Single Colonoscopy or Two Series of Faecal Immunochemical Tests 2 Years Apart for Colorectal Cancer Screening (SCREESCO): Preliminary Report of a Randomized Controlled Trial


Screening for colorectal cancer is done by lower gastrointestinal endoscopy or stool-based tests. There is little evidence from randomized trials showing that primary colonoscopy reduces mortality in colorectal cancer. Our aim was to study the effect of screening with a single colonoscopy or two sets of fecal immunochemical tests on mortality and incidence of colorectal cancer.


We performed a randomized controlled trial in Sweden (SCREESCO). Residents of 18 of the 21 regions aged 60 in the year of randomization were identified from a population register maintained by the Swedish Tax Agency. A statistician no longer involved in the trial used a randomized block method to assign individuals to a single colonoscopy, two sets of fecal immunochemical tests (OC-Sensor; 2 years apart) or a group control (no intervention; standard diagnostic pathways), in a ratio of 1:6 for colonoscopy to control and 1:2 for fecal immunochemical testing to control. Masking was not possible due to the nature of the trial. The primary endpoints of the trial are colorectal cancer mortality and colorectal cancer incidence. Here, we report preliminary participation rates, baseline outcomes, and adverse events from March 2014 through December 2020, in both intervention groups after completion of recruitment and screening, through completion of the second cycle of fecal immunochemical tests. Analyzes were performed in the intent-to-screen population, defined as all individuals who were randomly assigned to the respective study group. This study is registered with, NCT02078804.


Between March 1, 2014 and December 31, 2020, 278,280 people were included in the study; 31,140 were assigned to the colonoscopy group, 60,300 to the fecal immunochemical test group and 186,840 to the control group. 10,679 (35 1%) of the 30,400 people who received an invitation for a colonoscopy participated. 33,383 (55.5%) of 60,137 individuals who received a postal fecal immunochemical test participated. In the intent-to-screen analysis, colorectal cancer was detected in 49 (0.16%) of 31,140 people in the colonoscopy group versus 121 (0.20%) of 60,300 people in the fecal immunochemical test group (relative risk [RR] 0 78, 95% CI 0 56–1 09). Advanced adenomas were detected in 637 (2 05%) people in the colonoscopy group and 968 (1 61%) in the faecal immunochemical test group (RR 1 27, 95% CI 1 15–1 41) . Colonoscopy detected more advanced adenomas on the right side than fecal immunochemical tests. There were two perforations and 15 major bleeds in 16,555 colonoscopies. No procedure-related deaths occurred.


The diagnostic yield and low number of adverse events indicate that the design of this trial, both for single colonoscopy and fecal immunochemical test screening, could be transferred to a population-based screening service if a benefit on Disease-specific mortality is subsequently shown.


Swedish Regions, County Council, Regional Cancer Center Mellansverige, Swedish Cancer Society, Aleris Research and Development Fund, Eiken Chemical.

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