NCCN Guidelines for Patients® | Colon Cancer - page 23

NCCN Guidelines for Patients
®
Colon Cancer, Version 1.2014
21
3
Treatment planning
Blood tests | Molecular testing
Blood tests
Blood tests are used to look for signs of disease. A
CBC (
c
omplete
b
lood
c
ount) measures the number
of white blood cells, red blood cells, and platelets.
Your blood counts may be low because the cancer
has spread into your bones, the cancer is causing
bleeding, or because of another health problem.
Another blood test is a chemistry profile. When colon
cancer spreads, it can cause high or low levels of
chemicals in the blood. One example is a high CEA
(
c
arcino
e
mbryonic
a
ntigen) level. CEA is normally low
in healthy adults unless a woman is pregnant. If not
pregnant or if you’re a man, high CEA levels suggest
the cancer has spread far.
Molecular testing
Abnormal genes aren’t always passed down from
parents to children. Instead, there can be non-
inherited changes in genes. Molecular testing
assesses for genes known to have an effect on
cancer treatment. Molecular testing is done with
tissue removed from the tumor. If you have stage IV
colon cancer, molecular testing of the following genes
is recommended.
RAS mutation
RAS is a family of proteins found in cells. Some colon
cancers have abnormal genes that control the RAS
proteins. As a result, the RAS proteins made by the
abnormal genes are overactive and promote cancer
cell growth. Some treatments for colon cancer do not
work if the genes that control KRAS and NRAS—
members of the RAS family—are abnormal.
BRAF mutation
If the
RAS
genes are normal, the
BRAF
gene may
be tested next. The protein made by the
BRAF
gene
is involved with signals within cells that trigger cell
growth. About 5 to 9 out of 100 colon cancers have
a mutated
BRAF
gene.
BRAF
testing is not used to
decide use of targeted therapy, which is discussed
in Part 4. Instead, it helps doctors decide prognosis.
Prognosis is the pattern and outcome of a disease
based on tests.
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