Colonoscopy Frequently Asked Questions: When to start? How often? When to stop? Alternatives?

September 1, 2019

This blog entry reviews some commonly asked questions pertaining to colonoscopy and colon cancer screening.

Dear Patient,

Those of you who have had physical exams with us or other physicians probably have been advised to have screening (initial) and surveillance (follow-up) colonoscopy exams. But there remains considerable reluctance, resistance and misunderstanding about the value and timing of colonoscopy. As usual, the internet is full of misinformation. Here are some of the most frequently asked questions we get from patients and referring physicians:

1. Is colonoscopy the best way to discover colon cancer? One reason why colon cancer is one of the leading cancer killers is that it may be advancing without giving any symptoms at all. We believe that colon cancer arises from polyps (initially small pea-sized growths) that, if left undiscovered or not removed, can degenerate into colon cancers. Colonoscopy is the best way to discover and, in most cases, simultaneously remove potentially pre-malignant polyps. That is, colonoscopy can be both diagnostic and therapeutic. Colonoscopy also is the best test to discover any cancers that have already developed. We must admit that colonoscopy is not perfect; some polyps or even occasional cancers can be missed even by the most experienced and meticulous colonoscopists. But colonoscopy remains the gold standard for colon polyp and cancer detection.
2. At what age should colonoscopies begin? Guidelines have been set at age 50. But this has been challenged by a recent observed increase in colon cancers in younger people. In fact last year the American Cancer Society lowered the recommended age for first colonoscopy to 45. As with other recommendations this advice has to be individualized. The 45 or 50 year guideline is for patients who have no close relatives with colon cancer or polyps. For those with polyps and cancer in the family the first colonoscopy should be by the age of 40 or, if there has been colon cancer in your family your first colonoscopy should be 10 years earlier than the age that that relative was found to have colon cancer.
3. How often should colonoscopies be done? That depends on what was found at previous colonoscopy. If the exam discovered no polyps or cancer you can wait up to 10 years before having another colonoscopy—unless you develop worrisome symptoms like change in bowel habits, blood in you bowel movements or an iron deficiency anemia. But if polyps were found and removed at your previous colonoscopy you should have another exam within 3 to 5 years, depending on what type of and how many polyps had been detected and removed.
4. At what age can I stop having colonoscopies? Again, this depends on what had been found on previous colonoscopy exams. If previous colonoscopies were normal you probably can stop having colonoscopies in your 80’s. But if you have had colon polyps or cancer or a strong family history of colon cancer you should continue to have colonoscopies as outlined in question 3 above, as long as your general health permits. These details are missing from many reports in the general media.
5. What are alternatives to colonoscopy? Alternatives include:
   1. testing stool for hidden blood or sending it to a specialized laboratory to analyze its DNA for big polyps and cancer.
   2. CT scan (so-called virtual colonoscopy)
   3. Although these stool and radiographic tests are better than no testing at all they are less accurate than colonoscopy, cannot sample or removed any abnormal growths, and, if positive, will require colonoscopy to confirm and hopefully remove pre-malignant polyps.

We hope this updates and clarifies the issue of colonoscopy. If you have any questions or concerns please contact us.

—Peter H. Rubin, MD