Frequently Asked Questions

Dr. David Johnson, professor of medicine and chief of gastroenterology of Eastern Virginia School of Medicine, and Dr. James C. Hobley, assistant professor at the Penn State University of Medicine, share some of the most frequently asked questions. Read below to find out more.

• What causes a polyp to form?

  Dr. Hobley: One theory is that polyps form because of damage to chromosomes which in turn allow the tissue associated with them to grow uncontrolled, hence forming polyps or growths.

• How can you prevent polyps from forming?

  Dr. Hobley: There have been studies, some of which have been surrounded in controversy, which have looked into some common medications as possible means to preventing polyp formation. There have also been some studies which suggest diets high in fiber lead to less polyp formation. None of these studies have been scientifically proven.

• Exactly what is a "precancerous" polyp?

  Dr. Hobley: A precancerous polyp is any polyp that has not yet progressed on to have cancer cells within it. These polyps have the potential of becoming cancerous if left in place.

• If the polyp is removed does that mean I am cured?

  Dr. Hobley: Removal of the polyp during a colonoscopy effectively "cures" a person from that individual polyp's chances of becoming malignant (or cancerous).

• Can polyps "fall off" or take care of themselves without having them removed?

  Dr. Johnson: The simple answer here is virtually never. It would be foolish and dangerous to ever take the chance of not having precancerous colon polyps removed appropriately by experts.

  Dr. Hobley: Polyps don't typically "fall off" or "take care of themselves." They require a trained professional to remove them.

• What foods or what diet should I follow to prevent colorectal cancer from occurring?

  Dr. Hobley: A high-fiber, low-fat diet, enriched with roughage and devoid of processed food is an ideal diet that may help in colorectal cancer prevention.

• Can flaxseed or green tea prevent colorectal cancer?

  Dr. Hobley: Green tea has antioxidant properties that have been shown to reduce the formation of cancers. There are no controlled studies involving tea; however, there have been observational studies that show a benefit. Flaxseed has no particular relation to the prevention of colon cancer.

• Does fiber play a protective role in colorectal cancer?

  Dr. Hobley: Fiber does show a protective role in the prevention of colon cancer. This is also why the western diet, which is low in fiber is considered a contributory factor in colon cancer's prevalence in the U.S.

• Does food intolerance or lactose intolerance increase your risk for colon or rectal cancer?

  Dr. Hobley: Generally, food or lactose intolerance has no true relationship to developing colon cancer.

• What are early symptoms of this type of cancer?

  Dr. Hobley: Symptoms are varied but a general list may include: fatigue, weakness, shortness of breath, change in bowel habits, narrow stools, diarrhea or constipation, red or dark blood in stool, weight loss, abdominal pain, cramps, or bloating.

• Is it possible to have colon or rectal cancer without having polyps?

  Dr. Hobley: People with certain types of diseases such as colitis (Crohn's or ulcerative colitis) may develop colon cancer without developing polyps first.

• Is it possible to have blood in your stool, but not have colon cancer?

  Dr. Johnson: Yes- but blood in the stool should always prompt a thorough evaluation with a prime focus of concern being to exclude colorectal cancer. Clearly bleeding can come from many things which are not cancerous — but patients should NEVER fail to bring this report of bleeding immediately to the attention of their physician!

  Dr. Hobley: Blood in the stool may mean many things without definitely being cancer; however, blood should not be disregarded, as it is a common presenting symptom of colon cancer.

• Are intestinal obstructions an early symptom of colon cancer?

  Dr. Hobley: Intestinal obstructions are generally considered to be a late manifestation of colon cancer.

• What is the best colon cancer screening test?

  Dr. Hobley: The gold standard for screening for colon cancer at the present time is colonoscopy, which is both diagnostic (i.e. finding the polyp) and therapeutic (removing the polyp).

• Does your general practitioner do colorectal screening tests or should gastroenterologists or other experts do them?

  Dr. Johnson: As some CRC screening tests do not involve endoscopy, primary care providers may chose to offer or perform these, in particular stool based testing.  Colonoscopy however should be performed by physicians who are highly skilled and trained in both the technical skills of colonoscopy to recognize polyps and in the management and treatment of polyps when they are found. There are presently three studies in the published literature which show that the cancer and polyp detection rate for gastroenterologists is at least 3-4 times higher than primary care providers performing colonoscopy.  Limitations with regard to detection of colon polyps and cancer and the fact that colonoscopy is dependent upon the skill set of the physician is an extremely important limitation for patients to recognize.  Although clearly the best test for polyp detection and removal, colonoscopy is not an infallible “gold standard”.  Controlled studies have shown the colonoscopy miss rate for large adenomas (> 10 mm) to be 6-12%. The reported colonoscopy miss rate for cancer is about 5%. Hence patients should question the experience and quality performance of their colonoscopist. Precancerous (adenoma) detection rates on screening colonoscopy should be > 15% for women and > 25% for men.

  Dr. Hobley: A colonoscopy is usually performed by a gastroenterologist (GI physician) or a surgeon who has trained and been certified in performing this specialized test. There is a society dedicated to endoscopic training and development called the ASGE which has credentialing information. To find an ASGE doctor near you log on to: http://www.crcawareness.com/treatable.asp.

• Is there a correlation between the length of your colon and colon cancer?

  Dr. Hobley: There is no correlation between the length of your colon and your risk of colon cancer.

• Is there a connection between other cancers and colorectal cancer?

  Dr. Hobley: There are other cancers that may suggest an underlying syndrome, which raises the risk of developing colon cancer. These other cancers include: extra colonic cancers such as endometrial, ovarian, small-bowel, transitional cell of the ureter or bladder, and gastric cancer.

• Is Irritable Bowel Syndrome a risk factor for developing colorectal cancer?

  Dr. Hobley: Irritable bowel syndrome is not a known risk for developing colon cancer.

• Can young people get colon cancer? If there is no family history and if the person is under 30, should they be concerned about getting colon cancer?

  Dr. Hobley: Typically, people without a family history of colon cancer in young people or those who do not have a family history of the cancers listed above, do not carry any significant risk of developing cancer at that young age.

• Are there any colon cancer differences associated with gender or race?

  Dr. Johnson: There is a slightly delayed development of precancerous polyps and cancers in women, but the recommendations for age to begin screening are no different. As women's lifetime expectancy is in general, longer than a man's, the overall lifetime risk of cancer is very similar for men and women. For African Americans, there is an earlier onset of cancers and these tend to be more aggressive, hence the recommendations by national society guidelines to begin screening at age 45 instead of the general recommendation — at age 50.

  Dr. Hobley: Recent studies have found significant disparities in colon cancer in relation to both gender (women are "less likely" than men to be screened) and ethnicity (African Americans are more likely to die from colon cancer). Arch Intern Med 2007; 167 258-264.

• Amongst each of the various modalities of screening (CT Colonography, Colonoscopy, Sigmoidoscopy, etc.), what are the risks associated with each?

  Dr. Johnson: Clearly there are risks with any test even those that are viewed as "safe" and individuals should consider the benefits and risks of each screening test or procedure prior to undergoing the examination. This involves not only an assessment of the direct risks of performing the specific test or procedure, but also an understanding of the risks/benefits associated with what may be found or missed should one test be chosen or rejected as an option. Furthermore, one's assessment should include downstream risks (and costs) of additional tests which may be warranted as a result of the findings for the initial test/procedure.

  The chief limitation of flexible Sigmoidoscopy is that it does not examine the entire colon. Under optimal conditions, only the rectum, sigmoid and descending colon can be examined. The complications of flexible sigmoidoscopy include colonic perforation, even if no biopsy or polypectomy is performed, but this occurs in fewer than one in 20,000 examinations.

  Colonoscopy does have a significant risk, most often associated with the removal of polyps. The most significant complications of polyp removal are bleeding and perforation (a hole through the colon). The risk of bleeding related to post-polyp removal increases relative to the size of the polyp (the larger the polyp, the greater bleeding risk)and the location of these polyps in the right colon. Another significant risk associated with colonoscopy is perforation. Perforation increases with increasing age and the presence of diverticular disease, but this was recently estimated to approximately 1 in 1,000 screened patients overall.

  Diverticular Disease:
  The presence of small sacs in the walls of the lower end of the colon. Diverticula are created by the bulging or protrusion of the inner lining of intestinal walls through the muscular layers of the wall. It is especially common in mature Americans where the diet is typically low in fiber and constipation is a problem.

  There is a commonly held notion that CT Colonography (CTC) "virtual colonoscopy" has a lower chance of complications such as "colon perforation." In fact, there are two very large studies involving CTC that cite a perforation rate which is near the rate of colonoscopy:   1) Sosna J et al. Colonic perforation at CT colonography: Assessment of risk in a multicenter large cohort. Radiology 2006 May; 239:457-63. 2) Burling D et al. Potentially serious adverse events at CT colonography in symptomatic patients: National survey of the United Kingdom. Radiology 2006 May; 239:464-71. In the first study, researchers reviewed data from 11,870 CTC studies performed at 11 centers in Israel during a 2-year period. These studies represented more than 95% of all CTC studies performed in Israel during this interval. Seven perforations occurred, yielding a rate of 1 in 1700 (0.06%). Five perforations occurred in the sigmoid colon and two in the rectum. Four patients required surgical treatment. In the second study, researchers interviewed the lead gastrointestinal radiologists at 50 centers in the UK to determine the number of CTCs ever performed and the number of perforations. Of 17,067 patients who underwent CTC, 9 had perforations (1 in 1900 or 0.05%). These rates are close to the average perforation rate seen with colonoscopy, which is about 1 in 2,000 based on a number of studies.

  Considerable concern has been raised recently about radiation exposure over a lifetime of directed testing and screening. Because CTC involves radiation, this has been an issue of hot discussion, since the side effects and potential risk related to the repeated use of this screening modality may not be evident for many years after exposure. The risks are higher for abdominal scans because the digestive organs are more sensitive for radiation-induced cancer. Extrapolating from the data published by experts, the risk of cancer related death associated with one abdominal CT is 0.06% for a patient exposure at 25 years of age and 0.02% for a patient exposed at age 50. This risk is striking and apparent when looking at the lifetime radiation risk of two of the most common radiogenic cancers — namely lung and colon cancer. For individuals exposed to as little as 10 mSv at 25 years of age, the incremental risk of death from lung or colon cancer is .025% and 0.0125% respectively. For individuals exposed to this same amount of radiation at 50 years these associated risks decrease to 0.017% and 0.010% from lung or colon respectively.

Dr. David A. Johnson is a professor of medicine and chief of gastroenterology at Eastern Virginia School of Medicine. He is the past president of the American College of Gastroenterology. As a renowned author of more than 350 articles, his work in colorectal cancer is highly acclaimed and regarded. His depth of expertise with regard to colon cancer is one reason why he serves as a consultant for the Centers for Medicare and Medicaid Services and the American Quality Alliance.

Dr. James C. Hobley is an assistant professor at the Penn State University College of Medicine and a fellow in Gastroenterology and Hepatology at the Milton S. Hershey Medical Center. Hobley is a member of the American Medical Association and the American College of Physicians. He has published multiple works on the risks of colon cancer.