Learn about Proton Therapy
What is Proton Therapy?
Proton therapy is a kind of external
beam radiotherapy where protons are directed
at a tumor site. Proton therapy is so effective
because of its ability to accurately target and
kill tumors, both near the surface and deep seated
within the body, while minimizing damage to the
surrounding tissues. For this reason, it is favored
for treating certain kinds of tumors where conventional
X-ray and radiation oncology would damage surrounding
tissues to an unacceptable level.
This is especially
a problem around optical nerves, the spinal cord/central
nervous system, head and neck areas, and the
prostate. This is also particularly important
for pediatric patients where long term side effects,
such as residual occurrence of secondary tumors
resulting from the overall radiation dose to
the body, are of great concern. Because of the
lower dose to healthy tissue, protons have less
severe side-effects than conventional radiation
therapy.
How it Works
Protons exist in the nuclei
of atoms and have electrons orbiting them. For
radiation therapy, physicists separate positively
charged protons from hydrogen atoms by stripping
off the negatively charged electrons. Powerful
magnets then bend the proton stream in to a circular path
and then control then it as the stream is accelerated
to near light speed inside a cyclotron. The speed
of the resulting beam, and therefore its energy,
is measured in electron volts, and the higher
the electron voltage, the heavier the impact
when the beam hits a tumor in a patient's body.
Proton
therapy, like all forms of radiation therapy,
works by aiming the energized particles – in
this case protons – onto the target tumor.
These particles damage the DNA of cells, ultimately
causing their death. Because of their high rate
of division, and their reduced ability to repair
damaged DNA, cancerous cells are particularly
vulnerable to this attack on their DNA.
The difference
in the effectiveness of protons and X-rays is
what takes place before and after radiation reaches
the tumor. X-rays release much of their energy
quickly after penetrating the skin, disrupting
the molecules of healthy tissue and organs. Protons
can be manipulated to release most of their energy
only when they reach their target. Unlike X-rays,
which pass completely through the body, protons
go no farther than the tumor, sparing everything
behind it. More energy reaches the cancerous
cells, so more damage is administered by each
burst of radiation. Side effects caused by the
irradiation of normal tissue in front of and
behind the tumor are not totally eliminated,
but dramatically reduced.
Quick History of Proton
Therapy in the U.S.
- 1930 – Ernest
Lawrence invents the Cyclotron
- 1946 – The first
suggestion that energetic protons could be
an effective treatment method was made by Robert
R. Wilson in a paper published in 1946 while
he was involved in the design of the Harvard
Cyclotron Laboratory
- In 1961, a collaboration
began between the Harvard Cyclotron Laboratory
and Massachusetts General Hospital to pursue
proton therapy
- 1970's – Massachusetts
General Hospital conducts first study on mixed
proton/photon radiotherapy for the treatment
of prostate cancer
- 1980's – Design
and construction began on the 1st dedicated
clinical facility for the Proton Therapy Treatments
at Loma Linda Medical Center in CA
- 1990's – over
25,000 patients treated throughout the worlds
with proton therapy
Why Use Protons?
- Same
tumor killing properties as X-rays
- Decreased
dose to normal tissues by 50-70%
- Decreased
side-effects and complications
- Ability
to treat tumors close to critical organs like
the spinal cord
- With X-rays, 20% of
cancers come back because treatment dose was
too low to be effective
- Possibility
to increase the safe dose delivered to tumors
- Possibility
of increased cure rates
- The ability
to re-treat tumors after recurrences
- The
added ability to treat benign conditions
Applications
of Protons to Treat Cancers
Applications of Protons
to Treat Benign Conditions
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