Miriam E. Tucker

October 09, 2013

WASHINGTON, DC — The chance that a screening sigmoidoscopy will miss a potentially cancerous polyp increases with age, and is up to 50% for people 70 years and older, an analysis of more than 120,000 colonoscopies has found.

Data from the study — one of the largest of its kind to date — were presented here at the American College of Surgeons 2013 Annual Clinical Congress by Victor Tsirline, MD, from Northwestern University in Chicago.

"From this study, it's evident that proximal colon polyps are more frequent with advancing age, and it's pretty apparent that sigmoidoscopy should not be used for cancer screening, especially in older individuals," said Dr. Tsirline. The work was conducted during his fellowship at the Carolinas Medical Center in Chapel Hill, North Carolina.

"There are a large number of patients who don't have polyps in the sigmoid, especially as they age, but who have a large number in the right colon, transverse colon, and cecum that otherwise would be missed," added lead investigator Todd Heniford, MD, from the Carolinas Hernia Center in Charlotte. "What these data demonstrate is that as you age, sigmoidoscopy would be less preferable."

Session moderator Alessandro Fichera, MD, from the University of Washington in Seattle, said he agrees. "I've always told my patients to get a colonoscopy, even before this study," he told Medscape Medical News.

Polyp Location Varies

Dr. Tsirline noted that the US Preventive Services Task Force (USPSTF) currently recommends 2 screening options for adults 50 to 75 years of age: a colonoscopy every 10 years, or a flexible sigmoidoscopy plus fecal occult blood test every 5 years. Screening is not routinely recommended for people 76 to 85 years, and there are no screening recommendations for adults older than 85 years.

The recommendations presume that if no polyps are found in the sigmoid colon, the remainder of the colon is likely to be clear. However, data from this analysis suggest otherwise.

Dr. Tsirline and colleagues used a computer algorithm to identify 120,365 colonoscopies conducted from June 2003 to October 2011 on patients 20 to 90 years of age.

At least 1 polyp was identified in 54,190 of those procedures (64% had just 1 polyp, 25% had 2, and 11% had 3 or more). Polyps were adenomatous in 48% of cases, hyperplasic in 37%, and unknown in 15%.

Table. Location of the Polyps

Location Percent
Cecum 10
Ascending colon 15
Transverse colon 15
Descending colon 12
Sigmoid 25
Rectum 17


Patients younger than 60 had slightly more polyps in the rectum and sigmoid, whereas those older than 60 had slightly more in the ascending colon and cecum. A decade-by-decade analysis "pretty clearly demonstrated that patients with increasing age tend to have more polyps proximally," Dr. Tsirline said.

Statistical modeling showed that the probability of finding a polyp in the cecum rose by 22% with each decade of life. For the ascending colon, the probability rose by 30% per decade, for transverse colon it rose by 19%, and for descending colon it rose by 7%.

In contrast, the probability of finding a polyp in either the sigmoid or the rectum decreased by 12% per decade of life, Dr. Tsirline reported.

All of those probability values were significant.

A subsequent analysis of just the adenomatous polyps — considered to be precancerous — yielded similarly significant increases in probability per decade for the cecum (22%), ascending colon (24%), and transverse colon (10%), and decreases for the sigmoid (13%) and rectum (15%).

Hyperplastic (benign) tumors, in contrast, showed no such pattern. There were also no differences by sex, Dr. Tsirline noted.

Implications for Screening

The data suggest that if sigmoidoscopy had been used instead of colonoscopy for screening, 22,885 total polyps and 16,806 adenomatous polyps would have been missed. In people 30 to 49 years of age, about 33% to 36% of polyps would have been missed, and in those 50 to 79 years of age, 45% to 51% would have been. In octogenarians, about 56% of polyps would have been missed with sigmoidoscopy.

An audience member asked whether these data suggest that adults older than 75 should be routinely screened, despite the USPSTF recommendation against it. Dr. Tsirline explained that the rationale for not screening older adults has more to do with whether any action would result from the findings.

"For the purposes of this study, we included the data that were available, but we focused on people in their 60s and 70s. Beyond that, it's arguable whether they should be screened," even though the trend continues, he added.

Dr. Fichera said the reason for the difference in polyp location by age is not clear, and noted that it would be useful to study people over time to determine patterns. "Do polyps start proximally and go distally. Do people have polyps on one side and not the other? This study didn't answer those questions. The question it answered, though, is that you need to do a full colonoscopy."

"In my opinion, anybody with symptoms such as bleeding should be referred for a full colonoscopy, irrespective of age," Dr. Fichera advised. "In the study, there were several patients younger than 50 with polyps."

Dr. Tsirline, Dr. Heniford, and Dr. Fichera have disclosed no relevant financial relationships.

American College of Surgeons (ACS) 2013 Annual Clinical Congress. Presented October 8, 2013.


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