BACKGROUND & AIMS: The comparative effectiveness of sigmoidoscopy and fecal immunochemical testing (FIT) for colorectal cancer (CRC) screening is unknown.
METHODS: Individuals aged 50-74 years living in Southeast Norway were randomly invited between 2012 and 2019 to either once-only flexible sigmoidoscopy or FIT screening every second year. Colonoscopy was recommended after sigmoidoscopy if any polyp of =10 mm, =3 adenomas, any advanced adenomas, or CRC was found or, subsequent to, FIT >15 µg hemoglobin/g feces. Data for this report were obtained after complete recruitment in both groups and included 2 full FIT rounds and part of the third round. Outcome measures were participation, neoplasia detection, and adverse events. Age-standardized detection rates and age-adjusted odds ratios (ORs) were calculated.
RESULTS: We included 139,291 individuals: 69,195 randomized to sigmoidoscopy and 70,096 to FIT. The participation rate was 52% for sigmoidoscopy, 58% in the first FIT round, and 68% for 3 cumulative FIT rounds. Compared to sigmoidoscopy, the detection rate for CRC was similar in the first FIT round (0.25% vs 0.27%; OR, 0.92; 95% confidence interval [CI], 0.75-1.13) but higher after 3 FIT rounds (0.49% vs 0.27%; OR, 1.87; 95% CI, 1.54-2.27). Advanced adenoma detection rate was lower in the first FIT round compared to sigmoidoscopy at 1.4% vs 2.4% (OR, 0.57; 95% CI, 0.53-0.62) but higher after 3 cumulative FIT rounds at 2.7% vs 2.4% (OR, 1.14; 95% CI, 1.05-1.23). There were 33 (0.05%) serious adverse events in the sigmoidoscopy group compared to 47 (0.07%) in the FIT group (P = .13).
CONCLUSIONS: Participation was higher and more CRC and advanced adenomas were detected with repeated FIT compared to sigmoidoscopy. The risk of perforation and bleeding was comparable. Clinicaltrials.gov, Number: NCT01538550.
One advantage of this trial will be some insight into FIT, as trials comparing FIT to colonoscopy assess 2 screening tests for which we have no data from RCTs establishing efficacy in reducing colorectal mortality. (That information is only available for flexible sigmoidoscopy [FS] and guaiac-based fecal occult blood testing.) As detailed in the Discussion section of the paper, it remains to be seen if identifying more cancers (albeit at a slightly later stage) and advanced adenomas, but fewer non-advanced adenomas, will make a difference in cancer morbidity or mortality (the important outcomes). Inadequate FSs (31% of the time) and relatively inexperienced endoscopists may also prove to be trial limitations. Another confounding factor was the informed consent process, which was active for those undergoing FS but passive for those undergoing FIT. It is not clear if this difference will have any short- or long-term effect on the study participants.
This is an impressive study, randomizing nearly 140,000 people aged 50-74. However, it is of less relevance in many high income countries as flex sig is not really an acceptable alternative (as compared to colonoscopy). So, this study is precisely answering a question that is no longer all that relevant.
Screening sigmoidoscopy rarely done, so not really relevant.
This study confirms current guidelines.
These are data for public health team looking into the full evidence base in designing screening programmes rather than primary care clinicians making clinical decisions.
This is a very large population study to compare two approaches for screening of colorectal cancer. It is a very needed issue to provide evidence on a frequent massive testing. The conclusions highlight the advantage of the less aggressive and less-resource consuming approach.