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Proton Therapy

Advantages and benefits of proton therapy

Both standard X-ray (photon) radiation therapy and proton therapy attack tumors by preventing cancer cells from dividing and growing. The difference between the two treatments is that protons can precisely target the tumor and reduce damage to healthy tissue near the tumor. Protons also offer a better opportunity to increase the treatment dose to the tumor if needed.

Research shows that proton therapy can cause fewer short- and long-term side effects than standard radiation therapy, reducing the occurrence of secondary tumors and improving quality of life for patients.

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 at a glance

  • Proven to be effective in adults and children
  • Causes fewer short- and long-term side effects
  • Reduces the likelihood of secondary tumors caused by treatment
  • Allows potential increase in treatment dose
  • Can be used to treat recurrent tumors even in patients who have already received radiation

Comparison of proton therapy and X-rays/IMRT in breast cancer treatment

With proton therapy, more of the healthy tissue and critical organs are spared from radiation.

The science of proton therapy

X-rays are electromagnetic waves that penetrate tissue, gradually losing energy as they move along. For even the most energetic clinical X-ray beams available, the depth at which the maximum dose of radiation is delivered ranges between 0.5 cm and 3.5 cm. Because tumors are often located deeper than this range, a higher dose is invariably delivered to the normal tissue in front of the tumor. When the X-rays exit the tumor, they continues to deposit radiation dose and affect healthy tissue as it leaves the body. These issues can cause a variety of short- and long-term side effects, some of which can seriously affect quality of life and health.

Protons are heavy charged particles that can be manipulated to release their energy at a precise point. The radiation deposited by a proton beam increases gradually with depth  and then suddenly rises to a peak, known as the Bragg Peak. The Bragg Peak is designed to conform to the tumor. Immediately after that point, the radiation dose falls to zero, which also spares normal tissue on the far side of the tumor volume. It also means that a higher dose often can be delivered, potentially leading to more effective treatment in some cases.

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.
proton vs. x-Ray beams

With X-ray radiation therapy (black line), the radiation dose peaks soon after entering the body and often, long before reaching the tumor, gradually decreases. Healthy tissue surrounding the tumor receives much of the dose. With proton therapy (blue lines), treatment conforms more closely to the tumor, so that less radiation is deposited in the healthy tissue in front of the tumor compared to X-ray therapy, and almost none is deposited in the healthy tissue behind the tumor.

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.

State-of-the-art technology

The cyclotron

The driving force behind proton therapy is the cyclotron. First, electricity is applied to hydrogen gas, causing the atoms to eject protons. The cyclotron then spins these protons at speeds of up to 223 million miles per hour. Magnets then guide a beam of protons from the cyclotron to the treatment rooms.

The treatment rooms

Fred Hutchinson Cancer Center - Proton Therapy offers different rooms customized to meet patient needs. The rooms include the fixed beam, inclined beam and gantry. The room selected for you will depend on your diagnosis and tumor location.

All treatment rooms feature a robotic patient-positioning system, which helps move patients into the exact position each time, ensuring precise delivery of therapy, while minimizing setup time for treatment. The positioning system received U.S. FDA clearance in April 2009 and was named rt image magazine's most valuable product in 2009.

Fixed-beam room

The fixed-beam room uses a horizontal proton beam that’s fixed in place. This system can target and treat the majority of tumors. Although the actual delivery system doesn’t move, the precision and effectiveness of the therapy is identical to that delivered by the inclined beam and the gantry.

Inclined beam room

We have two inclined-beam treatment rooms. The inclined beam is a relatively new technology that can treat approximately 80 percent of the tumors that traditionally required a gantry. This room contains two treatment beams: one positioned horizontally with the beam parallel to the floor, and one at a 60 degree incline from the horizontal.

The gantry

In the gantry room, a 35-foot diameter wheel rotates 360° around the patient, giving our radiation oncologists tremendous flexibility in providing precision treatment. The gantry is particularly effective in treating hard-to-reach tumors, pediatric patients, and anyone who requires a unique course of therapy.

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

Before the protons can be directed into the tumor, dosimetrists create treatment plans for each individual using RayStation. RayStation combines capabilities of traditional imaging such as CTs, PETs and MRIs, with contouring, collapsed cone convolution dose computation and 4D compatibility. RayStation also has unique features such as multi-criteria optimization, dose tracking, treatment adaptation and deformable registration. This specialized software helps to determine how much of a dose should be delivered to the tumor, whether more than one angle will be required, where exactly to deliver the dose, and how best to avoid healthy tissue. RayStation allows our physicians to model treatments and choose the most precise treatment scenario in real time.

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.
Other facts about Proton Therapy at Fred Hutch
  • The building is 57,000 square feet
  • Construction of the building required 13,000 cubic yards of concrete (45 ½ million lbs)
  • Within the concrete are 2 million lbs of rebar (reinforced steel)
  • The building contains 20 miles electrical conduit and 138 miles of wire (enough to go from Seattle to Mt. Rainier)
  • It contains 16 miles of fiber optics
  • The walls between treatment rooms are 5 feet of thick concrete
  • The walls around the cyclotron are 9 feet of concrete
  • The ceiling above the cyclotron is 12 feet of concrete
  • The cyclotron weighs 220 tons
  • The gantry weighs 110 tons and is 30 feet tall, although only 10 feet are visible.
  • The proton beam is around the size of a human hair
Other facts about Proton Therapy at Fred Hutch

Read more about proton therapy and the technology used during treatment.