# Screening outcomes at second FIT screening in individuals with a first time negative FIT‐result or low‐risk adenomas: Results from a nationwide FIT screening program

## TL;DR

People with low-risk adenomas detected during initial FIT screening have a higher short-term risk of colorectal cancer compared to those with negative FIT results, but they are less likely to return for follow-up screening.

## Contribution

This study is the first to compare cancer risk and screening participation rates between low-risk adenoma and FIT-negative groups in a nationwide FIT screening program.

## Key findings

- Low-risk adenoma participants had a higher incidence of interval CRC compared to FIT-negative participants.
- The FIT2 positivity rate was significantly higher in the low-risk group compared to the FIT-negative group.
- Low-risk participants had a higher detection rate of screen-detected CRC at the second FIT screening.

## Abstract

In Denmark, participants in faecal immunochemical test (FIT) screening with low‐risk adenomas are recommended a return to biennial FIT‐screening. However, they participate less than the FIT‐negative group (FIT1‐negative) at subsequent screening. Further, it is not clear how much this group benefits from the subsequent screening. We aimed at comparing the CRC incidence before and at the next screening (FIT2) in the low‐risk group to that of those having a FIT‐negative result at first time FIT‐screening. In this register‐based cohort study, we estimated the incidence of interval CRC (ICRC) and results of FIT2, including the FIT2‐positivity rate and rate of screen detected CRC (SDCRC). Relative risk (RR) comparing the low‐risk group to FIT1‐negatives was estimated. Adjustment for age and sex was performed with binary regression and presented with a 95% confidence interval (CI). Incidence of ICRC was 0.17% and 0.08% in the Low‐risk group and FIT1‐negative group, respectively, RR 2.18 (95%CI 1.51; 3.16). After adjustment, RR was 1.76 (95%CI: 1.22; 2.55). The FIT2‐positivity rate was 14.4% and 4.4% for the Low‐risk group and FIT1‐negative group, respectively. At FIT2‐screening, the detection of SDCRC was 0.36% and 0.16% in the low‐risk and FIT1‐negative group, respectively, RR 2.27 (95%CI: 1.46; 3.54), adjusted 1.83 (95% CI: 1.17; 2.85). Despite a recent colonoscopy, participants having low‐risk adenomas detected at first colonoscopy in FIT‐screening remain at a higher short‐term risk of ICRC and SDCRC compared to the FIT1‐negatives. Continuous participation in FIT‐screening is important for the Low‐risk group.

What's new?

Fecal immunochemical test (FIT) screening is increasingly common as a population‐based screening tool for colorectal cancer (CRC). If the follow‐up colonoscopy after a positive FIT detects only low‐risk adenomas, those participants are recommended to continue biennial screenings, the same as people with negative FIT results. Here, the authors compared outcomes of the low‐risk group with those among the FIT‐negative group. They found that people with low‐risk adenomas had a higher short term risk of cancer than those who had an initial negative FIT. However, low‐risk participants were less likely than FIT‐negative participants to return a second FIT, which may have slightly affected the results of second FIT outcomes.