How Proton Therapy Works

As a method of treating cancer, proton therapy has great potential. But how does it work, exactly, and what makes it superior to other forms of cancer treatment? Tune in and find out.

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Episode Transcript

Speaker 1 (00:00):
Welcome to Brainstuff from how Stuff Works dot com where
smart Happens. I am Marshall Brain with today's question, what
is proton therapy and how does it work? Imagine that
you were to be diagnosed with something like breast cancer,

(00:22):
brain cancer, or prostate cancer. Up until now, your options
have been fairly limited and fairly uncomfortable. The most common
first line of attack is surgery. A surgeon cuts out
the tumor as best he or she can. In the
case of breast, brain, and prostate cancer, this approach can
be fairly problematic. In the case of breast cancer, a

(00:44):
woman may lose one or both of her breasts. In
the case of brain cancer, parts of the brain can
be damaged in the process of getting to the tumor,
or the tumor may not be accessible at all. In
prostate cancer, the patient is often left incontinent and impotent.
In surgery is usually followed by chemotherapy to kill any
remaining cancer cells. Chemotherapy is a drug cocktail that is

(01:09):
in essence poison. The poison kills the cancer cells by
targeting cells that reproduce rapidly. The side effect is that
other cells in the body that happen to reproduce rapidly
like hair follicles, and the cells lining the stomach often
suffer as well. This explains the hair loss and nausea
that often accompanies chemotherapy. Another possibility is X ray therapy,

(01:33):
where multiple beams of X rays penetrate the body and
intersect at the tumor. The tumor receives a high enough
dose of X rays to damage the cancerous DNA and
kill the cancer cells, but there can be collateral damage
at the places where the X ray beams enter the
body and overshoot the tumor. Healthy tissue near a tumor

(01:54):
often gets damaged as well. There are other therapies, including
bits of radioactive serial commonly called seeds, embedded in and
around the tumor in the hope of killing the tumor
with nuclear radiation, various new and experimental drugs targeting things
like tumor blood supply, and so on. Most of the
techniques in use today have side effects that can be

(02:16):
quite unfortunate for the patient. This is why so many
people are getting excited about proton therapy. The idea here
is to use protons, which have been accelerated to near
light speed in a particle accelerator to kill cancer tumors.
The advantage of proton therapy is a good success rate
with a low incidence of side effects. So what is

(02:40):
a proton? If you think of a hydrogen atom, the
proton is the some atomic particle at the core of
the atom. A normal hydrogen atom has an electron orbiting
that proton. By stripping off the electron and leaving behind
a bare hydrogen nucleus, you have a proton that can
be used for proton therapy. Protons are so small that

(03:01):
they can fly through the body doing very little damage,
but they do slow down as they make their way
through tissue. Eventually, the protons come to a stop. Add
or near the stopping point, protons strip electrons off of
nearby atoms, changing important molecules in the process. If a
doctor delivers enough protons to a tumor, cells inside the

(03:23):
tumor die because of this electron activity. Some doctors described
protons as acting like a firecracker, avoiding damage to tissue
surrounding the tumor, but exploding inside the tumor. The reason
is that protons do damage when they come to rest,
So if they come to rest inside the tumor. The
tumor is the only thing to get significant damage from

(03:46):
the protons. The depth that the protons penetrate into the
body can be controlled by their speed. Compared to X
ray therapy, there is no exit dose that can harm
healthy tissue beyond the tumor, and there's only a very
small entry dose. The two big problems with proton therapy
right now are the fact that it is so new

(04:08):
and the cost. There are only a handful of proton
therapy facilities in the United States at the moment, and
these facilities are incredibly expensive, costing hundreds of millions of
dollars to build. The cost is coming from the need
for a complete, highly sophisticated particle accelerator at each facility.
The particle accelerator creates the protons and then accelerates them

(04:32):
to the precise speed needed to reach the tumor. Another
problem is the high number of visits. A typical prostate
cancer tumor might require forty daily visits to a proton
therapy facility over the course of two months, unless you
happen to live in the rare city that has a facility.
This means a long daily commute or a two month

(04:54):
hotel stay along with the cost of the forty sessions,
which can rise into the pends of thousands of dollars.
The hope is that technological advances will lower the cost
of new facilities, making the treatment much more accessible and
less expensive. If that happens, it could open a new
era in cancer treatment. For more on this and thousands

(05:19):
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