Radiation therapy is one of several options
available to those diagnosed with cancer. Otherwise known
as radiotherapy or irradiation, the technique is often used
by doctors to reduce the size of tumors prior to surgery,
but can also be used post-surgery to reduce the probability
of relapse. Radiation therapy is considered a local treatment
since it can be focused on a specific area, such as a cancerous
growth in the lung or breast. However, since it is so precise,
cancerous cells outside of the treatment area can be missed.
The treatment works by applying radiation to a location in
the body. The radiation reacts with the cells in that location
causing damage to their DNA. Cancerous cells consequently
die because they lack the ability to repair the radiation
damage. The damage results in permanent errors in the genetic
code that cause the cells to destroy themselves rather than
replicate. Healthy cells, on the other hand, maintain their
ability to repair the radiation damage, and therefore are
more often able to survive the bouts of radiation therapy.
There are two forms of radiation therapy used by doctors
in the treatment of cancers: external and internal. External
radiation therapy consists of high energy rays of radiation
that are focused on the area receiving treatment. Internal
radiation therapy is also known as brachytherapy. In this
method, radioactive substances are placed inside the body
at the site of the tumor. A radiation oncologist will determine
the exact course of therapy to be used in a person’s
treatment based upon the type of cancer, its location, and
the patient’s personal medical history.
There are several methods of external radiation therapy available
today. Most commonly, a machine called a linear accelerator
is used to create high energy rays of sub-atomic particles.
High doses of x-rays, electron beams, or gamma rays from radioactive
cobalt are also regularly used in treatment. Newer treatments
are also becoming more widely available.
Research has led to the development of radiation treatments
that are much more accurate than older methods, affecting
only the tumor and not healthy surrounding tissues. Among
the newest techniques are Three-dimensional Conformal Radiation
Therapy, Stereotactic Radiotherapy, Cyberknife, the Peacock
System, and Precision Therapy. Most of these methods rely
on imaging of the tumor area and specifically delivered doses
of radiation coming from many different angles of attack.
External radiation therapy only affects the person receiving
the radiation. However, the patient will not become radioactive
from receiving radiotherapy! Patients of radiotherapy can
have close contact with other people without worrying about
transferring radiation. Side effects are usually minimal,
but can include fatigue, decreases in blood cell counts, and
irritation of the skin at the point of radiation. The side
effects experienced are usually specific to the areas being
treated. For example, if the abdomen or stomach receives radiation,
nausea and vomiting should be expected.
Internal radiation therapy is preferred by doctors if they
wish to deliver a high dose of radiation in a short period
of time, and can be used in conjunction with external radiation.
The implants are often referred to as seeds or capsules. They
can be placed directly into the tumor or near a tumor in a
body cavity. This procedure is surgical in nature, and must
therefore be performed under some form of anesthesia in a
hospital. In addition, the radiation being implanted can be
released from the body. So, patients receiving internal radiation
therapy are often isolated in their hospital room, and allowed
visitors on a limited basis for the duration of treatment.
As with external radiation therapy the side effects are minimal,
and depend generally on the location of the radioactive implant.
Kirsten Sanford is a science journalist
& PhD candidate in the Molecular, Cellular and Integrative
Physiology Graduate Group at the University of California,
Davis. In addition to developing patient health education
materials she also hosts a weekly science radio show (This
Week in Science) dedicated to bringing current scientific
news and research to the public.