Proton Beam Therapy
Protons are hydrogen atoms whose electrons have been
removed. Proton beam radiotherapy uses a special machine called a cyclotron to energize
protons. Protons are extracted from the cyclotron and directed with magnetic fields
to the tumor. How deeply the radiation penetrates is calculated based on the tumor's
location. Protons lose only a small amount of energy when they enter the body. Their
remaining energy is released when they reach the tumor, delivering the most effective
dose of radiation. Proton beams have no exit dose unlike conventional radiation
- What is proton therapy and how is it used?
Protons are atoms that carry a positive charge. Just
as x-rays are used to treat both benign and malignant tumors, a beam of protons
can be used to irradiate tumors in the same way. There is no difference in the biological
effects of protons versus photons (x-rays). Physically, protons release most of
their energy when they hit the tumor and deliver no exit dose beyond the tumor boundary,
unlike photons. Therefore, the dose of radiation conforms to the tumor better and
there is less damage to healthy tissue. As a result, the treating physician (a radiation
oncologist) can potentially give an even greater dose to the tumor while minimizing
unwanted side effects. This is especially important when treating children, because
it reduces radiation to growing and developing tissues.
Proton therapy is being used to treat tumors in these areas of the body with
encouraging early results:
- Spinal or vertebral body tumors
- Skull base sarcomas
- Pediatric brain tumors
- Head and neck
- Eye melanomas
Protocols are being developed to explore the use of protons in other parts of the body.
- Who will be involved in this procedure?
Proton beam therapy requires a treatment team, including a radiation oncologist,
radiation physicist, dosimetrist, immobilization specialist, radiation therapist,
and nurse. The radiation oncologist is a specially trained physician who evaluates
the patient and determines the appropriate therapy, specific area for treatment,
and radiation dose. Working together, the radiation oncologist, radiation physicist,
dosimetrist and radiation therapist establish the best way to deliver the prescribed
dose. The radiation physicist and the dosimetrist then make detailed treatment calculations.
Radiation therapists are specially trained technologists who perform the daily radiation
treatments. Imaging studies are very important in delivering this treatment and
a diagnostic radiologist is often involved with planning, too. Radiation therapy
nurses are team members who tend to your day-to-day concerns and help to manage
the side effects of the treatment.
- What equipment is used?
Proton beam therapy uses a special machine called a cyclotron or a synchrotron to
generate and accelerate protons. The protons leave the machine and are steered by
magnets toward the tumor. Other pieces of equipment are used to modify the range
of the protons, shape of the beam, and to compensate for organ location.
- Who operates the equipment?
With backgrounds in mechanical, electrical, software,
hardware and controls, specialized operators maintain, upgrade and repair the cyclotron
or synchrotron and radiation delivery system. They are also present in the facility's
main control room during treatments in order to monitor the performance of the radiation
- Is there any special preparation needed for the procedure?
Before a patient begins proton therapy, there are a few preparation steps. First,
the patient will be fitted for an immobilization device to put his or her body in
the exact same position for each therapy treatment. The device used will depend
upon the location of the tumor. Patients with a tumor below the neck will have a
full-body mold made of foam liners surrounded by rigid plastic shells. Patients
with a tumor in the eye, brain or head will be fitted with a custom-made mask.
Once the immobilization device is constructed, patients will often undergo computed
tomography (CT) or magnetic resonance imaging (MRI) scanning to create a 3-D reconstruction
of the tumor to define its boundaries with the surrounding normal structures. The
patient wears the device during the CT scan so that it can be taken into account
for treatment planning. Sometimes a CT or MRI scan is done prior to mask-fitting.
In the case of eye melanoma patients with tantalum rings sutured, simple x-rays
may be taken to image the rings' placement.
The radiation oncologist uses a computer to trace the tumor and the surrounding
normal tissues. Physicists and dosimetrists create a treatment plan on the computer
that outlines a single or multiple proton beams entering at various angles. They
use this to calculate the radiation dose that the tumor will receive. After the
physician reviews this plan, it is transferred to automated machines that make the
special devices, apertures and tissue-compensating filters that will be used during
therapy. All of these devices are calibrated by the physics support staff before
the patient's first treatment to ensure that the planning and fabrication have been
- How is the procedure performed?
The procedure is performed on an outpatient basis. The average course of treatment
is usually five to seven weeks, but rarely it may last only a few days. The length
of each treatment will vary depending upon the tumor type and stage. The delivery
of the proton beam to the patient lasts only about a minute, although the total
time spent in the treatment room will be longer (about 15-20 minutes) for positioning
and adjustments to the equipment settings.
For daily treatments, the patient enters the treatment room and is fitted with his
or her personal immobilization device. The patient is positioned with the aid of
laser sights to within a half-centimeter accuracy. The radiation therapist then
takes several low-energy diagnostic radiographs (x-rays) or digital /images to insure
proper alignment. This process is repeated before each treatment. In some cases
a fan beam CT system will be used to image the target before each treatment.
Special apertures and filters that are made for each patient are loaded into the
beam line. A computer may be used to scan and verify the individual bar codes on
these devices. Once positioning and treatment parameters are verified, the radiation
oncologist and technologists step out into a control room located next to the treatment
room and begin the treatment. After the prescribed radiation dose has been delivered,
the computer shuts off the proton beam and the technologists re-enter the room to
assist the patient in removing the mask or immobilization device.
- What will I feel during and after the procedure?
You should not feel any pain or discomfort from the proton beam. Afterward, there
may be some side effects, although these are less frequent and usually less intense
than with standard radiation therapy with x-rays, because there is much less healthy
tissue that is injured. Other factors that may influence how well you feel after
treatment are how big a dose you are given and whether you are also getting chemotherapy
at the same time. Common side effects include temporary hair loss and skin reactions
in the direct path of the radiation and fatigue, especially when a large area is
Side effects of radiation treatment include problems that occur as a result of the
treatment itself as well as from radiation damage to healthy cells in the treatment
The number and severity of side effects you experience will depend on the type of
radiation and dosage you receive and the part of your body being treated. You should
talk to your doctor and nurse about any side effects you experience so they can
help you manage them.
Radiation therapy can cause early and late side effects. Early side effects occur
during or immediately after treatment and are typically gone within a few weeks.
Common early side effects of radiation therapy include tiredness or fatigue and
skin problems. Skin in the treatment area may become more sensitive, red, irritated,
or swollen. Other skin changes include dryness, itching, peeling and blistering.
Depending on the area being treated, other early side effects may include:
- hair loss in the treatment area
- mouth problems and difficulty swallowing
- eating and digestion problems
- nausea and vomiting
- soreness and swelling in the treatment area
- urinary and bladder changes
Late side effects, which are rare, occur months or years following treatment and are often permanent. They include:
- brain changes
- spinal cord changes
- lung changes
- kidney changes
- colon and rectal changes
- joint changes
- mouth changes
- secondary cancer
There is a slight risk of developing cancer from radiation therapy. Following radiation
treatment for cancer, you should be checked on a regular basis by your radiation
oncologist for recurring and new cancers.
Using techniques such as proton therapy, imaging specialists are maximizing the
cancer-destroying capabilities of radiation treatment while minimizing its effect
on healthy tissues and organs and the side effects of the treatment itself.
Proton therapy FAQs
What are protons?
Protons are positively charged particles – the nucleus of the hydrogen atom. In
radiotherapy they enter the human body at a pre-selected energy level and continue
in a straight line up to a precisely calculated depth. While moving, they release
energy with little radiation damage effects. Toward the end of their trajectory
they slow down, coming to rest at the Bragg peak (called after the physicist of
that name), where they release most of their energy and damage the cells. Behind
the Bragg peak the dose reduces to nil after a few millimeters. This physical profile
is the reason for using protons in radiotherapy. It permits deep-seated tumors to
be treated without overshooting the mark.
How does proton therapy work?
Proton radiotherapy works by ionizing tissue molecules, which damages the cell nucleus,
the surrounding membrane and other components, and thereby inhibits cell growth.
Cell division is interrupted or the cell dies.
In comparison with the photons used in conventional radiotherapy, protons have certain
physical advantages. They release their maximum dose – which attacks the tumor cells
– right at the end of their trajectory. The point where they stop is called the
Bragg peak. Their speed (or energy) is calculated so that this point occurs at a
precisely selected spot within the tumor. No radiation is deposited in the healthy
tissue behind the tumor. The dose released in healthy tissue on the way to the tumor
is considerably less than with photon therapy. Therefore, on the one hand the sparing
of healthy tissue is optimal, and on the other a significantly higher radiation
dose can be released precisely within the tumor.
What tumors can best be treated with proton therapy?
Proton therapy is best used where high dose to the tumor and maximum precision is
required. If the medical indications favor lower dose and wide-area radiotherapy,
proton treatment may bring no distinct advantage. In case of doubt, a comparative
therapy plan can be drawn up, and a decision for proton or photon therapy made on
the basis of the calculated dose distributions.
What results has proton therapy achieved? What are the chances of a cure?
Protons have been used in medical therapy since 1954, when patients were first irradiated
with these positively charged particles in Berkeley, California. Since then more
than 50'000 people have been treated at various centers worldwide, mostly for tumors
of the eye (choroid melanomas), brain, skull base, spine and pelvis. Impressive
success has been achieved with eye tumors, with a local tumor control rate exceeding
98% after five years, and there has been a similarly striking increase from 40%
to more than 80% in the control rate for chondrosarcomas and more than 65% for chordomas
of the skull base. These results reinforce the thesis that precise placing of the
radiation dose, along with the significantly higher radiation that can thereby be
released inside the tumor, enable growth to be halted in even relatively radiation-resistant
tumors, or permit them to be destroyed altogether, without damage to surrounding
It is on the basis of these successes that the spot-scanning technique and compact
gantry at SHANGHAI have been developed and built. As facilities spread for treating
tumors that cannot be adequately subjected to conventional radiotherapy, we may
expect from all these sources an increase in the indications for proton-beam treatment.
What are the side effects?
Side effects are divided into acute and long-term effects. They depend both on the
condition of the organs concerned and on the radiation dose to which they are exposed.
Radiation has its effects where the dose is deposited. For example, hair loss will
only occur when the skull is irradiated, and temporary inflammation and discomfort
will generally arise after radiotherapy affecting the mucous membrane of the bladder
or rectum, but as a rule this lasts only a few weeks.
If you need radiotherapy, you will be informed in detail about possible side-effects.
As protons generally release little radiation in healthy tissue, side effects are
minimal and can be treated. Acute effects occur during or immediately after treatment
and generally last only a few weeks. Long-term effects can occur months or even
years after treatment has ended, and are frequently permanent. They then as a rule
need regular treatment and may seriously affect a patient's overall well being.
For this reason great trouble is taken when planning a therapy to avoid radiation
of healthy organs – nerves, skin, brain tissue etc. Protons are ideally suited to
this task, and the rate of long-term complications after proton therapy is low.
Will I feel anything during the therapy?
Proton therapy is painless and does not burn. Patients feel nothing during treatment.
There are rare situations when specific sensory centers in the brain are irradiated,
which can lead to temporary stimulation during treatment, causing e.g. light flashes
or scent sensations.
How long does the therapy last?
A course of radiotherapy usually lasts several weeks, with a relatively large number
of small individual doses given, until the total dose necessary to destroy the tumor
is reached. As a rule this takes 25-37 days of treatment. At SHANGHAI we currently
calculate 4 to 5 days of treatment per week, so a course of therapy lasts from 5
to 9 weeks. On each treatment day the therapy lasts about half an hour, most of
which time is taken up with the exact positioning of the body so that the tumor
can be irradiated with optimally spearing out the surrounding tissue. The proton
irradiation itself only lasts a few minutes.
Where do patients stay during the therapy?
Proton therapy is predominantly an out-patient treatment worldwide. Our patients
live in the apartment nearby for the duration of the treatment. China Medical Tourism
Inc. will help arrange accommodation, including patients accompanied by a relative
How do patients arrange treatment at SHANGHAI?
As a rule patients are referred by their specialist clinic or physician, but in
a number of cases relatives, friends or the patient themselves make the initial
contact. We always take time to discuss the patient's individual situation, and
if proton therapy is indicated, the treatment will take place in consultation with
the patient's own doctors.
What does proton therapy cost?
Proton therapy is still considerably more expensive than conventional radiotherapy.
As both short and long-term side-effects are lower, overall treatment costs should
In the US, patients need to wait for 4 months in making appointment for Proton Beam
Therapy, and cost them $150,000.
In Shanghai, patients may have the same quality of treatment without waiting period,
and cost only for $50,000.
How do I contact SHANGHAI and obtain information?
Contact the China Medical Tourism Inc. at SHANGHAI's Center of Proton Therapy: