Screening colonoscopy is more effective than sigmoidoscopy for the detection of colorectal cancer by picking up proximal advanced serrated lesions, according to the results of a study published in the February issue of Clinical Gastroenterology and Hepatology.

“Colonoscopy allows the detection and removal of precursor polyps during the same session and is the final common pathway for other screening modalities,” wrote lead author Dr. Charles J. Kahi of Indiana University, Indianapolis, adding that “sigmoidoscopy is an attractive option because it is more straightforward to perform, is less burdensome, and is associated with lower risk for harm than colonoscopy.”

In a retrospective, cross-sectional study, Dr. Kahi and his associates culled data on 1,910 patients who underwent an average-risk screening colonoscopy from August 2005 through April 2012 at Indiana University Hospital and an associated ambulatory surgery center. All patients included were at least 50 years of age, with an average age of 59.3 years ± 8.0 years, and women represented 53.8% of the population (Clin. Gastroenterol. Hepatol. 2015 February [ doi:10.1016/j.cgh.2014.07.044 ]).

All subjects had colonoscopies performed by an endoscopist with “documented high adenoma and serrated polyp detection rates;” when found, tissue samples of all serrated polyps – hyperplastic (HP), sessile serrated adenoma/polyp (SSA/P), or traditional serrated adenoma – were also proximal to the sigmoid colon and serrated polyps larger than 5 mm in the rectum or sigmoid colon were also taken and “reviewed by a gastrointestinal pathologist and reclassified on the basis of World Health Organization [WHO] criteria.”

The WHO classifications for serrated polyps fall into HP, SSA/P with cytologic dysplasia, sessile serrated polyp with cytologic dysplasia (SSA/P-CD) of at least 10 mm, and traditional serrated adenoma (TSA). Advanced conventional adenomatous neoplasia (ACN) was defined as tubular adenoma of at least 10 mm, villous histology, high-grade dysplasia, or cancer. The prevalence of both proximal advanced serrated lesion (ASL) and ACN was calculated based on distal colorectal findings; investigators also performed multivariable logistic regression analysis to determine age-adjusted and sex-adjusted odds of advanced proximal adenomatous and serrated lesions, while “secondary analyses were performed to examine the effect of variable ASL definitions.”

Results indicated that of the 1,910 subjects in the study population, 52 (2.7%) were found to have proximal ASL, while 99 (5.2%) had proximal ACN. Of the 52 individuals with proximal ASL, 27 (52%) had no distal polyps, while 40 (40%) of the 99 subjects with proximal ACN also had no distal polyps. A total of 1,675 patients (87.7%) had no family history of colorectal cancer (CRC); of the remaining 235 patients, 212 (11.1%) had a first-degree relative and 23 (1.2%) had a distant relative with the condition.

Age and type of distal neoplasia, with the exception of nonadvanced serrated lesions, were associated with proximal ACN; however, only patient age was significantly associated with proximal ASL. Investigators found no significant associations between distal polyps and proximal ASL, and in secondary analyses, presence of a distal SSA/P was the lone factor associated with a proximal SSA/P. The authors also found no significant associations with either age or sex.

“These findings are relevant for CRC screening strategies that use sigmoidoscopy as a ‘gateway’ test and triage patients to colonoscopy on the basis of findings at sigmoidoscopy,” the authors note, adding that “for example, a patient with no polyps at sigmoidoscopy who is not referred for a follow-up colonoscopy exclusively on the basis of the estimated risk of advanced ACN could be harboring significant serrated lesions in the proximal colon that would go undetected.”

Funding was provided by a gift from Scott and Kay Schurz of Bloomington, Ind. No financial conflicts of interests were reported.