There were higher detection rates for advanced adenomas and colorectal cancer (CRC) with three rounds of cumulative fecal immunochemical testing (FIT) compared to one-time sigmoidoscopy, a study found.
In 2012, researchers identified all individuals ages 50 to 74 years living in two areas in Norway through the population registry and randomly assigned them in a 1:1 ratio to be invited for once-only flexible sigmoidoscopy or to FIT every second year for a maximum of four rounds. The trial's primary end point was CRC mortality after 10 years, and secondary end points included attendance rate, neoplasia detection rate, CRC stage at diagnosis, and adverse events after endoscopy (e.g., bleeding, perforation). Researchers defined significant bleeding as bleeding events leading to hospitalization, blood transfusion, repeat endoscopy, radiological intervention, or surgery. Perforation was determined by CT findings. Colonoscopy was recommended after sigmoidoscopy if any polyp was 10 mm or larger, or if there were three or more adenomas or any advanced adenomas, if CRC was found, or if FIT results were more than 15 µg hemoglobin/g feces. While the Norwegian government funded the trial, Ferring Pharmaceuticals provided the bowel preparation used for colonoscopy free of charge. Results were published online on Nov. 20 by Gastroenterology.
The study included 139,291 individuals, 69,195 randomized to sigmoidoscopy and 70,096 to FIT. Participation rates were 52% for sigmoidoscopy, 58% for the first FIT round, and 68% for at least one FIT round. Of note, participation was already higher in the first round of FIT compared to sigmoidoscopy and increased in the second and third screening rounds. Compared to sigmoidoscopy, the detection rate for CRC was similar in the first FIT round (0.25% vs. 0.27%; odds ratio [OR], 0.92 [95% CI, 0.75 to 1.13]) but higher after three FIT rounds (0.49% vs. 0.27%; OR, 1.87 [95% CI, 1.54 to 2.27]). The advanced adenoma detection rate was lower in the first FIT round compared to sigmoidoscopy (1.4% vs. 2.4%; OR, 0.57 [95% CI, 0.53 to 0.62]) but higher after three cumulative FIT rounds (2.7% vs. 2.4%; OR, 1.14 [95% CI, 1.05 to 1.23]). The adverse event rates did not differ between the two screening methods (0.05% [n=33] in the sigmoidoscopy group vs. 0.07% [n=47] in the FIT group; P=0.13).
The higher number of advanced adenomas in the FIT group compared to the sigmoidoscopy group may indicate a potential effect not only on CRC mortality but also CRC incidence reduction; however, more non-advanced adenomas were removed by sigmoidoscopy screening than by FIT, the study authors said. “A higher detection rate of advanced adenomas with cumulative FIT rounds may be caused by transformation of non-advanced adenomas over time,” they wrote. “This may imply that once-only sigmoidoscopy [will] detect most adenomas at a non-advanced stage, while repeated FIT screening over time will detect more adenomas at an advanced stage. Thus, FIT screening may not be more effective than sigmoidoscopy screening to reduce CRC incidence.”