you already had radiation therapy

Sparing Healthy Tissue: Proton Therapy vs. X-Ray Radiation Therapy for a Brain Tumor

These pictures show treatment for a brain tumor. The colored areas get radiation. The black, gray and white areas do not. With proton therapy (left), less healthy tissue is exposed to radiation. With standard X-ray radiation therapy (right), more healthy tissue is exposed.

The illustration shows the difference between proton therapy on the left, where fewer healthy tissues are subjected to radiation, and standard X-ray radiation on the right, where more radiation affects surrounding, healthy tissue.

Frequently Asked Questions

How is proton therapy different from standard radiation treatment?

Both standard radiation therapy and proton radiation therapy keep cancer cells from dividing and growing. Both treatments can destroy benign and malignant tumors. The difference is that your care team can make proton therapy fit the size and shape of your tumor more exactly. The goal is to do less damage to nearby healthy tissue.

X-rays are rays of energy that go into the body and then exit out the other side. Because they give off the most radiation where they enter your body, they may damage healthy tissue and organs on their way to your tumor. They can also damage healthy tissue as they keep moving through your body beyond your tumor. (This radiation is called the exit dose.)

Protons are charged particles, not rays. Physicians can direct protons to go into your body, give off the most radiation when they reach your tumor and stop right there. Less radiation hits the healthy tissue in front of your tumor. Almost none reaches the healthy tissue beyond your tumor. (There is little to no exit dose compared to standard radiation therapy.) Less damage to healthy tissue can mean fewer side effects, better quality of life and better long-term health.

Because your healthy tissue gets much less radiation with protons, physicians can often give a higher dose, if it is needed. Research has shown that higher doses of radiation are linked with better cure rates.

Benign Not cancer. Benign tumors may grow larger but do not spread to other parts of the body. Radiation therapy The use of high-energy radiation from X-rays, gamma rays, neutrons, protons and other sources to kill cancer cells and shrink tumors. The use of high-energy radiation from x-rays, gamma rays, neutrons, protons and other sources to kill cancer cells and shrink tumors. Radiation may come from a machine outside the body (external-beam radiation therapy), or it may come from radioactive material placed in the body near cancer cells (internal radiation therapy or brachytherapy). Systemic radiation therapy uses a radioactive substance, such as a radiolabeled monoclonal antibody, that travels in the blood to tissues throughout the body. Side effects A problem that occurs when treatment affects healthy tissues or organs. Some side effects of cancer treatment are nausea, vomiting, fatigue, pain, decreased blood cell counts, hair loss and mouth sores.

How do you target the tumor?

Since every tumor is different, your care team starts by doing a computed tomography (CT) scan of your tumor. This allows your team to see right where to send radiation and which tissue to avoid. Then our physicists, dosimetrists and radiation oncologists work together to make a treatment plan just for you. Your plan maps out the direction, angle and dose of the proton beam.

What kind of cancers does proton therapy treat? Who could benefit?

Physicians use proton therapy to treat many types of solid tumors. These include cancers of the brain, spinal cord, gastrointestinal tract, head and neck, breast, lung and prostate, as well as sarcomas. Please see the Diseases Treated section for a more complete list.

Patients with tumors near vital organs or other important structures benefit most. Proton therapy can also be a good option if your cancer has come back or you have tried all other treatments. It can be an important treatment for children, too.

Gastrointestinal Refers to the stomach and intestines. Also called GI.

Why is proton therapy a good option for children with cancer?

Proton therapy is very useful in treating children. That’s because they are still growing and are more sensitive to the long-term effects of radiation, like damage to healthy tissue. For example, when a child has a brain tumor, it is important to avoid sending radiation to the healthy part of their brain because it needs to keep developing.

With proton therapy, the goals are to lower the amount of radiation to healthy tissue and reduce the chance of side effects, such as growth and development problems or secondary tumors later in life. Fred Hutchinson Cancer Center – Proton Therapy has radiation oncologists who specialize in proton therapy for children.

Radiation oncologist A physician who has special training in using radiation to treat cancer. Side effects A problem that occurs when treatment affects healthy tissues or organs. Some side effects of cancer treatment are nausea, vomiting, fatigue, pain, decreased blood cell counts, hair loss and mouth sores.

Can proton therapy be used along with other cancer treatments?

In many cases, yes. Proton therapy can be used along with chemotherapy, immunotherapy and X-ray radiation and as a follow-up to surgery. Our physicians can talk with you about any other treatments you might need along with proton therapy.

Chemotherapy Treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. It may be given alone or with other treatments. Treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. Chemotherapy may be given by mouth, injection, infusion or on the skin, depending on the type and stage of the cancer being treated. It may be given alone or with other treatments, such as surgery, radiation therapy or biologic therapy. Immunotherapy A type of therapy that uses substances to stimulate or suppress the immune system to help the body fight cancer, infection and other diseases. A therapy that uses substances to stimulate or suppress the immune system to help the body fight cancer, infection and other diseases. Some immunotherapies only target certain cells of the immune system. Others affect the immune system in a general way. Types of immunotherapy include cytokines, vaccines, bacillus Calmette-Guerin (BCG) and some monoclonal antibodies.

Are there government safety regulations for proton therapy facilities?

Yes. Proton therapy facilities fall within state and federal regulatory statutes that require all radiation-production facilities to be licensed. The regulations are the same as for X-ray therapy. Fred Hutchinson Cancer Center – Proton Therapy meets all state and federal standards.

Pencil-Beam Scanning

Our radiation oncologists use pencil-beam scanning (PBS) to treat patients with proton therapy. PBS “paints” your tumor with a lot of very thin, very exact beams of protons. The beams are accurate down to millimeters. PBS sends very fast pulses of protons to each planned spot within the tumor until the whole tumor is treated. This method can lower the amount of radiation to healthy tissue even more.

Fred Hutchinson Cancer Center – Proton Therapy offers PBS in all of our treatment rooms, including the gantry, which lets physicians target tumors from nearly any angle.

Radiation oncologist A physician who has special training in using radiation to treat cancer.

Dr. Jing Zeng, medical director at Fred Hutchinson Cancer Center – Proton Therapy, explains the advantages of pencil-beam scanning using prostate cancer as an example.

“PBS is the most advanced way to deliver proton radiation and allows us to more precisely sculpt protons to treat more complex tumors, such as in the head and neck, lung, abdomen and pelvic areas.”

— Smith Apisarnthanarax, MD, radiation oncologist

Fast, Painless, Noninvasive

Proton therapy treatments are safe, noninvasive (no cuts into your skin are needed) and painless for most patients. You do not need to stay overnight in the hospital. Most patients get treatment five days a week for one to nine weeks. The number of treatments you need will depend on the location and size of your tumor. Treatment sessions last from 15 to 60 minutes. The actual treatment time is only about one minute. The rest of the time is used to get you ready and position you so your treatment is as exact as it can be. Most patients go about their normal routine before and after each treatment.

Getting Proton Therapy Treatment

Researched and Perfected for More Than 60 Years

More than 200,000 people worldwide have had proton therapy at facilities in Europe, Asia and the United States. Proton therapy was first used to treat patients in 1955 in a research setting. But its use was limited because imaging techniques at the time could not accurately locate tumors. After advances in imaging, the U.S. Food and Drug Administration approved proton therapy for clinical use in 1988. The first hospital-based treatment facility opened in Loma Linda, California, in 1990. Fred Hutchinson Cancer Center – Proton Therapy opened in 2013.

Imaging In medicine, a process that makes pictures of areas inside the body. Imaging uses methods such as X-rays (high-energy radiation), ultrasound (high-energy sound waves) and radio waves.

The Science of Proton Therapy

Standard radiation therapy uses X-rays. X-rays are electromagnetic waves that go through tissue, gradually losing energy as they move along. The highest dose of radiation is deposited about 0.5 centimeters (cm) to 3.5 cm deep in the body. Tumors are often located deeper than this range. This means a higher dose of X-ray radiation often gets delivered to the normal tissue in front of the tumor than to the tumor itself. As the X-rays exit the tumor, they keep depositing radiation in the healthy tissue beyond. For these reasons, X-ray radiation therapy can cause both short- and long-term side effects. Some of these side effects can seriously affect quality of life and health.

Protons are heavy charged particles that can be controlled to release their highest energy at a precise depth in the body. The radiation deposited by a proton beam increases gradually as it moves deeper into the body. Then, it suddenly rises to a peak, known as the Bragg Peak. Your team designs your treatment so the Bragg Peak conforms to your tumor. Right after the peak, the radiation dose falls to zero, sparing normal tissue on the far side of your tumor. Because proton therapy is so precise, your doctors may be able to give you a higher dose of radiation, which can be more effective in some cases.

A graph compares the dose distribution for proton and X-ray beams.

With X-ray radiation therapy (black line), the radiation dose peaks soon after entering the body. Then it gradually decreases, often long before reaching the tumor. Healthy tissue around the tumor receives much of the dose instead. With proton therapy (blue lines), treatment conforms more closely to the tumor. This means less radiation is deposited in the healthy tissue in front of the tumor compared to X-ray therapy. Almost none is deposited in the healthy tissue beyond the tumor.

The Science of Proton Therapy

Get a deeper understanding of how X-ray radiation therapy and proton therapy differ and what makes protons more precise.

The History of Proton Therapy

1895
German physicist W.C. Roentgen discovers X-rays, making detection of tumors in the body much easier and noninvasive. Roentgen later wins the Nobel Prize in physics for this discovery.

1919
British physicist Ernest Rutherford demonstrates the existence of protons (elementary particles found in atoms).

1931
American physicist Ernest O. Lawrence invents the cyclotron, a machine used in proton therapy, which accelerates charged particles to high energy levels.

1937
The first clinical use of X-ray radiation therapy is carried out for the treatment of a patient with leukemia at the University of California at Berkeley. Congress passes the National Cancer Institute Act that authorizes annual funding for cancer research in the United States.

1946
American physicist Robert Wilson publishes a study that suggests protons could be used to treat cancer because they are capable of delivering an increased dose of radiation to a tumor while decreasing radiation exposure to surrounding healthy tissue at the same time.

1948
The first proton therapy experiments are done at the University of California at Berkeley. Tumors are effectively removed from the chest and lungs of animals.

1954
The University of California at Berkeley treats the first human patient with protons. Patients are treated with protons at other research institutions, including Harvard University in Boston.

1980s
Advances in imaging technology, including CT, MRI and PET scans, help researchers to better diagnose and see tumors. This makes proton therapy, which requires identifying the precise location of a tumor, a more practical treatment option.

1988
The FDA approves proton therapy as a cancer treatment option.

1990
The first hospital-based proton treatment facility in the United States is built at Loma Linda University Medical Center in Loma Linda, Calif.

2001
The first patient is treated at Harvard/Massachusetts General Hospital’s Francis H. Burr Proton Therapy Center in Boston, the second hospital-based proton treatment facility in the United States.

2003
The Midwest Proton Radiotherapy Institute (now the Indiana University Health Proton Therapy Center), the third proton treatment facility in the United States, opens in Bloomington, Indiana.

2005–2010
Seven more institutions open proton therapy facilities in the United States.

2013
On March 8, 2013, SCCA Proton Therapy Center (now Fred Hutchinson Cancer Center – Proton Therapy) opens in Seattle. It is the first proton facility in the Northwest (and was the only one within a 1,000-mile radius when it opened).

Computed tomography A procedure that uses a computer linked to an X-ray machine to make a series of detailed pictures of areas inside the body. The pictures are used to create three-dimensional (3-D) views of tissues and organs. A procedure that uses a computer linked to an X-ray machine to make a series of detailed pictures of areas inside the body. The pictures are taken from different angles and are used to create three-dimensional (3-D) views of tissues and organs. A dye may be injected into a vein or swallowed to help the tissues and organs show up more clearly. This scan may be used to help diagnose disease, plan treatment or find out how well treatment is working. Imaging In medicine, a process that makes pictures of areas inside the body. Imaging uses methods such as X-rays (high-energy radiation), ultrasound (high-energy sound waves) and radio waves. Magnetic resonance imaging A procedure in which radio waves and a powerful magnet linked to a computer are used to create detailed pictures of areas inside the body. A procedure in which radio waves and a powerful magnet linked to a computer are used to create detailed pictures of areas inside the body. These pictures can show the difference between normal and diseased tissue. MRI makes better images of organs and soft tissue than other scanning techniques, such as computed tomography (CT) or X-ray. MRI is especially useful for imaging the brain, the spine, the soft tissue of joints and the inside of bones. Radiation therapy The use of high-energy radiation from X-rays, gamma rays, neutrons, protons and other sources to kill cancer cells and shrink tumors. The use of high-energy radiation from x-rays, gamma rays, neutrons, protons and other sources to kill cancer cells and shrink tumors. Radiation may come from a machine outside the body (external-beam radiation therapy), or it may come from radioactive material placed in the body near cancer cells (internal radiation therapy or brachytherapy). Systemic radiation therapy uses a radioactive substance, such as a radiolabeled monoclonal antibody, that travels in the blood to tissues throughout the body. Radiation therapy The use of high-energy radiation from X-rays, gamma rays, neutrons, protons and other sources to kill cancer cells and shrink tumors. The use of high-energy radiation from x-rays, gamma rays, neutrons, protons and other sources to kill cancer cells and shrink tumors. Radiation may come from a machine outside the body (external-beam radiation therapy), or it may come from radioactive material placed in the body near cancer cells (internal radiation therapy or brachytherapy). Systemic radiation therapy uses a radioactive substance, such as a radiolabeled monoclonal antibody, that travels in the blood to tissues throughout the body.

The History of Proton Therapy

See a timeline of how proton therapy evolved from the early days of standard radiation in medicine through the opening of Fred Hutchinson Cancer Center – Proton Therapy.

Back To: Proton Therapy

Next Up: Getting Proton Therapy Treatment