NCCN Guidelines for Patients
Rectal Cancer, Version 1.2017
Overview of cancer treatments
For rectal cancer, the most common radiation
method is EBRT (
A large machine makes high energy x-rays used for
treatment. This machine is called a LINAC (
See Figure 11
The beams of high-energy x-rays are a type of
photon radiation. They will move through your body
at the speed of light. There is no ongoing radiation
inside of you after the treatment session. You will not
have to avoid people.
It takes a team of people to perform the radiation
therapy. The radiation team consists of doctors,
medical physicists, dosimetrists, nurses, and
radiation therapists. Your team will work together to
design your treatment plan and provide treatment.
A planning session is needed to map out your
treatment. The planning process is called simulation.
It involves obtaining a CT scan of your body in the
position that is needed for treatment. The scan is
only used for treatment planning.
You will not have to do much to prepare. Don’t eat
a heavy meal for 4 hours beforehand. Think about
wearing easy-to-remove clothes since you’ll undress
from the waist down. You’ll wear a gown during the
session. The planning session takes about one hour.
In the CT room, a mold may be created and fitted
to your body. The mold will help you stay in place
during treatment. Often, people lie face down on the
mold that is on top of the CT table. Your arms may be
raised above your head. Colored laser lights will be
used to help position you.
You may be given a contrast dye. It will make your
rectum and lymph nodes easier to see on the
scans. Contrast may be given with a rubber catheter
inserted into your rectum. Air may also be pumped
in or removed. Next, a CT scan will be done. The
medical physicist or dosimetrist may take more
measurements for treatment planning.
The CT images will be transferred to a treatment
planning computer. Your rectum and other organs will
be seen on the scan. This information will show your
radiation oncologist where to direct the radiation.
After the treatment sites are set, your skin will be
marked for treatment sessions. Your skin will be
marked with a felt pen. Sometimes, set-up marks are
made with tiny permanent tattoos. Photos of your set
up are taken. The marks and photos will be used to
position you for daily treatment sessions.
External beam radiation therapy
Radiation therapy is often delivered from a
large machine called a linear accelerator. The
rays pass through skin and travel to the tumor.
Healthy tissue is protected using modern types