Colorectal Cancer (CRC) is the 3rd leading cause of cancer death in the US, accounting for 10% of all cancer deaths. The average American has a 5% lifetime risk of developing CRC. 1 in 3 people who develop CRC will eventually die from it (as opposed to 1 in 5 for breast cancer).

Although having a family member with colon cancer will increase your risk of also getting it, most new cases of CRC are in people without a previous family history. Other factors, such as cigarette smoking, diabetes, and certain bowel diseases may also increase your risk of developing CRC.

The most important risk factor of developing CRC is the presence of colonic polyps, which are an outgrowth of tissue, composed of glandular tissue (usually) that extend into the colon. The larger the colon polyp, the greater the risk of turning into CRC. Certain types of polyps, called tubular adenomas are associated with a very high risk of developing CRC.

An important fact to understand is that removing these polyps before they become cancer will eliminate their chance of turning cancerous.  What this means is that most colon cancer is entirely preventable. Remove the polyp before it becomes cancer; remove the risk of changing into cancer. This highlights the absolute importance of colon cancer screening. Colonoscopy is the only cancer screening test that can actually cure the disease before it occurs (as opposed to mammography, which just identifies the presence of cancer but does nothing to remove it).

Screening tests for CRC include:

1. Hemoccult testing of stool: Many doctors will test for hidden blood in the stool when a man gets a prostate exam or a woman gets a pap smear. While this is not bad to do, it is a very poor test to rule out colon cancer (Collins JF; Lieberman DA; Durbin TE; Weiss DG; Ann Intern Med 2005 Jan 18;142(2):81-5). Giving a test to do at home where at least 3 consecutive BM’s are tested is a more sensitive test for CRC, but still misses at least 60% of all Cancer. Still, doing this test will increase the chance of finding and curing cancer, and people who get this test done live longer than those who do not. It is just not a good idea to rely on this test alone when better tests are available to be used along with or in place of Hemoccult testing.
2. Flexible sigmoidoscopy: This is a flexible tube that looks at the last 60cm or so of the large intestine. It can be done in the doctor's office and so became a popular test to perform (by doctors, not necessarily patients). Studies have shown that doing these on a regular basis can reduce the risk of CRC by 1/3. This is clearly a better test than Hemoccult testing in that a high percent of cancers are in the last part of the colon, but it still misses cancers in the rest of the colon. Combining this test with the hemoccult test will do even better. Usually patients are not sedated during sigmoidoscopy.
3. Colonoscopy: A colonoscope is basically a longer sigmoidoscope. It looks at the entire colon and has the added advantage that it can remove any polyps that are present. In theory, a negative colonoscopy should eliminate the risk of developing colon cancer.  In reality, a small percentage of polyps are missed, but nearly all large polyps and cancerous areas are found and dealt with via colonoscopy. Since it is a riskier than sigmoidoscopy, the patient is generally sedated during the procedure.
4. Virtual Colonoscopy: This has gained a lot of attention from people (mainly as a means to avoid colonoscopy), but the optimism is probably misplaced. While the sensitivity of this procedure at picking up polyps or cancer is approaching that of colonoscopy, it requires the use of air contrast, which is probably less comfortable than the colonoscopy (and you don’t avoid the prep). It is also significantly more expensive. The advantage of this procedure is that it is safer than traditional colonoscopy. It has yet to be proven to be a viable alternative.

Who gets screened? If you are over age 50, you should start regular screening for CRC. For individuals with a strong family history or other risk factor, screening may begin at age 40. The choice of test depends on risk and other factors:

• If average risk, you should have hemoccult testing done every year
• The addition of sigmoidoscopy every 5 years will reduce the risk embarrassingly
• Another option is colonoscopy every 10 years instead of sigmoidoscopy - this is considered the best choice, but insurance coverage for colonoscopy is not always there.

What I tell my patients (the “Bottom Line” – pardon the pun):

• Get it done. We should not have many people dying from colon cancer since the majority of cases could be prevented.
• Get a colonoscopy done if your insurance company pays for it (Medicare will cover screening colonoscopy).  If not, sigmoidoscopy is a reasonable second choice.
• The worst part of Colonoscopy is the prep.  The night prior to getting your procedure you have to cleanse your bowels with a strong cathartic medication (although they have trended away from the "gallon jug" which was ironically-named "Go-Lytely").  They put you to sleep during the procedure itself, so most people don't remember getting it done.
• If you have an increase risk of developing colon cancer, getting tested earlier with a colonoscopy is preferred.