NCCN Guidelines for Patients
Colon Cancer, Version 1.2017
Some imaging tests use contrast. Contrast is a dye
that will be injected into your bloodstream. It makes
the pictures clearer. Some people have an allergic
reaction to the dye. Tell your doctor if you’ve had
problems with contrast in the past.
CT with contrast
omography) takes many pictures of
a body part using x-rays. A computer combines the
x-rays to make one detailed picture. The picture is
saved for later viewing by the radiologist.
CT is advised if the cancer has spread beyond the
second layer of your colon wall. Get scans of your
chest, abdomen, and pelvis. Contrast should be
used. The radiologist will look for cancer in nearby
and distant sites.
During the scan, you will need to lie face up on a
table. The table will move through the machine. As
the machine takes pictures, you may hear buzzing,
clicking, or whirring sounds.
You will be alone in the room during the test. In
a nearby room, the technician will operate the
machine. He or she will be able to see, hear, and
speak with you at all times. One scan is completed in
about 30 seconds. You will likely be able to resume
your activities right away unless you took a sedative.
maging) uses a magnetic
field and radio waves to make pictures. It is not
often used to plan treatment for colon cancer.
Your doctor may order an MRI if the CT scan was
unclear. Contrast should be used. For stages II or
III, CT without contrast may also be done if you can’t
receive CT contrast.
Getting MRI is much like getting CT. Except, you will
need to wear a coil device. The device covers your
body from below your chest to the top of your legs.
It sends and receives radio waves. Straps may be
used to help you stay in place. MRI may cause your
body to feel a bit warm.
Sometimes CT is combined with PET (
omography). When used together, they
are called a PET/CT scan. PET/CT scan is not often
used to plan treatment for colon cancer.
There are three reasons why you may have a
PET/CT scan. PET/CT can show how big a tumor
is if you have metastases. PET/CT can also find
metastases other than in the liver that would exclude
surgery. Last, PET/CT may be an option if you can’t
receive contrast dye for CT or MRI.
PET/CT may be done with one or two machines
depending on the cancer center. For PET, a sugar
radiotracer will first be injected into your body. The
radiotracer is detected with a special camera during
the scan. Cancer cells appear brighter than normal
cells because they use sugar more quickly. PET can
show even small amounts of cancer.
Samples of tissue or fluid can sometimes be
removed from the body with a needle. This procedure
is called a needle biopsy. The methods of obtaining
samples with a needle differ based on the body
site. If your doctor suspects metastases, a needle
biopsy may be done. The samples will be sent to a
pathologist for cancer testing.