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by Dr. C.H. Weaver M.D. updated 5/2021

Colorectal cancer is the second-leading cause of cancer death in the United States. The American Cancer Society estimates that approximately 150,000 cases of colorectal cancer will be diagnosed this year and nearly 52,000 people will die from the disease.

But it doesn’t have to be that way. If more people underwent screening for colorectal cancer, we might see those numbers drastically decline. Unfortunately, it’s not that simple. Scheduling a colonoscopy falls pretty low on most people’s to-do list—just above having a root canal.

Colorectal Colon Rectal CancerConnect 490

“There is no question that currently our biggest obstacle in colorectal cancer is the underutilization of screening,” explains Steven Nurkin, MD, MS, assistant professor of oncology in the Department of Surgical Oncology at Roswell Park Cancer Institute. “Approximately 40% of the US population is not getting screened—even though we know that screening works.”

Colorectal cancer screening guidelines are designed to diagnose cancers in early, highly treatable stages or detect precancerous conditions before they progress, adhering to them is the first step toward a successful outcome for both men and women. The number of individuals skipping or delaying screening for colon cancer has increased significantly due to the COVID-19 pandemic. This is projected to result in significant excess mortality from colon cancer which would have otherwise been prevented. Individuals should discuss screening options with their physician as several can be accomplished without visiting the hospital and colonoscopy is not associated with additional COVID-19 related problems.

Results of a study published in the New England Journal of Medicine indicate that colonoscopy substantially reduces the risk of death from colorectal cancer.1

When it comes to colorectal cancer, screening is prevention.

Michele Cofield, a 68-year-old retired schoolteacher from Buffalo, New York, is what you might consider a rule follower. She wears her seatbelt every time she gets in the car, undergoes regular mammograms, eats a healthy diet, and even remembers to schedule her 10-year follow-up colonoscopy. And it’s a good thing too because last July that 10-year colonoscopy revealed a 4 centimeter tumor at the base of her large intestine. After a biopsy indicated that the tumor was malignant, she was diagnosed with Stage I colorectal cancer and underwent surgery at the Roswell Park Cancer Institute to remove it.

Michele was lucky. Thanks to routine screening colonoscopy, the cancer was found early before it had a chance to spread. “I am a success story for screening colonoscopy,” Michele insists. “I scheduled my colonoscopy on time. I was not expecting to find malignancy in my colon, but it was there and it had been for a while.”

The experience reinforced what Michele already knew: screening works. What’s more, there are some new advances in colorectal screening that may make it easier—and less invasive—to stay on top of screening.

Current screening guidelines for Colorectal cancer

Individuals who are 45 or older have different screening options for colorectal cancer, although a colonoscopy is the preferred method. There are five screening schedules based on the type of screening test as well as initial findings that indicate that no cancer or other serious conditions exist. If abnormal results are produced by any of these screening methods, a colonoscopy should follow.

  • Colonoscopy every 10 years. A colonoscopy includes the evaluation of the entire large intestine through a lighted camera that is inserted through the rectum. The image of the large intestine is shown on a screen so the physician can identify any abnormal-looking areas. A biopsy )sample of tissue) may be obtained during the colonoscopy to determine if cancer or other diseases exist.
  • Flexible sigmoidoscopy every five years. A sigmoidoscopy includes the evaluation of the lower portion of the large intestine. A lighted camera is inserted through the rectum so the physician can visually examine the area for abnormalities.
  • Fecal occult blood test (FOBT) or fecal immunochemical test (FIT) every year. FOBT and FIT tests can detect small amounts of blood or cellular changes in the stool that may be indicative of colorectal cancer. FOBT may be performed at home with a kit that is provided to patients.
  • FOBT or FIT test every year plus flexible sigmoidoscopy every five years. This combination method is preferred to either yearly FOBT/FIT or flexible sigmoidoscopy every five years.
  • Double-contrast barium enema every five years. An enema including barium contrast is given prior to an X-ray. The barium contrast allows the physician to visualize the colon on X-ray and detect any abnormalities.

What’s Your Risk of Developing Colon Cancer?

Average risk:

  • Age 45 or older
  • No history of colorectal cancer, precancerous polyps, or inflammatory bowel disease
  • No family history of colorectal cancer

Increased risk:

  • Personal history of colorectal cancer, inflammatory bowel disease, or polyps found during colonoscopy
  • Family history of colorectal cancer

High risk:

  • Family history of a hereditary syndrome associated with colorectal cancer
  • Personal history of 10 or more polyps
  • From a family that meets the Amsterdam II Criteria: Three or more relatives have colorectal, uterine, or another Lynch-associated cancer, one of whom is a first-degree relative of the others Two or more successive generations have cancer One or more relatives diagnosed before the age of 50 Familial adenomatous polyposis has been excluded
  • From a family that meets the Bethesda Guidelines:
  • One relative diagnosed with colorectal cancer prior to age 50
  • Presence of any synchronous (at the same time) or metachronous (at another time) Lynch-associated tumors, regardless of age
  • Colorectal cancer with high microsatellite instability histology diagnosed in a patient under the age of 60
  • Colorectal cancer diagnosed in one or more first-degree relatives with a Lynch-associated tumor, with one of those cancers diagnosed before age 50
  • Colorectal cancer diagnosed in two or more first- or second-degree relatives with Lynch-associated tumors, regardless of age

Screening Guidelines

Screening guidelines vary based on risk level and screening outcomes. In general, the screening interval decreases if anything is found during screening. Some data indicate that African Americans are at an increased risk of colorectal cancer and therefore should start screening at age 45 rather than 50, even if they are considered average-risk. The USPTF changed their recommendation to begin screening at age 45 in October 2020. National Comprehensive Cancer Network guidelines recommends beginning screening in average-risk individuals at age 50.

Average-risk guidelines:

  • Colonoscopy is the preferred method. A negative colonoscopy should be followed by a repeat test in 10 years.
  • Stool-based tests of sigmoidoscopy are other screening options but should be repeated every five years.

Increased-risk guidelines:

  • Begin screening at age 40 or 10 years earlier than the age of diagnosis of a first-degree relative.
  • Guidelines are very nuanced depending on the individual risk profile. Those with low-risk polyps are recommended to repeat colonoscopy screening every five years; those with high-risk polyps are recommended to repeat colonoscopy every three years; and those with incomplete polyp removal are recommended to repeat colonoscopy within two to six months.

High-risk guidelines:

  • High-risk individuals may need to start colonoscopy screening as early as age 20 or two to five years prior to the age of a family member in whom the earliest colorectal cancer has been diagnosed.
  • Colonoscopy screening should be repeated every one to two years.

Individuals with high-risk factors should discuss their own health history and family health history with their physician to determine their optimal individual screening schedule.

Screening Tests for Colorectal Cancer

Most people assume that screening for colorectal cancer means undergoing a colonoscopy, but there is a variety of screening tests for the disease. Dr. Nurkin explains that the screening tests are divided into two categories: structural tests and stool tests. Structural tests, such as colonoscopy and flexible sigmoidoscopy, are used to examine the colon and identify polyps. Stool tests, such as the fecal occult blood test, examine the stool for blood and cancerous cells (see “Screening Glossary” below).

The most common structural tests for colorectal screening are colonoscopy and flexible sigmoidoscopy. Colonoscopy allows physicians to view the entire colon, whereas flexible sigmoidoscopy allows visualization of only the lower part of the colon.

Although there are several different ways to screen for colorectal cancer, colonoscopy is the gold standard because it allows physicians to view the entire colon and remove polyps during the procedure. “No other screening method can do that,” Dr. Nurkin explains. “Any screening test is better than none, but colonoscopy is best.”

Some people prefer to have flexible sigmoidoscopy because it is less invasive, but Dr. Goldberg jokes that “having flexible sigmoidoscopy is sort of like getting a mammogram of only one breast because you’re looking at only part of the colon.”

Still, he says, “If the choice is between sigmoidoscopy and nothing, sigmoidoscopy is better than nothing.” In fact, a study published in the New England Journal of Medicine found that sigmoidoscopy screening can reduce the risk of developing colorectal cancer or dying from it—and it just might improve screening rates.2

Ironically, many of the less-invasive, easier screening tests lead to follow-up with colonoscopy screening anyway—so sometimes it makes sense to just do that in the first place.

What Is a Colonoscopy?

Screening colonoscopy can visualize the entire colon in more than 98% of individuals and studies consistently show that screening colonoscopy reduce the incidence and mortality from colon cancer. Compared with stool-based screening, colonoscopy has advantages, including a 10-year screening interval if bowel preparation is adequate and the examination shows no neoplasia, the ability to inspect the entire colon, and the ability to diagnose and treat lesions in the same session.3-10

A colonoscopy is a procedure in which a thin, flexible tube—or scope—with a built-in camera is placed through the patient’s rectum and physically advanced through the entire large intestine. The day prior to a colonoscopy, patients undergo a “bowel prep,” which may include laxatives and enemas. Immediately before the procedure, patients may receive relaxants or pain medication, although they tend to be awake throughout the test. When patients are fully prepped, air is placed into the colon as the tube advances so that the colon is expanded and the physician is able to view on a video monitor real-time pictures of all sides of the lining of the colon. The physician is able to identify areas that look suspicious for cancer or other diseases, and biopsies or the removal of polyps (small growths within the colon that can turn cancerous) may be performed during the procedure for laboratory examination. Patients are often groggy for a few hours following a colonoscopy and are not allowed to drive themselves home after the procedure.

What Is a Sigmoidoscopy?

A sigmoidoscopy uses the same general type of scope as in a colonoscopy, though it is much shorter and only exams the left side of the colon (about 40 percent of the total colonic length). The scope is inserted through the rectum and advanced through just the lower portion (approximately 2 feet) of the large intestine. Often a sigmoidoscopy is performed during an office visit; and although air is also placed into the colon as the scope is advanced, patients typically do not require sedation or pain medication. As with a colonoscopy, the physician is able to directly view the lower portion of the lining of the colon and remove suspicious areas, such as polyps. Although patients may be advised to take a laxative or an over-the-counter enema prior to a sigmoidoscopy, the bowel prep tends to be significantly less aggressive than that required for a colonoscopy, and patients are able to drive themselves home from their appointment. If polyps or suspicious areas are detected, patients are often referred to undergo a subsequent colonoscopy.

What is Fecal Occult Blood Testing FOBT?

Fecal occult blood testing FOBT uses an indirect enzymatic reaction to detect blood in the stool that may indicate the presence of colorectal cancer. If an FOBT result is positive (there is blood in the stool), a patient will often be referred for a subsequent colonoscopy. Screening with FOBT involves annual testing of 3 consecutively passed stools from different days. Dietary and medication restrictions before and during the testing period are critical, as red meat contains hemoglobin, and certain vegetables (eg, radishes, turnips, cauliflower, cucumbers) contain peroxidase, all of which can cause a false-positive result. Vitamin C inhibits heme peroxidase activity and leads to false-negative results. Aspirin and high-dose nonsteroidal anti-inflammatory drugs can promote bleeding throughout the intestinal tract.13

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The American Cancer Society (ACS) also includes the fecal immunohistochemical test (FIT) within its guidelines for colorectal cancer screening. The FIT is a type of FOBT, which also tests for the presence of blood in the stool.

FIT vs FOBT FIT should replace FOBT as the preferred stool screening method. Instead of an enzymatic reaction that can be altered by food or medication, FIT utilizes an antibody specific to human globin to directly detect hemolyzed blood, thus eliminating the need to modify the diet or medications.14 Additionally, only 1 stool specimen is needed, which may explain why the adherence rate was about 20% higher with FIT than with FOBT in most studies. FIT has a sensitivity of 69% to 86% for colorectal cancer and a specificity of 92% to 95%.15-19

Stool DNA Testing (sDNA)

SDNA testing is a simple, non-invasive test that looks for abnormalities known to be associated with colon cancers and colon polyps in DNA shed into the stool sample. Unlike bleeding (FOBT/FIT), which is not directly related to cancer development, often does not occur in early lesions, and may only be present intermittently, if at all, in stool samples, DNA abnormalities are fundamental to the development of all colorectal cancer,. Cells from the lining of the colon—and especially from cancers–are constantly shed in stools, where they release their DNA. Laboratory tests can detect this abnormal DNA in a stool sample. If an abnormality is detected, the patient is then referred for a colonoscopy for final diagnosis.

Unlike FOBT, sDNA testing has been designed to increase compliance with colorectal cancer screening by providing a safe, simple and non-invasive approach using a single stool specimen that requires no stool handling or manipulation by the person being screened. sDNA is designed for people who are unwilling or unable to have colonoscopy. Early data indicates that over 50 percent of people who use sDNA testing had never been screened before and that over 90 percent were very satisfied/satisfied with the collection process and were likely to use the test again in the future.13 

The sDNA test is constantly improving as more information is discovered about the genetic markers of colorectal cancer allowing for more accurate and comprehensive test panels to be prepared. Studies of a two marker sDNA test have shown the identification of over 80 percent of colorectal cancers including both early and later stages as well as the advanced polyps most likely to become malignant (high-grade dysplasia)12. The development of highly sensitive techniques to identify even single abnormal DNA molecules in stool specimens could lead to cancer detection in over 90 percent of cases.15

As with CTC imaging, the ACS and USPSTF differ in their recommendation of sDNA testing; the test is included in the ACS guidelines, but the USPSTF notes that there is still insufficient evidence to fully assess the risks and benefits. In all cases, patients should speak with their healthcare provider about which type of screening best suits their needs and personal history.

Colorectal Colon Rectal Newsletter 490

Virtual Colonoscopy

One of the most promising new advances in screening for colorectal cancer is computed tomography colonography (CTC), also referred to as virtual colonoscopy. A CTC involves the use of a computer program to develop three-dimensional images of the colon via X-rays, without the need for a scope. The hope among healthcare providers is that patients will not consider a CTC as invasive as a standard colonoscopy and will therefore be more willing to undergo screening. Similar to a standard colonoscopy, a CTC still requires bowel prep the day before the procedure as well as the infusion of air into the colon. The images of the colon, however, are obtained from X-ray machines outside the body. One drawback to a CTC is that the physician is unable to remove areas of suspicion, such as polyps, during the procedure, and patients with abnormal findings must undergo a subsequent colonoscopy.

The most recent results evaluating CTC for screening of colorectal cancer were published in the New England Journal of Medicine. This trial was conducted by researchers from the Mayo Clinic to further explore the accuracy of CTC compared with standard colonoscopy among patients who did not exhibit any signs of colorectal cancer. This trial at 15 different medical centers included 2,600 individuals 50 years or older who first underwent a CTC followed by a standard colonoscopy.

  • CTC accurately identified 90 percent of cancers measuring 10 mm (millimeters) or more in diameter.
  • CTC detected only 78 percent of smaller cancers (6 mm or greater).

CTC appears to be quite accurate in identifying larger masses (10 mm or greater) within the colon, which are more highly associated with the development of colorectal cancer than are smaller masses. Its use in identifying smaller masses is less accurate, however; and although smaller masses are not as often associated with being cancerous, their removal may prevent the development of cancer altogether. Nevertheless, an overall benefit of CTC may be realized if compliance rates are improved over standard colonoscopy. Future improvements for CTC in identifying smaller masses may include more training for the radiologists reading the CTC reports.

While CTC is currently included in the ACS guidelines for the screening of colorectal cancer, it should be noted that recent USPSTF recommendations state that there is still insufficient evidence to fully assess the risks and benefits of CTC. Patients should always be sure to speak with their healthcare provider regarding their individual risks and benefits of the different types of screening for colorectal cancer.

Double-contrast Barium Enema

Although a double-contrast barium enema is not widely used as a standard screening method for colorectal cancer, it remains an option within the NCI and ACS guidelines and may still be used for some patients. The procedure involves bowel prep followed by an enema that is filled with a chalky substance that can be viewed on an X-ray. The X-ray images of the colon can reveal abnormalities, which are then confirmed with a subsequent colonoscopy


From the bowel prep to the idea of the procedures themselves, it is perhaps not surprising that individuals come up with many creative excuses to postpone screening, particularly if they have no symptoms. Colorectal cancer is most curable prior to any symptoms, however, so delaying screening can come with the uncompromising consequence of a diagnosis of advanced cancer and, ultimately, death from the disease. Healthcare providers continue to explore novel screening methods that not only are accurate and effective but that will also seem less daunting to patients.

Barriers to Screening

As if the complicated guidelines aren’t enough of a deterrent, there are several other barriers to screening.

Dr. Goldberg says that two of the most common barriers to screening, especially with colonoscopy, are lack of insurance and lack of a primary care physician. A colonoscopy is an expensive procedure, so people without insurance are less likely to have one. What’s more, it’s typically the job of the primary care physician to recommend a colonoscopy. Many uninsured people do not have a primary care physician, which means no one is reminding them to get this procedure.

But there are other, more surmountable barriers to screening: fear and embarrassment. There is a general sense of dread surrounding the idea of having a colonoscopy. The procedure is costly, time-consuming, and downright uncomfortable. It requires a commitment to cleaning out the colon (bowel preparation) prior to the procedure, which involves restricting the diet, drinking an unpalatable liquid to clear out the bowels, and staying near the toilet. The procedure itself isn’t so bad because it happens under sedation, but that means taking it easy for the rest of the day. As a result, people just feel a natural sense of resistance to the whole thing.

What’s more, it can be a little taboo to talk about our colons. “Some people feel embarrassed about the procedure,” Dr. Goldberg says. “But it’s far more embarrassing to die of a preventable disease than it is to have a colonoscopy.”

Just Be Screened

Fear and embarrassment aside, it’s important to just be screened. Because of her experience, Michele Cofield will forever be an advocate of colonoscopy screening. “You are in charge of your body,” she says. “It’s your life, so you should do everything in your power to make it the best life possible—including getting screened.

“Yes, the prep is not fun and, yes, it takes time out of your life and can be uncomfortable,” she adds. “But if you don’t have it, the risks involved are life-threatening.”

For Michele there is no question that the screening was worth every bit of inconvenience and discomfort.

“The only way we are going to have a dramatic impact on the outcomes of colorectal cancer is early detection and prevention,” Dr. Goldberg insists. “When colorectal cancer has spread to distant sites in the body, the average survival is two years, whereas when you catch a polyp that is just turning to cancer, there is a 90 percent survival rate.”

Dr. Goldberg says that good cancer prevention strategies for women include Pap tests, mammograms, and colonoscopy—as well as a healthy lifestyle, which goes a long way toward protecting against colon cancer and heart disease.

“Everybody should get a jug of GoLYTELY® [the bowel cleansing formula] for their fiftieth birthday,” jokes Dr. Goldberg.

Colorectal cancer is no joke. Just get screened.


The paradox of colorectal cancer remains: it is easily treatable in early stages and has highly effective screening methods that can prevent the disease altogether, but it remains the second-leading cause of cancer-related deaths in this country. Researchers are hopeful that with novel screening methods resulting in higher compliance rates, the story of colorectal cancer will ultimately parallel that of cervical cancer in that deaths from the disease will be virtually nonexistent in this country as screening becomes commonplace. Every individual should speak with their healthcare provider regarding their individual risks and benefits of the different types of screening for colorectal cancer.


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About the National Comprehensive Cancer Network

The National Comprehensive Cancer Network® (NCCN®), a not-for-profit alliance of 27 leading cancer centers devoted to patient care, research, and education, is dedicated to improving the quality, effectiveness, and efficiency of cancer care so that patients can live better lives. Through the leadership and expertise of clinical professionals at NCCN Member Institutions, NCCN develops resources that present valuable information to the numerous stakeholders in the health care delivery system. As the arbiter of high-quality cancer care, NCCN promotes the importance of continuous quality improvement and recognizes the significance of creating clinical practice guidelines appropriate for use by patients, clinicians, and other health care decision-makers.

The NCCN Member Institutions are: Fred & Pamela Buffett Cancer Center, Omaha, NE; Case Comprehensive Cancer Center/University Hospitals Seidman Cancer Center and Cleveland Clinic Taussig Cancer Institute, Cleveland, OH; City of Hope Comprehensive Cancer Center, Los Angeles, CA; Dana-Farber/Brigham and Women’s Cancer Center | Massachusetts General Hospital Cancer Center, Boston, MA; Duke Cancer Institute, Durham, NC; Fox Chase Cancer Center, Philadelphia, PA; Huntsman Cancer Institute at the University of Utah, Salt Lake City, UT; Fred Hutchinson Cancer Research Center/Seattle Cancer Care Alliance, Seattle, WA; The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD; Robert H. Lurie Comprehensive Cancer Center of Northwestern University, Chicago, IL; Mayo Clinic Cancer Center, Phoenix/Scottsdale, AZ, Jacksonville, FL, and Rochester, MN; Memorial Sloan Kettering Cancer Center, New York, NY; Moffitt Cancer Center, Tampa, FL; The Ohio State University Comprehensive Cancer Center - James Cancer Hospital and Solove Research Institute, Columbus, OH; Roswell Park Comprehensive Cancer Center, Buffalo, NY; Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine, St. Louis, MO; St. Jude Children’s Research Hospital/The University of Tennessee Health Science Center, Memphis, TN; Stanford Cancer Institute, Stanford, CA; University of Alabama at Birmingham Comprehensive Cancer Center, Birmingham, AL; UC San Diego Moores Cancer Center, La Jolla, CA; UCSF Helen Diller Family Comprehensive Cancer Center, San Francisco, CA; University of Colorado Cancer Center, Aurora, CO; University of Michigan Rogel Cancer Center, Ann Arbor, MI; The University of Texas MD Anderson Cancer Center, Houston, TX; University of Wisconsin Carbone Cancer Center, Madison, WI; Vanderbilt-Ingram Cancer Center, Nashville, TN; and Yale Cancer Center/Smilow Cancer Hospital, New Haven, CT.