Detection rates for advanced adenomas and colorectal cancer (CRC) were superior with three cumulative rounds of biennial fecal immunochemical testing (FIT) versus once-only sigmoidoscopy, baseline results from a randomized, comparative effectiveness trial in Norway showed.
After three rounds of FIT, the CRC detection rate was almost double that for flexible sigmoidoscopy, reported Kristin R. Randel, MD, of the Cancer Registry of Norway in Oslo, and colleagues.
Furthermore, as shown in their study online in Gastroenterology, participation was higher in the FIT programs and safety was similar.
The results of the trial, undertaken in preparation for the launch of Norway's first national screening program in 2021 of individuals age 55 and older, suggest that FIT screening might confer greater protection against proximal cancer development and death in the long term compared with sigmoidoscopy screening, the researchers said. "This may be explained by FIT detecting bleeding in the entire colon, while sigmoidoscopy is only examining the distal colon and rectum."
Study Details
During 2012 to 2018, residents in two areas of South-East Norway in the 50-to-74 age group were randomly invited to undergo either once-only flexible sigmoidoscopy or FIT screening every 2nd year for a maximum of 4 years. The last sigmoidoscopy was performed in 2019.
Colonoscopy was recommended if sigmoidoscopy found any polyp that was at least 10 mm, three or more adenomas, any advanced adenomas, or CRC; or if FIT found blood in the stool at a threshold of more than 15 µg hemoglobin/g feces.
The study assigned 69,195 participants to sigmoidoscopy and 70,096 to FIT. The median age at initial invitation was 63.3 years (IQR 58.0- 69.3) in the sigmoidoscopy group and 62.2 years (IQR 56.6- 68.1) in the FIT group. Ultimately, a total of 44,016 people (63%) were included in the analyses of three cumulative FIT rounds.
Participation rates varied, with participation greater for FIT than sigmoidoscopy for both genders and all age groups (50-59, 60-69, and 70 and older), and also greater for males than females in the FIT arm. Overall, participation rates were as follows:
- 52.1% for sigmoidoscopy
- 58.4% in the first FIT round
- 68.4% after three cumulative FIT rounds
Comparative detection rates also varied, with FIT gaining ground over time:
- For CRC diagnosis, first FIT round: 0.25% (173 patients) vs 0.27% (202 patients) with sigmoidoscopy (odds ratio OR 0.92, 95% CI 0.75-1.13); after three FIT rounds: 0.49% vs 0.27% (OR 1.87, 95% CI 1.54-2.27)
- For advanced adenomas, first FIT round: 1.4% vs 2.4% (OR 0.57, 95% CI 0.53-0.62); after three cumulative FIT rounds: 2.7% vs 2.4% (OR 1.14, 95% CI 1.05-1.23)
- For non-advanced adenomas, age-adjusted detection rate in the three FIT rounds: 5.8% vs sigmoidoscopy 9.1% (OR 0.62, 95% CI 0.59-0.65)
Safety was similar, with 33 serious adverse events reported in the sigmoidoscopy group (0.05%) compared with 47 (0.07%) in the FIT group (P=0.13).
Not So Applicable in U.S., However
Regarding applicability in the U.S., however, Lukasz Kwapisz, MD, of Baylor College of Medicine in Houston, who was not involved with the study, told MedPage Today: "Unfortunately, this study is unlikely to be helpful in the U.S., where the first-tier tests for colon cancer screening include colonoscopy rather than flexible sigmoidoscopy every 10 years and FIT testing annually. This fundamentally makes comparability to our patient population difficult to ascertain."
Kwapisz noted that Norway's proposed screening program will use biennial FIT starting at age 55. "This is in stark contrast to the United States, where there is an updated push from the U.S. Preventive Services Task Force to begin screening at the age of 45, which many of us have now adopted into our practice."
Nevertheless, he said the study is important: "The most important conclusion is to emphasize how significant and valuable screening for colon cancer can be," he said. "National screening programs have the ability to save lives and need to be implemented around the world."
Regarding the study's generalizability, Randel and co-authors acknowledged that the results may not be applicable to populations with different prevalences of colonoscopy history, and with the study's relatively low threshold of 15 µg/g for FIT positivity, the findings may not be generalizable to programs with other cutoff values.
Similarly, the findings regarding participation and effects might not be generalizable to populations with different socioeconomic backgrounds and education levels, the team said.
Other study limitations included an issue with randomization at one point in 2012 and a slower invitation rate for sigmoidoscopy, which led to a mean age difference of a year at the time of first invitation between the two study groups. In addition, data from the third FIT round were incomplete (63%), and there was no information about non-study colonoscopies that might have been performed before or during the course of the trial. Also, the implementation of a nationwide screening program may ultimately alter long-term outcomes in the two trial arms.
Randel and co-authors also noted that individuals in the same household were randomized to different arms of the trial, which might have influenced participants' behavior in ways relating to the screening method or outcome. Furthermore, the researchers said, with the increasing awareness of serrated lesions over the past 2 decades, there was a possibility that serrated lesions may have been inconsistently classified during the trial, and the high number of inadequate sigmoidoscopies may have affected the detection rate in the sigmoidoscopy arm.
Disclosures
The study was funded by the Norwegian Parliament; the bowel preparation used for colonoscopy was provided free of charge by Ferring Pharmaceuticals.
Randel was supported by the South-Eastern Norway Regional Health Authority; a co-author reported financial relationships with Tillotts Pharma, Janssen-Cilag, Pfizer, Takeda, Intercept Pharma, and AbbVie, outside of the study.
Kwapisz reported no competing interests.
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