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March 15, 2003
Time for a Colonoscopy?
If you're over 50, it's time to get this important test.
By Scott C. Anderson
Dave Weis works as a branch manager for an industrial
wholesaler in Minnesota, but on his days off, you can find him on
the golf course. When he turned 50, he joined the professional senior
golf tour. Together with the James E. Olson Foundation (JEO), the
tour has been promoting colon cancer awareness for the last three
years. Dave learned that Olson, the former chairman of AT&T,
died from colorectal cancer a scant four weeks after his diagnosis.
That tragic story, along with his doctor’s recommendation, was all
the provocation he needed: he signed up for a colonoscopy.
Good thing, too. The colonoscopy revealed three polyps
the size of a pencil eraser, which were removed by his gastroenterologist.
Dave says, “I'm really glad I did it. The doctor said the polyps
could grow into cancer. It’s frightening to think of
what would have happened if I hadn’t found the courage to get the
procedure.”
Colorectal cancer, also called colon cancer, is the
second most deadly cancer in America. This year, there will be about
150,000 new cases diagnosed. Out of those, there will be almost
60,000 deaths. Despite this horrible toll, colorectal cancer is
still “the cancer no one wants to talk about.” And that’s a shame,
because a colonoscopy, like the one Dave got, can save your life.
Fewer than 40% of the people who need it are getting
screened for colon cancer. People are uncomfortable even talking
about it. We are, as a nation, dying of embarrassment.
Spotted early, colon cancer is one of the most curable
cancers known. Over 90% of patients who are diagnosed early can
be cured, but those odds flip if you wait too long and the cancer
becomes established. Fewer than 10% of that group will survive for
five years. With those odds – and all the tests that are available
– you really have no excuse!
What is colon cancer?
Like most cancers, colon cancer results from an accumulation
of genetic mistakes. One of the mistakes is the loss of tumor suppressor
genes – genes that protect against cancer. Another mistakes is the
mutation of a gene into a cancer gene. Together with some other
mutations, the affected cells finally succumb to cancer. At that
point, they no longer perform their normal function, and they begin
to grow out of control. If these growths aren’t removed, they can
become metastatic, invading other tissues in the body.
Colon cancer can take 5 to 15 years to develop, and
that’s why early detection can be so beneficial – the cancer can
be nipped in the bud.
What are the symptoms?
Early stage colon cancer basically has no noticeable
symptoms. That’s another reason to get screened. By the time symptoms
show up, like blood in the stool, the cancer may already be advanced.
That’s another good reason to get regular screenings.
How to check for colon cancer
There are several tests for colorectal cancer:
Fecal Occult Blood Test (FOBT): The fecal occult
blood test, or FOBT, is designed to find blood in your stool that
could indicate a bleeding polyp. New home kits are easy to use:
you simply toss a flushable card in the toilet and note the color.
Although this test is simple and painless, it is also
error-prone. There may be more than one reason for you to have blood
in your stool, such as hemorrhoids. That produces a false positive
result. In addition, polyps don’t always bleed, so you may get a
false negative as well. That’s one reason that the American Cancer
Society recommends taking the FOBT along with a sigmoidoscopy.
Sigmoidoscopy: This is fairly simple procedure
usually done in your doctor’s office. The sigmoidoscope has a fiber
optic bundle or a tiny camera that lets the doctor see the inside
of the colon. It also has tubes to deliver air and water and a suction
tube to capture tissue for biopsies. The sigmoidoscope is only long
enough to inspect the last third of the colon, called the sigmoid
in honor of its “S” shape. That means it can miss up to 25% of potentially
cancerous polyps.
Colonoscopy: This uses a longer version of
the sigmoidoscope that can inspect the entire colon. This is the
“gold standard” for colon cancer testing, and some physicians, such
as David Lieberman, MD, Chief of Gastroenterology at Oregon Health
Sciences University in Portland recommend colonoscopy as a first
line of defense. Medicare now covers colonoscopies for patients
over 50. Colonoscopies must be performed by a gastroenterologist
or a colorectal surgeon. Due to the growing awareness of colonoscopy’s
benefits, there are not enough of these specialists to go around,
but be persistent.
Double Contrast Barium Enema: This procedure
outlines the colon with barium, so it can be visualized in an x-ray.
Virtual Colonoscopy: This non-invasive test
uses a CAT scan to produce a virtual, 3D image of the colon. No
scopes are needed, just a computer to “fly” through the virtual
model. The resolution is not as good as a standard colonoscopy,
but it’s improving. With the dearth of qualified colonoscopists,
this technique is becoming more popular.
Recommendations
Starting at age 50, The American Cancer Society recommends
the following schedule for these tests:
FOBT annually and flexible sigmoidoscopy every five years, or Flexible sigmoidoscopy every five years, or FOBT annually, or Colonoscopy every 10 years, or Double contrast barium enema every five years.
If
you have a heightened risk, either because you have Irritable Bowel
Syndrome, Crohn’s Disease or a genetic predisposition like Familial
Adenomatous Polyposis (FAP) or Hereditary Nonpolyposis Colon
Cancer (HNPCC), your doctor will set up a more aggressive schedule
for you.
Taking the test
So you’re convinced, you’ll get a colonoscopy. What
should you expect?
For your doctor to see what’s going on, you need a
squeaky-clean colon. It is universally agreed that this is the nastiest
part of the procedure. Starting the day before your appointment
you drink a foul-tasting liquid laxative, but some people prefer
a tasteless sodium phosphate pill called Visicol that is equally
effective.
On the day of the procedure, you will most likely
report to an outpatient office where an anesthesiologist will sedate
you slightly for the procedure. A gastroenterologist
or a colorectal surgeon will perform the colonoscopy. The
colonoscope has an air tube to puff up the colon for better viewing.
That will make you feel a little bloated, but don’t worry – it will
soon pass.
Typically, the procedure only takes about five minutes.
If any polyps are spotted during the colonoscopy,
they are cut out and collected for biopsy. In effect, this makes
a colonoscopy more than a screening – it is a treatment as well.
You may feel a little groggy afterward, so make sure
you have someone to drive you home.
How to prevent colon cancer
Now that you’ve set up a schedule with your doctor
for regular screenings, what else can you do to reduce your chances
of getting colon cancer? It turns out that preventive medicine is
a lot like your mother’s advice: get some exercise, quit smoking
and eat right. Eating right means lowering your fat intake and getting
lots of fruit and vegetables. Here are some other tips:
Lose weight: This may be the most important
advice, since obesity can double your odds of getting colon cancer.
Drink less: You don’t need to be a tea-totaller
(a glass of wine is good for your heart), but don’t overdo it. Fortunately,
both tea and coffee have been exonerated from causing cancer, and
green tea may even be beneficial (at least in mice).
Take an aspirin: Not just a recommendation
for heart disease, but for colon cancer as well. In fact, many Non-Steriodal
Anti-inflammatory Drugs (NSAIDs) can cut the risk in half through
their effect on a hormone pathway involving cyclooxygenase (COX).
Take your vitamins: Calcium is one of the most important
supplements you can add to your diet. 750 milligrams a day can cut
your risk in half. Vitamin D helps, since it clears the cancer-promoting
agent lithocolic acid from the colon. Be careful not to exceed 600
IU a day -- too much can cause side effects. If you don’t like pills,
you can also get some vitamin D by grabbing a little sun.
Try to get half a milligram of Folate a day, which
has been shown to slow polyp growth. About 400 IU of vitamin E has
been shown to be beneficial as well.
With all these supplements, make sure you talk to
your doctor first! If you already have cancer or are on certain
medications, these vitamins may be dangerous. But if your doctor
agrees, popping a couple of pills each day can dramatically improve
your odds.
How to treat colon cancer
A colonoscopy not only screens for cancer,
but by removing the polyps, it can cure it as well. However, if
the cancer is already established, surgery is called for. The cancerous
section of the bowel is cut out and then the rest of the colon is
stitched back together. But there are some other treatments that
have recently been approved or are in clinical trials:
Anti-angiogenesis factors: As tumors grow,
they secret substances that encourage the growth of new blood vessels.
This is called angiogenesis, and without it, tumors are stunted,
staying smaller than a pinhead. One of the most potent chemicals
that encourage blood vessel growth is called vascular
endothelial growth factor or VEGF. Various drugs, such as anti-VEGF
from Genentech and SU 5416, from Pharmacia, are currently undergoing trials. Although the
drugs are effective at stopping the growth of blood vessels, it’s
still too early to know if their potential side effects are tolerable.
Another potential
angiogenesis factor is cyclooxygenase-2 or COX-2. As noted above,
drugs as simple as aspirin can inhibit COX-2, helping to starve
and shrink tumors. Other drugs that block COX-2 include ibuprofen
and Celebrex, the arthritis drug. A new COX inhibitor currently
in trials, JTE-522, may also halt the spread of colon cancer
to other organs.
Oxaliplatin and CPT-11: Oxaliplatin, also called
Eloxatin, was approved by the FDA last August. Its efficacy was
high enough that the approval only took seven weeks, an extraordinarily
fast turnaround for the FDA. The drug is intended for late-stage
colon cancer as a part of a chemotherapy regimen. Patients who were
given Oxaliplatin lived months longer than those using different
chemotherapy cocktails.
A drug called CPT-11, trademarked as Camptosar, has
also been used in combination with Oxaliplatin. CPT-11 has been
shown to reduce tumor growth in about 80% of colorectal cancer patients.
These two new drugs promise to significantly improve the outlook
for late-stage colon cancer patients.
Keyhole Surgery: Colon tumors can be removed
with a laparoscope, a tiny camera that can be inserted through a
small incision (the “keyhole”) to monitor surgery. Tumors can be
removed with this technique with very little damage to the surrounding
tissues. Patients have less healing to deal with, so they can go
home earlier and expect fewer complications. Initial studies also
indicate that recurrence of the cancer is reduced by 60% with the
laparoscopic procedure.
Gene testing: A $200 blood test can determine
if you are at greater risk. It will soon possible to test the stool
for some of the genetic changes that lead to full-blown colon cancer.
Radioimmunoguided Surgery: This novel treatment
uses monoclonal antibodies (MAbs) that stick to cancer cells. The
MAbs are made slightly radioactive, and then a sensitive radiation
detector can home in on the cancer cells. This technique can find
cancer cells that CT scans and even surgical exploration may miss.
Immunotherapy: This technique, which is intended
to prevent re-occurrence of cancer, mixes irradiated cancer cells
with a weakened tuberculosis bacteria to make a vaccine. For those
patients who are sensitive to the vaccine, the survival rates climb
from 63% to 85%. Unfortunately, the vaccine isn’t helpful to other
patients.
Copyright © 2000-2004 by Scott Anderson
For reprint rights, email the author:
Scott_Anderson@ScienceForPeople.com
Here are some other suggested readings about colonoscopies:
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