Screening for Colon Cancer (video series)

The Journal of the National Cancer Institute published an article saying that colonoscopy for primary screening might be going too far. I agree! The benefits, harms, and costs have not been determined. Checking the stool for ocult blood and flexible sigmoidoscopy have been shown to be of value but there's no data showing that colonoscopy gives additional protection. Virtual colonoscopy is even more questionable as if there are abnormal findings one still has to do a colonoscopy and there's the issue of radiation damage and later cancer risk.

Yet the American College of Gastroenterology and the National Comprehensive Cancer Network continue to recommend colonoscopy as a primary screening tool. Because of the obvious conflict of interest this is not very surprising.

The benefits of colonoscopy is that 1 in 200 people will have a major benefit from the procedure. However the same number will have either a perforation of the colon or major bleed that requires transfusions. In addition colonoscopy misses a lot of right sided cancers even though it is recommended that all polyps are removed, even those that are of no danger.

Colonoscopy Screening Questioned

Is there a need for virtual colonoscopies? In fact, is there a need for any colonoscopies in asymptomatic people? There is a lot of controversy on this topic. The advantage of virtual colonoscopy is that it is easier for the patient, but it also delivers a hefty dose of radiation and often required a regular colonoscopy if there are abnormal findings.

When do you need a colonoscopy? An article in Annals of Internal Medicine in May of 2012 stated that there's insufficient evidence to recommend earlier or more frequent colonoscopies for people who have a first degree relative with a precancerous polyp unless the polyp is advanced. About 30-50% of people have polyps that are precancerous, but only 5-10% warrant more frequent colonoscopies. The US Preventive Services Task Force recommends the same, but the American Cancer Society and the American College of Gastroenterology recommend an accelerated screening program. The financial conflicts of interest of the ACS and ACG likely are responsible for this position in my opinion. However, although it is doubtful, it is also possible that another reason for this difference of opinion is related to their concern to provide optimal screening. Colonoscopy is associated with potentially serious bleeding or possible perforation of the gut in 1 of every 200 procedures.

The May of 2012 issue of the New England Journal of Medicine reports that sigmoidoscopy rather than colonoscopy could be used to screen for colon cancer. A clinical trial of 150,000 people was done where half had sigmoidoscopy and the other have nothing. They were followed over 12 years and over that interval there were 89 fewer cancer deaths and 275 more colon cancers found in the group getting the sigmoidoscopy. These numbers can be translated to show that 749 of 750 sigmoidoscopies would be unnecessarily done to save one death and that 499 of 500 sigmoidoscopies would needlessly be done to find one cancer. This sound a lot different than when one looks at percentages rather than real numbers.

When using percentages, it can be stated that people would be 21% less likely to develop cancer and 26% less likely to die if a sigmoidoscopy were done to screen for colon cancer. The US Preventive Services Task Force agrees that sigmoidoscopy is a reasonable alternative for colonoscopy because it works nearly as well as a colonoscopy, is far less expensive, safer, and much less invasive.