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Radiation therapy plays a very important role in cancer treatment,
using radiation to kill cancer cells and while causing minimal
damage to normal cells and tissue. More than half of all cancer
patients receive radiation therapy.
The decision to treat a tumor with radiation is based on
the location of the primary tumor and whether the tumor cells
are radiosensitive. Although radiation therapy and surgery
have similar cure rates for some types of cancer, radiation
therapy is preferred to surgery if the patient has a preexisting
condition that makes surgery impossible or if surgery would
require removing part or all of an organ. For example, radiation
therapy may be chosen to treat cancer of the larynx in order
to preserve the voice.
Radiosensitive tumors respond by promptly showing regression
after moderate doses of radiation. Two examples of highly
radiosensitive cancers are leukemia (cancer of the blood cells)
and lymphoma (cancer of the lymphatic system).
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Radiation therapy is most effective
when a tumor is contained, easily accessible, and located
away from major organs of the body. Testicular cancer,
for example, is one of the best candidates for radiation
therapy. During the process of radiation therapy for
testicular cancer, the rest of the body can be easily
protected from the radiation. Radiation can be directed
from all angles to increase the effectiveness of the
treatment.
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Radiocurability means that the normal tissue-tumor relationship
is such that curative doses of radiation can be used without
excessively damaging the normal tissue. Radiocurative tumors
include carcinoma of the cervix, larynx, breast, and prostate.
Radiation may be the only therapy necessary for radiocurative
tumors.
Generally, radiation is directed to the tumor and the immediate
surrounding area. This destroys the main tumor and any nearby
tumor spread. Higher total doses of radiation are needed to
destroy the main tumor; lower doses are given to destroy the
spread of the tumor. Because radiation affects both normal
and cancerous cells, radiation fields are very carefully planned
(by radiation therapists and physicists) to exclude uninvolved
vital organs and tissues. Patients are treated with multiple
small doses of radiation with time in between treatments so
their healthy cells can repair much of the radiation damage.
The doctor in charge of the patient's radiation therapy is
called a radiation oncologist, who develops and prescribes
each cancer patient's radiation treatment plan and makes sure
that every treatment is accurately given. The radiation oncologist
works closely with other physicians and all members of the
radiation oncology team, who are trained in the safe use of
radiation, to make sure the cancer patient gets the best possible
treatment.
Palliative Radiation Therapy
In addition to its curative purposes, radiation therapy may
also be given to relieve pain in cancer patients. For example,
radiation therapy can often relieve the pain caused by secondary
bone cancer despite the uncertainty about how it works. For
palliative purposes, lower doses are given than for curative
treatment, usually over a shorter period of time.
Adjuvant Treatment
In order to achieve the most effective cancer curative results,
radiation treatment is frequently used as adjuvant therapy
to other treatments. Radiation treatment may be administered
before or after surgical treatment. Sometimes, surgery may
effectively remove the gross tumor, but there may be a limit
to the amount of adjacent tissue that can be removed without
impairing function. Post-surgery radiation treatment can be
administered to destroy microscopic residual cancer cells
left after surgery. Sometimes, pre-surgery radiation treatment
is administered to shrink the tumor so that it can be surgically
removed more easily or make the operation less radical, thereby
preserving more normal tissue. Based on studies, better cancer
treatment outcomes result after the combination of radiation
therapy and/or chemotherapy after surgery.
To ensure the success of radiation treatment, the radiation
oncologist tailors each patient's treatment to make sure it
is safe and effective. A careful treatment plan is often made,
and then practiced using a simulator before any actual treatment
begins.
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