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22

NCCN Guidelines for Patients

®

:

Rectal Cancer, Version 1.2017

absence of Lynch syndrome. They are found in about

15 out of every 100 rectal cancers (15%) without

Lynch syndrome.

Testing for loss of MMR proteins or MSI is advised

for all people with colon or rectal cancer. These

features may affect your treatment plan. There are

two tests that can be done.

PCR (

p

olymerase

c

hain

r

eaction) is a test that can

assess for MSI. The test consists of a process in

which millions of copies of a DNA part are made.

The copies will be examined for 5 MSI markers.

Tumors can be rated as MSS (

m

icro

s

atellite-

s

table),

MSI-L (

m

icro

s

atellite

i

nstability-

l

ow), and MSI-H

(

m

icro

s

atellite

i

nstability-

h

igh). MSI-H is defined

as the presence of 2 or more MSI markers. MSI-H

suggests dMMR but more testing is needed to

confirm.

An IHC (

i

mmuno

h

isto

c

hemistry) panel is used

to assess MMR proteins. It involves applying a

chemical marker to cells then looking at them with a

microscope. There are four types of MMR proteins.

They are MLH1, MSH2, MSH6, and PMS2. If all are

present, it is unlikely that any MMR gene is mutated.

If the MLH1 protein is missing, more testing should

follow. The cancer may be tested for a BRAF V600E

mutation or a modified MLH1 gene. If a BRAF

mutation or modified gene is present, you don’t have

Lynch syndrome. If not present or the other MMR

proteins are missing, the cancer will be tested for

MMR mutations to confirm Lynch syndrome.

Review

†

†

A medical history is a report of all health events

in your lifetime. It will include questions about

your family’s health to help assess if you have

a syndrome related to rectal cancer. Such

syndromes include Lynch syndrome and FAP.

†

†

Your doctor will examine your body for signs of

disease. He or she will touch parts of your body

to see if anything feels abnormal.

†

†

Blood tests may be done to look for signs of

cancer spread to distant sites.

†

†

Imaging tests allow your doctor to see how far

the cancer has spread without cutting into your

body.

†

†

A biopsy is advised when surgery is an option.

A needle biopsy may be done to test for cancer

in distant sites.

†

†

Molecular testing for MSI or missing MMR

proteins is advised for all rectal cancers. Testing

for mutated

KRAS

,

NRAS

, and

BRAF

genes is

advised for metastatic cancer.

2

Treatment planning

Review