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Proton Therapy -- Frequently Asked Questions
For Patients and Families
Proton Therapy—a Major Advance in Radiation Oncology
The Basics of Proton Therapy
What is proton therapy?
You've heard of traditional radiation therapy, which has been used for many decades to
treat cancer. Traditional radiation uses X-rays, which are made of light energy, also
called photons. Most people have low-dose X-rays, when your doctor needs images of
your bones or teeth. Higher doses of X-rays are used to target and kill cancer cells.
Proton therapy is a major technological advance in cancer care. It uses protons,
accelerated to about two-thirds the speed of light, or more than 100,000 miles per
second, to destroy cancer cells. Yet it minimizes exposure to nearby healthy tissues.
Like traditional radiation, proton therapy may be used in conjunction with other therapies
such as surgery or chemotherapy
How does radiation attack cancer cells?
Both proton radiation and traditional radiation damage cells' DNA. (When radiation
damages the cells' DNA beyond repair, the cells stop dividing and eventually die.
Radiation primarily kills the cells that are actively dividing. And cancer cells, which tend
to grow out of control, are often dividing. With some forms of radiation, however, other
healthy cells in the path of the radiation also receive the radiation dose.
Does radiation affect only cancer cells?
No, as the American Cancer Society puts it, "radiation therapy is always a balance
between destroying the cancer cells and minimizing damage to the normal cells."1AmCanSoc
It’s difficult to deliver radiation therapy to cancer cells without harming healthy cells
nearby. The shape and location of a tumor can often pose a problem. Tumors can be
irregular in shape, with uneven edges. They may also grow into an organ in fingerlike
projections.
How do doctors decide on the right dose of radiation therapy?
In many instances doctors use as low a dose of radiation as possible to prevent damage
to healthy cells.
An advantage of proton therapy as delivered by the ProBeam® system is that doctors
can precisely program which tissues receive therapy. It's possible to specifically target
the tumor and minimize exposing nearby, healthy tissues. This allows doctors to use
higher levels of radiation in an effort to kill all of the cancer cells.
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How is proton therapy able to deliver energy to the tumor only?
Proton therapy differs from traditional radiation therapy in the way the energy is
delivered to the patient. Protons deliver most of their energy at a prescribed,
programmable distance inside the body, known in physics as the Bragg Peak. As a
result, very little dose is delivered along the path prior to reaching the target
What are the advantages of using proton therapy?
Doctors are better able to:
 Treat tumors next to critical organs while leaving healthy tissues untouched
 Treat irregularly shaped tumors that have grown into or wrapped around organs such
as the eye or brain
 Reduce side effects common with traditional radiation
As the National Cancer Institute says on its proton therapy website, "healthy tissues are
largely spared side effects from treatment and there is greater damage to the tumor.
This may diminish the chance of it coming back or of new tumors in the surrounding
tissue arising later on."2
Proton therapy is used for which types of cancers?
Proton therapy can be used to treat any tumor when radiation is an accepted form of
treatment. It is often used when tumors have not metastasized (spread to other parts of
the body). In addition, it is often used for tumors that are close to other critical structures
such as the:
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Brain
Breast – particularly left breast since
the tumor may by near the heart
Head and neck
Liver
Prostate
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Bone & Soft Tissue
Gastrointestinal
Lung
Ocular
Is proton therapy used only with adults?
Proton therapy is also effective for pediatric patients because it is precisely targeted to
deliver dose only to the tumor. Such precision in therapy can spare nearby organs that
are still growing and developing, which may prevent future side effects. This factor has
added importance because pediatric patients have so many years of post-treatment
years ahead of them. Therefore, proton therapy may offer benefits for certain childhood
cancers.6
What are the side effects from proton therapy?
.A person doesn't feel anything from the proton therapy itself—there is no pain from the
treatment. However, some people might feel uncomfortable just from having to lie still on
the table during treatment.
After any type of radiation therapy, patients may feel some side effects such as irritation
to the respiratory, digestive, urinary or reproductive systems, fatigue, nausea, and skin
irritation. However proton therapy often leads to lead to fewer side effects than traditional
radiation. For instance a recent study of 582 patients, treated for esophageal cancer,
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showed that patients had significantly fewer toxic side effects than patients treated with
older radiation therapies.7
Side effects can last for some time after the treatments end. This is because cells
continue dying for weeks or even months after radiation therapy ends.
What imaging tests are needed beforehand?
Patients will go for an appointment with the radiation oncologist (a doctor specializing in
radiation to treat cancer). Treatment planning begins with simulation. During simulation,
detailed images are taken, showing the location of the tumor and the normal tissues
around it. The 3D images show the oncologist how to best target the tumor with proton
therapy. These images are usually produced with computed tomography (CT) scans.
However, some of the other tests listed below could be used too.
CT (computed tomography) scan: uses an X-ray linked to a computer to create a
series of detailed, cross-sectional images, or slices, of areas inside the body. Crosssectional pictures are created since the images are taken from many different angles.
Contrast material containing iodine is sometimes used for better images. CT scans, also
called CAT scans, which offer more details than regular X-rays do, are often used for
bones, blood vessels, and soft tissues inside the body.
Ultrasound scan: uses high-energy sound waves to bounce off internal tissues or
organs and make echoes. The echo patterns are used to form an image of body tissues.
MRI (magnetic resonance imaging): uses radio waves and a powerful magnet linked
to a computer to create detailed images. These images can show the difference
between normal and diseased tissue inside the body. MRI creates clearer images of
organs and soft tissue than other scanning techniques (such as CT scans or X-rays).
MRI is especially useful for imaging the brain, the spine, the soft tissue of joints, and the
inside of bones.
PET (positron emission tomography) scan: after a small amount of radioactive dye is
injected into a vein, a scanner creates detailed, computerized images of areas inside the
body where the dye is present. The images can help find cancer cells in the body. Unlike
CT scans or MRIs, which look at anatomy, PET scans look at metabolic activity or body
function. As a result, PET scans can detect tumors in lymph nodes, for example, even
before they enlarge and can be seen with MRI or CT.
In what other ways do patients need to prepare before proton therapy is given?
Once the doctor studies these detailed images, she or he determines the best angles (or
fields) for the proton therapy to be delivered. It's critical to ensure that the patient will be
in exactly the same position each day therapy is given. To help the patient lie still on the
treatment table, sometimes body molds or head masks are used. Temporary skin marks
or tattoos may also be used to help with precise patient positioning.
Which medical professionals are involved?
The radiation oncologist is the doctor who specializes in radiation therapy. (An
oncologist is a doctor specializing in cancer treatment.) The radiation oncologist is your
doctor during treatment, doing the following:
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Examining the detailed images of the tumor
Deciding which radiation type to use and how to best prescribe the therapy based on
the size and shape of the tumor
Prescribing, planning, and directing the treatment
The medical physicist works with the radiation oncologist and the dosimetrist (see
below) to measure the precision of your treatment plan. The medical physicist also does
safety checks and makes sure that the equipment is working properly.
The dosimetrist works closely with the radiation oncologist and the medical physicist to
design your treatment plan. The dosimetrist determines how to best avoid giving
radiation to healthy tissue near the tumor.
The radiation therapist delivers the treatment during each session. He or she positions
you on the treatment table, operates the equipment, and works closely with the medical
physicist during treatment.
The radiation nurse coordinates your care, helps you learn about treatment, and tells
you how to best manage any possible side effects.
How long will proton treatments take?
It varies depending on the cancer. Therapy often takes place Monday through Friday
over several weeks. For instance at once center, Scripps Hospital, people get treatment
five days a week for four to eight weeks. Each treatment session takes about 15-25
minutes. Most of that time is to adjust the machine and position the patient. The actual
treatment with protons often takes less than a minute.
Do most oncologists have experience with proton therapy?
Most oncologists (cancer doctors) know about proton therapy. However since there are
fewer than 10 proton centers in the US using the newest form of proton therapy, pencil
beam scanning, they may not have direct experience with it.
Is proton therapy covered by insurance in the United States?
Nearly all insurance companies in the United States cover proton therapy, as do
Medicaid and Medicare. If you and your doctor think that proton therapy is a good option
for you, ask about insurance coverage.
Getting Help from the Proton Center Staff
Proton centers typically have staff members who can help you find out if your insurance
covers proton therapy. With your approval, they can contact your insurance company to
learn if you're eligible for coverage, and what the insurance company requires for
deductibles, co-payments, and maximum out-of-pocket costs.
The proton center staff may also be able to work with you to answer insurance
companies' questions and to get prior authorization for your treatment. If needed, the
staff may be able to help you obtain coverage—for instance, by submitting a document
called a "letter of medical necessity."
If coverage is at first denied by the insurance company, that's not always the final
answer. Repeated queries may succeed. That may especially be the case if your doctor
can provide evidence that proton therapy is appropriate for you, and if it has successfully
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treated other patients with your condition. You might talk to your insurer, doctor's office
staff, and the hospital business office to find out who can best help you with your
insurance company.
For you as a patient, there should be no difference in out-of-pocket costs for proton
therapy versus other kinds of radiation therapy, assuming that your treatment meets
your insurance company's criteria. In fact people receiving proton therapy often have
little to no out-of-pocket expenses—once they meet the policy's deductibles and yearly
maximum out-of-pocket costs.
Looking at Total Costs and Quality of Life
It's also important for you and your doctor to consider all of the costs and the side effects
of various forms of treatment before making the final decision on the best course of
treatment for you. Some questions you might want to ask your doctor include:
 How will some of the treatment options affect my life in the short or long term? (For
example, someone with certain kinds of head/neck cancer might ask whether certain
therapies are more likely to result in damage to salivary glands, the need for a
feeding tube, etc.)
 What could offer me the best post-treatment quality of life, with fewest side effects
and less pain—and could this also affect the my healthcare costs over time?
 What could be the total costs of various forms of therapy—not just the surgery or
radiation therapy, but the need for follow-up doctor's appointments or hospital visits?
Cost is one consideration when deciding on treatment, but short- and long-term quality
of life are other critical considerations.
How long has proton therapy been used?
Proton therapy to treat cancer was first proposed by Dr. Robert R. Wilson just after
World War II.8 Patients have been treated with proton therapy since 1990, but pencil
beam scanning has been used commercially only since 2009.
It's estimated that new cancer cases will grow to over 20 million by 20301 and, if
treatment patterns parallel today's patterns, 60-75% of cancer patients will receive
radiation therapy.2 Many proton centers are in the planning or construction phases,
since proton therapy is increasingly an option in cancer care.
How do I know if proton therapy is right for me?
Everyone's situation is different. You need to talk to your doctor to decide on the type of
radiation therapy that's best for you.
What should I ask my doctor about proton therapy?
 What stage is the cancer?
 Is the cancer in one small area or has it spread to other parts of the body?
 Is radiation a good option for my treatment?
 Do you recommend chemotherapy and/or surgery too?
 Regarding radiation: do you recommend traditional radiation or proton therapy?
 Would proton therapy—since it may spare healthy tissues nearby—make any
difference in my situation?
 Where is the nearest cancer center that offers proton therapy?
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How can I best avoid side effects? And what side effects can I expect with the type of
radiation you recommend?
How quickly should I begin the treatment(s)?
Different Types of Proton Therapy: Pencil Beam Scanning vs
Passive Scattering
Is all proton therapy alike?
No, there is a key difference in the way the beam of proton radiation is delivered. The
two ways that proton therapy can be delivered:
 Passive scattering. Because this is an earlier form of proton therapy, first used in the
1980s, it is used in most proton centers.
 Pencil beam scanning, or spot scanning. This is a newer, more advanced type of
delivery.
How does pencil beam scanning differ from passive scattering?
Pencil beam scanning offers several benefits over passive scattering:
 It can deliver high doses of proton radiation therapy
 It conforms to the complex shape of an individual tumor—and therefore can be
used for tumors next to critical structures
 It spares more healthy tissues next to the tumor
 It delivers less radiation to normal, healthy tissue
 It penetrates precisely, which helps when treating deep-seated and/or complex
tumors
 In the vast majority of cases, it does not require beam-modifying devices (large,
heavy devices are needed—for each individual patient—to shape the proton
beam when using passive scattering)
 It is the only type of proton therapy that can deliver intensity-modulated proton
therapy (IMPT), the most advanced form of proton therapy treatment
Varian's ProBeam system stands apart from other proton therapy systems in that it uses
only highly precise pencil beam scanning.
Why is pencil beam scanning so precise?
Before delivering pencil beam scanning, a doctor takes 3D images to know the exact
shape, size, and depth of the tumor. Therapy is then delivered to that precise shape,
size, and depth. As the name "pencil beam" suggests, the beam is very narrow and can
zero in on the tumor with great precision.
Pencil beam scanning deposits radiation on the tumor layer by layer, almost like
"painting" the tumor. This layering helps the therapy conform very closely to the tumor's
shape. You can also view an example of how this works. [LINK
https://www.varian.com/oncology/products/treatment-delivery/probeam-proton-therapysystem]
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How Varian Proton Therapy Technology Stands Apart
How does Varian stand out as an industry leader?
As the world's leading manufacturer of medical devices and software used to treat
cancer and other conditions with radiation, Varian has been pioneering advances in
radiation technology for over 65 years. It is the only radiation oncology company to offer
the full suite of oncology treatment solutions, including proton therapy.
Leadership in Pencil Beam Scanning for Proton Therapy
 It created the world’s first commercially available proton system to deliver pencil
beam scanning (PBS).
 It is the first company to invest in and to exclusively use PBS.
 Its PBS technology has been used to treat thousands of patients since 2009.
 It continually advances intensity-modulated proton therapy (IMPT) technology
through ongoing investment and research.
 It is helping to set the standard for proton technology.
Leadership in Radiation Oncology
 It has more than 65 years of providing scientific innovations that save lives.
 It is the world's leading manufacturer of medical devices and software used to
treat cancer and other conditions with radiation.
 It specializes in products for radiotherapy, proton therapy, radiosurgery, and
brachytherapy.
Leadership in the Corporate Environment
 It is working to offer emerging countries the quality of care that can be found in
developed countries.
 It continues in the tradition of Varian’s founders, who set out to create a company
that found ways of using focused energy to solve human problems. Corporate
decisions are based on the idea of “doing well” while “doing the right thing.”
Leadership for the Environment
 It is rated among the greenest companies in the U.S. by the influential Newsweek
Green Rankings.
 It is the highest ranking medical device company in the 2015 Corporate Knights
Global 100, which ranks the Global 100 of Most Sustainable Companies.
 It is aggressively working towards marked reductions in carbon footprint,
greenhouse gases, energy use, water consumption, and solid waste disposal.
Varian as a Pioneer in Its Early Years
Varian Medical Systems’ mission is to focus energy on saving lives—and it has been
doing so since the Varian brothers began channeling their creative ideas into new
products in the 1930s.
 Brothers Russell and Sigurd Varian developed the first klystron—allowing creation of
a new type of microwave radar system that was light enough to be used in aircraft.
This radar is credited in part with helping the Allies win World War II. (A klystron is a
linear beam vacuum tube.)
 The Varian brothers founded one of the first high-tech companies in the Silicon
Valley of California.
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The company that they formed in 1948—initially with just six employees—went on to
make linear accelerators for photon radiation therapy.
Ion pumps and other Varian technology played a key role in helping astronauts land
on the moon in 1969.
Varian is an industry leader, with a singular focus on saving lives.
The Varian ProBeam System
What are the parts of a Varian proton system?
The ProBeam® system has the following components:
 Superconducting cyclotron—a particle accelerator that uses electromagnetic
waves to speed up the protons. A cyclotron like the one used in the ProBeam®
system has a constant rather than pulsed beam, consumes less energy, and
features a smaller size and footprint compared to most other proton systems'
particle accelerators.
 Beam transport system or beamline—magnets guide the high-energy protons
toward the treatment room through the beamline.
 Treatment room—area that includes the gantry and the treatment table, where
proton therapy is delivered to the patient. A Varian proton treatment room—
measuring about 16.5 feet (5 meters) x 11.5 feet (3.5 meters)—is large enough
that you won't likely feel confined. And there's enough space for the radiation
therapist to move easily around you.
 Gantry—a steel structure that moves around the patient, the gantry has a nozzle
that delivers the proton therapy. The ProBeam system has a gantry that rotates
190⁰ in each direction, allowing treatment to be delivered at any angle without the
need for patient repositioning.
 Treatment table—the robotic treatment table can be adjusted in six planes, to
position the patient precisely based on 3D images. It can be operated from inside
the treatment room or remotely from the control room.
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1
American Cancer Society. The Science Behind Radiation Therapy. 2014.
www.cancer.org/acs/groups/cid/documents/webcontent/003019-pdf.pdf Accessed June 21,
2015.
2
National Cancer Institute. Proton Therapy for Cancer. http://www.cancer.gov/aboutcancer/treatment/research/proton-therapy. Accessed September 18, 2015.
3
Pedroni E. Treatment delivery systems: pencil beam scanning. In: De Laney TF, Kooy HM, eds.
Proton and Charged Particle Radiotherapy. Philadelphia: Lippincott Williams & Wilkins; 2008.
4 Zhang
X, Li Y, Pan X, et al. Intensity-modulated proton therapy reduces normal tissue doses
compared with intensity-modulated radiation therapy or passive scattering proton therapy and
enables individualized radical radiotherapy for extensive stage IIIB non-small cell lung cancer: a
virtual clinical study. Int J Radiat Oncol Biol Phys. 2010;77(2): 357–366.
5 Frank
SJ, Cox JD, Gillin M, et al. Multifield optimization intensity modulated proton therapy for
head and neck tumors: a translation to practice. Int J Radiat Oncol Biol Phys. 2014;89(4)846–
853.
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Chang AL, Yock TI, Mahajan A, et al. Pediatric proton therapy: patterns of care across the
United States. Int J Particle Ther. 2014;1(2):357-367.
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Chuong M, et al. A multi-institutional analysis of acute toxicity after neoadjuvant chemoradiation
using photons or protons in trimodality esophageal cancer patients. Abstract and oral
presentation at the 2015 Conference of the Particle Therapy Cooperative Group North America
(PTCOG).
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Wilson RR. Radiological use of fast protons. Radiology. 1946:47:487-491. doi:
http://dx.doi.org/10.1148/47.5.487
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