Colorectal cancer screening with fecal immunochemical testing or primary colonoscopy: An analysis of health equity based on a randomised trial.

Background: We have addressed health equity attained by fecal immunochemical testing (FIT) and primary colonoscopy (PCOL), respectively, in the randomised controlled screening trial SCREESCO conducted in Sweden.

Methods: We analysed data on the individuals recruited between March 2014, and March 2020, within the study registered with ClinicalTrials.gov, NCT02078804. Swedish population registry data on educational level, household income, country of birth, and marital status were linked to each 60-year-old man and woman who had been randomised to two rounds of FIT 2 years apart ( = 60,123) or once-only PCOL ( = 30,390). Furthermore, we geo-coded each study individual to his/her residential area and assessed neighbourhood-level data on deprivation, proportion of non-Western immigrants, population density, and average distance to healthcare center for colonoscopy. We estimated adjusted associations of each covariate with the proportion to respective arms; ie, the preferred outcome for addressing health equity. In the FIT arm, the test uptake and the colonoscopy uptake among the test positives were considered as the secondary outcomes.

Findings: We found a marked socioeconomic gradient in the colonoscopy attendance proportion in the PCOL arm (adjusted odds ratio [95% credibility interval] between the groups categorised in the highest vs. lowest national quartile for household income: 2·20 [2·01-2·42]) in parallel with the gradient in the of the FIT × 2 screening (2·08 [1·96-2·20]). The corresponding gradient in the colonoscopy attendance proportion out of all invited to FIT was less pronounced (1·29 [1·16-1·42]), due to higher proportions of FIT positives in socioeconomically disadvantaged groups.

Interpretation: The unintended risk of exacerbating inequalities in health by organised colorectal cancer screening may be higher with a PCOL strategy than a FIT strategy, despite parallel socioeconomic gradients in uptake.

Funding: This work was supported by the Swedish Cancer Society under Grant 20 0719. CB and US provided economic support from the Swedish Research Council for Health, Working life, and Welfare under Grant 2020-00962.