Today we'll talk even further
about disorders of the large bowel.
So we'll start with the case.
A 49-year-old man is seen
in clinic for a routine visit.
He feels well with no symptoms.
He has a past medical history of hypertension,
and a 20-pack year smoking history.
His father was diagnosed
with colorectal cancer at age 58,
so he is worried about his
chances of having colon cancer.
He has heard there are
many types of screening tests
and is interested in the tests with
the best ability to rule out cancer.
His vitals are normal and
physical exam is unremarkable.
So which screening test for colorectal
cancer is the best recommendation for him?
Before we answer that, let's
identify some key points in this case.
In general, so he's 49, in general we begin
colorectal cancer screening usually at age 50.
However, he does have a first degree relative
with colorectal cancer diagnosed at age 58,
so we might consider screening a bit sooner.
How soon? We'll find out.
In addition, it is important to note, that he
asked for the test with the best sensitivity.
So here, as in with the real life patient, you
always want to ask what the patient desires
and try to determine which
test meets their needs best.
So, as we said earlier, in general we start
screening for colorectal cancer between age 50 to 75.
You might start sooner
depending on different risk factors,
how much sooner depends
on which guidelines you use.
So, some factors you might
use to help you decide are:
whether they have an
inflammatory bowel disease,
if they have a first-degree
relative with colorectal cancer
or an advanced adenoma that
was diagnosed before age 60,
whether they have a
familial cancer syndrome,
or African American race.
So some other major risk factors for colorectal
cancer include advanced age, generally over 50,
a personal history of adenomatous polyps,
inflammatory bowel disease,
a family history mostly a first
degree relative with colorecatal cancer,
and dietary factors also play a role.
So diet high in fat, high in red meat but low in fiber
can place you at high risk for colorectal cancer.
So let's talk now about the various types of screening
tests we have available for colorectal cancer
The first type of test is the
fecal occult blood test or an FOBT.
This is simply a small card on which a
patient can place a small stool sample
and then they can easily mail it in and
have it analyzed for the presence of occult blood.
You may also do a CT colonography.
This is a 3-dimensional
simulation of the colon,
so it's a CT that we do to then
get a look to the inside of the colon.
Lastly, you may also do a
sigmnoidoscopy or colonoscopy
which is really the most direct way to look at the
colon and be able to intervene at the same time.
So now let's compare and
contrast all of these variable tests.
These is one test called
the fecal immunochemical test or FIT test.
It is done very similarly to the
FOBT that we mentioned done before.
In general, it is done every year.
The advantage are that it is noninvasive
and it is very convenient for patients to do
since they are simply
mailing in a stool sample.
The disadvantage, unfortunately is that it
has a low sensitivity for detecting cancer.
An FOBT or fecal occult blood test is
very similar in that it's done annually.
It is also non-invasive and convenient
for patients but again, has low sensitivity.
Next, you could offer a CT colonography.
This is typically done every 5 years.
It is non-invasive since it's just a CT scan.
But, because it's just a CT scan, there's no
ability to intervene if you find something suspicious.
You might also consider sigmoidoscopy
This is usually done every 5 years.
It has excellent sensitivity for detecting
abnormalities but is limited only to the sigmoid colon.
In addition it is invasive,
it requires a bowel prep.
And as we mentioned, it really
only visualizes the sigmoid colon.
So it's a bit limited in its reach.
And then lastly, a colonoscopy.
It’s really the gold standard for screening, it
should be done every 10 years.
It has the highest
sensitivity, of all of these tests.
The disadvantages, are that it too
is invasive and requires a bowel prep.
As a quick aside,
you should always remember that if a patient does have FOBT
or a FIT test that turns out positive for occult blood,
they must then be referred for colonoscopy.
So now that we know that,
let’s go back to our case.
We have a 49-year-old man who is
asking about the best test to rule out cancer.
He does have a first-degree relative
with cancer diagnosed at age 58,
which might prompt you to
consider your screening sooner.
So, which screening test do we recommend for him?
Since he's at elevated risk for colorectal
cancer, with his first-degree relative,
you should consider
screening with a colonoscopy
since he's asking about the test
with the best ability to rule out cancer.
Colonoscopy has the highest sensitivity.