Importance of Colon Cancer Screening

You are approaching 50 or have already reached or passed that age. You realize that you are due for Colorectal Cancer (CRC) Screening and that dreaded procedure you’ve heard so much about from family, friends and the media. You admittedly avoid seeing your Primary Care Physician (PCP) for fear of hearing him or her recommend testing, just as you might try to avoid driving Bay Area freeways during rush hour.

While CRC is the second leading cause of cancer death in the United States and despite the fact that with screening this cancer is often entirely preventable, many people are averse to testing due to its “unpleasantness.” The following discussion hopefully will demystify the options for CRC Screening and convince you that it is worth the “trouble.” Rest assured that most will have normal tests. According to the National Institute of Health (NIH) surveillance data 4.4% of adults across their lifespan will be diagnosed with CRC, meaning 95.6% will NOT.

Of note, this discussion assumes that you are at average or typical risk for CRC. There are some populations that should be screened from an earlier age and perhaps more frequently. For example, if you are African American, have inflammatory bowel disease, or have a strong family history of CRC or multiple other cancers. Be sure to tell your doctor if you have any risk factors that would warrant earlier or more frequent screening. In addition, if you have any gastrointestinal symptoms such as persistent pain, bloating, cramping or bleeding, etc. you need to let your doctor know immediately, regardless of your age. For more information on CRC screening guidelines go to the Centers for Disease Control and Prevention (CDC) website screening advice page.

“Help! How can I ease my anxiety about moving forward with this?”

For most people knowledge is reassuring, so read on. The purpose of screening is really twofold. Purpose #1 is that with proper screening cancer can actually be prevented. Yes, screening for this cancer can PREVENT it. How does that work? Isn’t testing about finding cancer? Well, yes and no. It turns out that most Colorectal Cancers begin in what are called Polyps which are often “Benign” (no cancer) or “Pre-malignant” (Pre-cancer but not cancer). By finding and removing Polyps, CRC can be prevented. (Now, THAT should be reassuring!) Purpose #2 is indeed to find cancer but while still in an earlier and more curable stage.

Now that you understand screening is good and worthwhile, you might ask yourself, “What next?” The next section explores the various screening tests in more detail. Whatever you decide to do, remember that consulting with your PCP is often tremendously reassuring and clarifying. These procedures sound intimidating, but talking through them with your PCP will shed more light on the risks and benefits. We understand that there is a natural hesitation to engage with your doctor particularly on this subject. However, at Carbon Health we make talking to a doctor easy. Our San Francisco office provides same-day, face-to-face appointments, and our doctors are also available via video calls and text chat through our app. Whichever way you would like to reach us, Carbon doctors are ready to discuss the options, so you can make informed decisions about your health that correspond to your values, concerns and desires.

“I’ve heard there are different ways of screening for colorectal cancer. How do I know what test I should have? Do I have to have a Colonoscopy?”

Congratulations, sounds as if you’ve acknowledged that some sort of screening might be an option for you. While a Colonoscopy is considered the gold standard in CRC Screening and is the preferred screening method in the US, you may be surprised to learn that there are less invasive screening tests available and because they are less invasive, they may be more acceptable to you, too. If there is a test that you are more willing to do because it is less intimidating, go ahead and do it! We have a lot of supporting evidence that a less thorough test is better than no test at all. These less invasive methods include Flexible Signoidoscopy (FS), Fecal Immunochemical Test (FIT) which has replaced the old Fecal Occult Blood Test (FOBT), and Cologuard, a DNA test of your feces. These tests have been shown to reduce the prevalence of colon cancer and the number of deaths associated with it. Although most doctors would recommend a Colonoscopy or FS, if you’re squeamish about a tube in your bottom, please do go ahead and start with one of the feces tests. While Colonoscopy, FS and FIT are all fully covered benefits as cancer screening tests under the Affordable Care Act (ACA or Obamacare), DNA/Cologuard may not be covered by your insurance. Carbon can help you to understand the potential procedure costs based on your individual situation.

“Gee, so what’s the difference between a Colonoscopy and a Flexible Sigmoidoscopy, and why should I select one over the other?”

As they say, the devil is in the details, so here goes. Colonoscopy is the most “thorough” screening test and is, again, considered the gold standard to which other tests are compared for their accuracy (sensitivity and specificity) and safety. It requires an extensive prep that some people find objectionable (but doable, and for most people worth doing to save their life). It is a procedure performed by an experienced gastroenterologist (the doctors who perform the Colonoscopies) in a procedure suite after conscious sedation is induced through an Intravenous (IV). During conscious sedation you are deeply sedated and relaxed but may be sufficiently awake to faintly perceive conversation and activity in the room. The doctor introduces the scope (a thin tube with camera and light source) into the rectum and advances it to the cecum, which is the beginning of the large bowel. As she advances the scope, air is introduced into the colon to open up the space (lumen). This air might produce a minor gas cramp, but odds are you won’t feel a thing throughout the entire procedure. As she removes the scope, she thoroughly inspects the lining of the bowel for lesions or polyps (lumps and bumps that don’t belong there), and if there is an abnormality, she may take a biopsy (remove a pinch of tissue for examination under a microscope) which you would not feel. When the procedure is completed, you spend about a half hour recovering from the sedation. After recovery you are done and ready for your ride home to rest for the remainder of the day. If all is clear, your next screening is not for another 10 years! The American Cancer Society (ACS) provides a more detailed explanation of the procedure overall.

Flexible Sigmoidoscopy (FS) is similar to a Colonoscopy, but only looks at the final third of your colon (the third closest to the rectum, or “left side” of the colon). It is a quicker procedure, requires less prep, is not done under any sedation, and you can drive to and from the appointment. As with the Colonoscopy, by finding and removing pre-malignant growths (polyps) this procedure can prevent cancer and save lives (including yours). Older traditional studies of large populations have found that this test reduces the number of deaths from CRC to the same degree as a Colonoscopy. This can be a little confusing, but the theory is based on the observation that 2/3 to 3/4 of cancers exist within the reach of the sigmoidoscope. If a polyp or cancer is found during an FS, a follow-up Colonoscopy is ordinarily undertaken at a later date to explore the rest of the colon. After a normal FS, you will be invited back for a repeat in 5 years (remember with a Colonoscopy you’re good for 10 years).

“If studies show that FS has similar outcomes as Colonoscopy, why bother with colonoscopy?”

It turns out that the polyps on the “right side” of the colon (reachable with the colonoscope) appear different (and may have different behaviors) from conventional polyps seen on the “left side” reachable via sigmoidoscope. A condition referred to as serrated sessile polyp/adenoma more commonly occurs on the “right side” of the colon. Previously this condition was less well understood, less well seen (because they’re flatter) and therefore more easily missed. There was even controversy around its potential pre-malignancy. Today gastroenterologists are thoroughly aware of these pre-malignant lesions and hunt very carefully for them. Latest research shows reduced number of deaths with Colonoscopy compared to FS.

“Hmmm, so why have a FS when a Colonoscopy is more thorough? “

Some people will prefer the FS because it is less invasive with lower risk of complications and 2/3 to 3/4 of polyps and cancers are within reach of the sigmoidoscope. The prep is easier, there is no anesthesia used and you miss less work. However, if benign or malignant polyps are found during an FS, a follow-up Colonoscopy will be recommended.

“There is absolutely no way anyone can convince me to undergo having a tube up my bottom!”

Ok, so you’ve discussed the options with your Primary Care Provider (or maybe not), and you’ve decided that FS and Colonoscopy are simply too invasive for your well-thought out, deeply held sensibilities. We understand that. Here are other options:

A third acceptable and standard screening method is a simple lab testing of the feces which you collect at home using a kit (FIT) to test for hidden blood in the feces. Cancers of the lower intestinal tract cause a rough surface that oozes tiny amounts of blood which the FIT will detect. If for any reason you are reluctant to undergo Colonoscopy or FS, the FIT is a reasonable approach. The upside of FIT is that it is performed by you in the privacy of your home, takes virtually no time, requires no prep, requires no anesthesia, and has no complications. FIT screens for cancer but is not as sensitive a test as Colonoscopy or FS, and it does not detect small pre-malignant conditions the way Colonoscopy and FS do, ie, it does not prevent cancer as well as Colonoscopy or FS. And if your FIT is positive (abnormal), a follow-up Colonoscopy will be recommended. To be truly effective in screening, FIT needs to be done on a yearly basis, so be prepared to be nagged every year to get this done. DNA testing of the stool is equally sensitive if not more than the FIT, but it is less specific. That means DNA testing is more likely to result in an abnormal result when none are truly present (absence confirmed by Colonoscopy). This is called a false positive. The effective frequency of a DNA/Cologuard test has not been determined, but the current recommendation is every 1–3 years.

In summary

Colonoscopy is the most thorough test and, if normal, is only done every 10 years. The downsides are the unpalatable prep, use of anesthesia, longer downtime from procedure and recovery, and slight risk of complications such as perforation and bleeding.

The FS is not quite as thorough as a Colonoscopy, but has the advantages of using no anesthesia, minimal prep and downtime and a lower risk of complications. It needs to be done every 5 years instead of every 10.

The advantages of the FIT is that it is the least invasive and has zero complications — if the results are normal, and does not require follow-up testing. The downside is that to be effective it is done every year until age 75 (or older).

The DNA/Cologuard is promising, but is expensive (>$600) and may not be covered by insurance. It is more sensitive than the FIT and picks up more abnormalities, but is less specific, meaning some of those abnormalities are not true (higher false positive rates), so you might end up with a Colonoscopy to follow-up. The frequency of DNA/Cologuard testing has not been determined but is anywhere from 1–3 years.

Checking out the USPSTF Final Recommendation Statement in table form may be helpful.

I hope I’ve been able to demystify and familiarize you with CRC screening options and how it is not as intimidating as one might imagine. Cancer is not a laughing matter, but it is true that a (fairly) simple screening test can save your life.

So jump onto BART or Muni, fasten your metaphorical seatbelt and head on over to see your doctor! Set up a video call or simply text chat her to start a conversation on your CRC screening. At the risk of sounding sensationalistic, your action could save your life.

(With Carbon Health, you can see a doctor today in person or chat with one virtually by downloading the smartphone application, following the simple onboarding and scheduling an appointment!)

Links to Selected References from the Peer-Reviewed Medical Literature:

Screening for Colorectal Cancer: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force. AULin JS, Piper MA, Perdue LA, Rutter CM, Webber EM, O’Connor E, Smith N, Whitlock EP SOJAMA. 2016 Jun;315(23):2576–94

CRC Facts and Figures 2014–2016 American Cancer Society

Evidence for colorectal cancer screening. Bretthauer M. Best Pract Res Clin Gastroenterol. 2010.

Norwegian Study : Four randomized trials have investigated the effect of guaiac-based fecal occult blood screening on CRC mortality, with a combined CRC mortality risk reduction of 15–17% in an intention-to-screen analysis, and 25% for those people who attended screening. Flexible sigmoidoscopy screening has been evaluated in three randomized trials. The observed reduction in CRC incidence varied between 23 and 80%, and between 27 and 67% for CRC mortality, respectively (intention-to-screen analyses) in the trials with long follow-up time. No randomized trials exist in other CRC screening tools, included colonoscopy screening. Conclusion: FOBT and flexible sigmoidoscopy are the two CRC screening methods which have been tested in randomized trials and shown to reduce CRC mortality. These tests can be recommended for CRC screening.

Multitarget stool DNA testing for colorectal-cancer screening. N Engl J Med. 2014;370(14):1987–97. Imperiale TF, Ransohoff DF, Itzkowitz SH, et al.

Conclusion: A stool test combining altered human DNA and fecal hemoglobin showed higher single-application sensitivity than a commercial FIT for both colorectal cancer and advanced precancerous lesions, although with lower specificity.

Protection from colorectal cancer after colonoscopy: a population-based, case-control study. Ann Intern Med. 2011 Jan 4;154(1):22–30 Brenner H1, Chang-Claude J, Seiler CM, Rickert A, Hoffmeister M.

German study. RESULTS: Overall, colonoscopy in the preceding 10 years was associated with 77% lower risk for CRC. Adjusted odds ratios for any CRC, right-sided CRC, and left-sided CRC were 0.23 (95% CI, 0.19 to 0.27), 0.44 (CI, 0.35 to 0.55), and 0.16 (CI, 0.12 to 0.20), respectively. Strong risk reduction was observed for all cancer stages and all ages, except for right-sided cancer in persons aged 50 to 59 years. Risk reduction increased over the years in both the right and the left colon. Colonoscopy reduced mortality from left-sided lesions but not right-sided lesions in persons 50–59 in this study.

Effect of flexible sigmoidoscopy screening on colorectal cancer incidence and mortality: a randomized clinical trial JAMA 312:606–615, 2014

Norwegian Pop Study. In Norway, once-only flexible sigmoidoscopy screening or flexible sigmoidoscopy and FOBT reduced colorectal cancer incidence and mortality on a population level compared with no screening. Screening was effective both in the 50- to 54-year and the 55- to 64-year age groups.

Once-only flexible sigmoidoscopy screening in prevention of colorectal cancer: a multicentre randomised controlled trial. Lancet 375:1624–1633, 2010

British Population Study published in Lancer used 1 x FS screening ages 50–64. Reduction in mortality 30%. Conclusion: Flexible sigmoidoscopy is a safe and practical test and, when offered only once between ages 55 and 64 years, confers a substantial and long lasting benefit.

Once-only sigmoidoscopy in colorectal cancer screening: follow-up findings of the Italian Randomized Controlled Trial — SCORE. J Natl Cancer Inst 103:1310–1322, 2011

Italian Pop Study showed a single flexible sigmoidoscopy screening between ages 55 and 64 years was associated with a substantial reduction of CRC incidence and mortality.

Protection from colorectal cancer after colonoscopy: a population-based, case-control study. Ann Intern Med. 2011 Jan 4;154(1):22–30. Brenner H, et al.

German Study: Colonoscopy with polypectomy can be associated with strongly reduced risk for CRC in the population setting. Aside from strong risk reduction with respect to left-sided CRC, risk reduction of more than 50% was also seen for right-sided colon cancer.

Colorectal-cancer incidence and mortality with screening flexible sigmoidoscopy N Engl J Med 366:2345–2357, 2012

Significant decrease in colorectal-cancer incidence (in both the distal and proximal colon. Mortality from Distal CRC was reduced by 50%.