NCCN Guidelines for Patients® | Prostate Cancer - page 32

32
NCCN Guidelines for Patients
®
: Prostate Cancer
Version 1.2014
Part 4: Overview of cancer treatments
4.2 Radiation therapy
Radiation therapy uses high-energy rays to treat cancer.
The rays damage DNA (
d
eoxyribo
n
ucleic
a
cid). DNA is
a chain of chemicals in cells that contains genes. This
either kills the cancer cells or stops new cancer cells from
being made. Radiation therapy is an option for many men
with prostate cancer. Radiation therapy may be given
to your pelvic lymph nodes as well as to your prostate.
There are two ways to give radiation:
External beam radiation therapy
For prostate cancer, radiation is often given using a
machine outside the body. This method is called EBRT
(
e
xternal
b
eam
r
adiation
t
herapy). To receive EBRT,
you first must have a simulation session. For simulation,
imaging tests are used to help target the tumor with
radiation.
Using the scans, your treatment team will plan the best
radiation dose, number and shape of radiation beams,
and number of treatment sessions. Beams are shaped
with computer software and hardware added to the
radiation machine. Radiation beams are aimed at the
tumor with help from ink marks on the skin or marker
seeds in the tumor.
During treatment, you will lie on a table in the same
position as done for simulation. Devices may be used to
keep you from moving so that the radiation targets the
tumor. You will be alone while the technician operates the
machine from a nearby room. He or she will be able to
see, hear, and speak with you at all times. As treatment
is given, you may hear noises. One session often takes
less than 10 minutes. EBRT is given 5 days a week for
about 8 to 9 weeks, although there is growing interest in
shortening the length of treatment.
There are multiple types of EBRT. For prostate cancer,
3D-CRT (three-
d
imensional
c
onformal
r
adiation
t
herapy)
or IMRT (
i
ntensity-
m
odulated
r
adiation
t
herapy) may be
used. In 3D-CRT, the radiation beams match the shape
of your tumor to avoid healthy tissues. IMRT is a more
precise type of 3D-CRT that may be used especially for
more aggressive prostate cancer. The radiation beam
is divided into smaller beams, and the strength of each
beam can vary.
The prostate can slightly shift within the body. Tumors
may also change shape and size between and during
treatment visits. IGRT (
i
mage-
g
uided
r
adiation
t
herapy)
can improve how well 3D-CRT and IMRT target the
tumor. IGRT uses a machine that delivers radiation and
also takes pictures of the tumor. Pictures can be taken
right before or during treatment. These pictures are
compared to the ones taken during simulation. If needed,
changes will be made to your body position or the
radiation beams.
Often, ADT is used with EBRT. ADT is described in
Part 4.4. Many studies have shown that adding ADT
to EBRT improves treatment outcomes when prostate
cancers are more aggressive. ADT has side effects so it
shouldn’t be used unless necessary. Some men require
short-term (4–6 months) ADT while others are on ADT for
24 to 36 months.
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