Colon Cancer Screening: What Are the Options?

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Colon cancer is currently one of the most common cancers in the United States, superseded only by breast, lung, and prostate cancer. (1) Screening is crucial for helping doctors detect colon cancer in its early stages, when it is more treatable. However, there is significant controversy over what constitutes the best colon cancer screening method, and research shows that doctors are failing to provide their patients with balanced information about all the screening options, thus preventing patients from making informed decisions. (2) Read on to learn about the pros and cons of the available colon cancer screening methods and how you can help your patients determine the best screening type for their unique needs.

Current Colon Cancer Screening Methods

The purpose of colon cancer screening is to detect early-stage colon cancer and precancerous lesions in asymptomatic people before cancer develops or when it is still highly treatable. (3) The U.S. Preventive Services Task Force (USPSTF), a panel of national experts in disease prevention and evidence-based medicine, recommends that people at average risk for colon cancer commence screening at 50 years of age. Screening should continue until age 75, after which patients and their healthcare providers can decide whether to continue screening based on factors such as life expectancy, health status, and prior screening results. (4) The USPSTF endorses multiple methods for colon cancer screening. These methods include colonoscopy, the high-sensitivity fecal occult blood test (FOBT)/fecal immunohistochemical test (FIT), the stool DNA test, flexible sigmoidoscopy, and CT colonography.


Colonoscopy is an endoscopic examination of the large intestine in which a long, flexible scope is inserted through the anus into the rectum and colon, where it is used to capture images of the entire lining of the colon. If abnormal growths are seen during the procedure, the doctor can take a biopsy or snip off the growths using a tool attached to the endoscope. It is recommended that this procedure be performed every 10 years.

High-Sensitivity Fecal Occult Blood Test and Fecal Immunohistochemical Test (FIT)

Both polyps, which are abnormal growths of tissue projecting from the colon wall, and colon cancers can bleed; FOBT and FIT detect tiny amounts of blood in the stool and can indicate the presence of precancerous or cancerous lesions. This test requires a stool sample and is performed annually.

Colonoscopy is not the only option for #coloncancer screening. Gut microbial analysis may be the future.

Stool DNA test

Like FOBT and FIT, the stool DNA test detects tiny amounts of blood in stool that may signify cancerous lesions; however, it also detects 21 genetic mutations associated with the pathogenesis of colon cancer. When used as a sole source of screening, it is recommended that this test is performed every three years.

Flexible Sigmoidoscopy

As with colonoscopy, flexible sigmoidoscopy involves the insertion of an endoscope through the anus into the rectum and colon. However, it only visualizes the left side of the large intestine, the sigmoid colon, rather than the entire colon. When used as the sole testing modality, flexible sigmoidoscopy should be performed every five years.

CT Colonography

CT colonography, also referred to as “virtual colonoscopy,” uses x-ray equipment to obtain a series of pictures of the colon. A computer then assembles the pictures into a detailed image of the entire colon.

The Pros and Cons of Colon Cancer Screening Methods

Even though it is not the only way to screen for colon cancer, colonoscopy has become the default screening test ordered by many physicians. Concerningly, research indicates that doctors are failing to provide their patients with balanced information about the full range of screening methods available. In an observational study of audiotaped clinic visits between patients and their providers, it was found that doctors failed to discuss critical aspects of colon cancer screening, such as the pros and cons of all available screening methods, with their patients. (5) As healthcare providers, we need to inform our patients about the different types of colon cancer screening, not just colonoscopy, so that they can make informed decisions about screening and take charge of their own health. 



  • Colonoscopy visualizes the inner lining of the entire colon.
  • A biopsy can be performed if abnormal growths are detected.


  • Full cleansing of the colon is required.
  • Diet and medications need to be adjusted before the test.
  • Sedation is needed during the procedure.
  • Colonoscopy may not detect small polyps or flat lesions and cancers.
  • Colonoscopy is expensive—the average colonoscopy cost is $3,081—for those with insurance plans that do not cover the cost of screening. For those with plans that cover colonoscopy, deductibles range from zero to over $1,000. (6) While the Affordable Care Act requires coverage of colon cancer screening tests, plans that started before September 23, 2010, may have varying coverage requirements. (7)
  • Endoscopes are not single-use or disposable; they are used repeatedly. Bacteria form biofilms on endoscopes, increasing the potential for cross-contamination of fecal matter and tissue. (8)
  • Colonoscopies lead to “serious medical complications,” including colonic perforation and bleeding, in five out of every 1,000 patients. (9)
  • Doctors receive financial kickbacks for referring patients for colonoscopies. This may bias their decision to inform their patients about other colon cancer screening methods.



  • No cleansing of the colon or dietary restrictions are required prior to the test.
  • FOBT and FIT are non-invasive. The tests only require a stool sample, which can be collected at home and poses no risk of damage to the colon.
  • FOBT and FIT are inexpensive. The cost of the test ranges from $3 to $40. (10)
  • Multiple randomized, controlled clinical trials have found that annual and biennial FOBT screening significantly reduces the incidence and rate of death from colorectal cancer. (11, 12, 13) The reduction in incidence and mortality is the result of earlier detection and surgical removal of malignant colorectal tumors and premalignant adenomatous polyps.


  • False-positive results are possible with both FOBT and FIT.
  • The sensitivity of FOBT is higher for larger polyps, which are more likely to bleed, so it may miss smaller polyps. (14)

Stool DNA Test


  • In adults at average risk for colon cancer, the stool DNA test was found to be more sensitive than the FIT test. (15)
  • No cleansing of the colon or dietary restrictions are required.
  • The stool sample can be collected at home and there is no risk of damage to the colon.
  • The stool DNA test is lower in cost than colonoscopy. The cost ranges from $400 to $800.


  • The stool DNA test is higher in cost than FOBT/FIT.
  • Sensitivity for adenomas is low.
  • False-positive results are possible.



  • Minimal cleansing of the colon is required.
  • When performed just once between the ages of 55 and 64, flexible sigmoidoscopy significantly reduces the incidence and mortality from colorectal cancer. (16)
  • Complications are rare.
  • A biopsy can be performed if abnormalities are detected during the procedure.


  • Medication and diet changes may be needed before the test.
  • Sigmoidoscopy can’t detect problems in the upper portion of the colon.
  • The test is invasive and there is a small risk of bleeding, perforation, or tear of the colon.

CT Colonography


  • CT colonoscopy is less invasive than a standard colonoscopy.
  • No sedation is required.


  • The test exposes the body to ionizing radiation, which is an established cause of cancer. (17)
  • It requires a thorough bowel prep, equivalent to that needed for standard colonoscopy.
  • CT colonography carries a small risk of bowel perforation because a small tube must be inserted into the rectum to inflate it with air before x-ray images are taken.
  • CT colonography may miss up to 10 percent of large colorectal adenomas and cancers (lesions greater than or equal to 10 millimeters in diameter). The sensitivity of CT colonography is even lower for lesions smaller than 10 millimeters in diameter. (18)
  • If a lesion is seen, standard colonoscopy is still required. Approximately 8 percent of patients end up having to go through both CT colonography and standard colonoscopy. (19)

When guiding your patient through the decision-making process, these are some factors that should be considered: (20)  

  • The patient’s age, medical history, family history, and general health
  • Potential harms of the test
  • Preparation required for the test
  • Whether sedation is needed
  • Follow-up care
  • Convenience of test
  • The cost of the test and whether it is covered by insurance

Bacteria: The Future of Colon Cancer Screening?

Fascinating new research indicates that gut bacteria may play a pivotal role in the development of colon cancer. Scientists have found that two types of bacteria commonly found in the gut, Bacteroides fragilis and E. coli, can penetrate the protective mucus shield lining the colon, colonize the intestinal lining, and release toxins that provoke DNA damage and oxidative stress. The inflammatory environment created by these bacteria thus supports the growth of tumors. (21) Another type of gut bacteria, Fusobacterium nucleatum, has also been implicated in the development of colon cancer and has even been found in colon tumors. (22) These findings are significant because they indicate that gut microbial analysis may be a valuable screening tool in the future for assessing the risk of colon cancer. If microbes associated with colon cancer are detected in such an analysis, more frequent screening and the implementation of other preventive measures, such as dietary changes and balancing of the gut microbiome, may be warranted to reduce the risk of colon cancer.


  1. I am wondering if there are genetic patterns that play a role in colon cancer.

  2. Good analysis. One other negative of the CT colonography is the significant discomfort during (and hours after) the procedure, due to the volume of air pumped into the intestines.

  3. I live in Spain, where they have just added a blood test to the national health system here, currently for men only but they will add women later. According to reports, it is a type of “liquid biopsy.” During the procedure, a health care professional collects a routine sample of blood that is then analyzed with a blood assay called CMx to see if there are circulating tumor cells (CTCs). The accuracy of the blood test was calculated to be 84%-88%, higher than that of a standard FOBT. The chance for a “false positive” test result was less than 3%, according to the study. “False positive” means that the test results incorrectly showed signs of CTCs in a person without colorectal cancer. The lead study author for the test was Wen-Sy Tsai, MD, Linkou Chang Gung Memorial Hospital, Taipei, Taiwan. I’m curious as to what you think – I’m about to shell out 250 euros to do it (I’m female, so don’t get it for free), just to avoid the invasive colonoscopy. I had one several years ago, they did find polyps, but I never did it again as it messed up my digestion for a long time.

    • People with a history of previous colon polyps require colonoscopic surveillance. The timing of follow up colonoscopy depends on the number, size and histopatholgy results of the polyp(s). Your physician would have made a recommendation to you at the time of your last colonoscopy.

      A screening test for colon cancer is generally for people aged 50 years and older, who are asymptomatic, and are otherwise at average risk of developing colon cancer.

      People with a history of colon cancer or colon polyps, history of inflammatory bowel disease or family history of colon cancer are not average risk. People with higher than average risk for colon cancer should have a discussion with their physician to individualise further assessment.

      Likewise, people with certain GI symptoms should have a discussion with their physician or health care provider to see whether further testing is required. Symptoms such as rectal bleeding, recent change in bowel habit, new onset abdominal pain or unexplained weight loss typical require referral to a gastroenterologist.

      If you decide to repeat your colonoscopy, then you should discuss previous adverse reactions with your physician. They may consider changing the type of bowel preparation, use of CO2 gas during the colonoscopy or may even suggest a probiotic.

      Patients receiving a probiotic combination of L. acidophilus NCFM and B. lactis Bi-07 (1.25 × 10^10 CFU/day per strain) reduced the average duration of post-colonoscopy pain by a mean difference of 0.79 days (p=0.032) when compared with placebo. It didn’t help with bloating or altered bowel habit. ([D’Souza et al, 2015]. Randomized controlled trial of probiotics after colonoscopy. ANZ J Surg. 2017 Sep;87(9). )

      Hope that helps!

  4. Hi there Chris,
    Sadly I’ve suffered from colitis for over twenty years and have had a handful of colonoscopies. Each one a nightmare.

    What I wanted to share was that just the other night I watched a show called, The Nature of Things, The Power of Poo. The Nature of Things is a long running Canadian science show on CBC. I’m a Canadian eh. Anyway, it showed a doctor using a camera pill that the patient swallowed. It recorded pictures of the entire digestive tract. It was pretty amazing film and showed good detail. They didn’t mention if the patient had to do any cleanse prior but it sure looked like a simpler, less invaisive way to investigate the digestive tract.

    For me, I’d have to be on my death bed or knocked out totally unconscious before getting another colonoscopy but this camera pill I would try. I will also talk to my doctor about the other methods you mentioned. Thanks for the info!


    • Geoff,

      Screening tests for colon cancer are generally for asymptomatic people with average risk of colon cancer over the age of 50. Unfortunately having colitis increases your chance of developing colon cancer.

      People with a longstanding history of colitis generally require regular colonoscopy. Not only will a colonoscopy allow careful examination of the colon, it also allows biopsies to be taken to detect early cancerous changes. This should be discussed with your treating physician.

      Colon capsule endoscopy does not allow for biopsies to be taken. In addition, the colon capsule can’t manoeuvre around the colon or suction out fluid. As such, the bowel preparation for colon capsule endoscopy is typically more rigorous than for regular colonoscopy.

      Issues of sedation could also be discussed with your treating physician. In particular you can always ask what your options are and whether they use an anaesthesiologist.

  5. I recommend FOBT, annually for males over 50.y/o. I recommend a colonoscopy to males over 50 y/o with cancer risk factors and /or a positive FOBT

  6. Very interesting and informative. I’m 53 and had first colonoscopy at 50, I had 2 polyps removed that were precursors for adenoma. My grandmother had colon cancer and my mom also had adenomas. This is my first year on “Obamacare.” I have either a $4000 or $6500 deductible. I planned to get a colonoscopy but I had no idea it is so expensive. Tough to make a decision.

  7. Chris,

    What method do you recommend or would you choose for yourself?

    I’m a 45 year old male with no health problems who eats lots of vegetables. I was thinking the FOBT or Fit might be the way to go for me.


  8. Hello. I am not a doctor or medical professional of any kind, but I am the daughter of a man who is a colon cancer survivor thanks to discovery through colonoscopy at age 52. I have had the same procedure done on me since turning 50 and subsequently every 5 years. They found and removed 3 small polyps during my last test. I am now 69. I hate the darn test, or I should say the prep for it, and would welcome an effective alternative. My health provider is Kaiser.

  9. I really enjoy all your latest information. I am a Canadian citizen and look forward to getting another email with up to date health information. I am 74 years Old and followed a ketogenic diet for the last year and a half and do my best to be as healthy as possible. Thanks for all your efforts in the health field. Priscilla J. Butler.”

  10. In our area, Southern California, colonoscopies are standard of care.
    I think the challenge is for those who have had prior polyps removed or a family history of colon cancer. The gastroenterologist won’t consider any other options once started on colonoscopy. A safe effective alternative is important as the risks are too high for the procedure itself and it’s effects on digestive system.