COLONOSCOPY ADHERENCE IN A MULTI-CENTER STUDY OF COLORECTAL CANCER (CRC) SCREENING

Background: The Nordic-European Initiative on Colorectal Cancer (NordICC) Study highlighted the impact of adherence on the effectiveness of colonoscopy at reducing CRC incidence and mortality. Within a large, randomized trial comparing colonoscopy to fecal immunochemical testing (FIT) for average risk screening, we previously reported that adherence with annual FIT was initially high (81.6% in year 1) and falls to 59-68% in subsequent years (Gastroenterology 2022;172.7:S-199).

Aim: To determine screening colonoscopy participation and predictors of adherence.

Methods: Eligible participants were age 50-75 years, due for CRC screening and willing to be randomized to colonoscopy vs. FIT at 46 Veterans Affairs medical centers during 2012-2017. Those with first degree relatives with CRC or signs or symptoms of CRC were excluded. Stepwise logistic regression, stratified by site, with p<0.1 for inclusion and p<0.05 criteria for remaining in the multivariable model was used to identify independent associations with colonoscopy adherence at 6- and 12-months.

Results: Among 25,065 colonoscopy-arm participants (mean age 59.1 years), 93.2% were male, 69.8% were White, 24.0% were African American or Black (AA), 1.6% were Asian, 0.8% were American Indian or Alaska Native (AIAN), and 3.7% other race. Hispanic/Latino ethnicity was reported by 11.3%. Overall, 69.3% and 70.7% completed colonoscopy within 6 and 12 months, respectively. At 6 months, the odds of adherence were 12% lower for women vs. men, 15% lower for AA and 43% lower for AIAN vs. Whites, 2% lower per year of age and 29% lower for current vs. never smokers. (Table). The odds of adherence were most positively associated with having had a prior colonoscopy (45% increase) and with having a second degree relative with CRC (17% increase), college degree (16% increase), prior screening with occult blood testing (14% increase) and former smokers (7% increase). The evaluation of 12-month adherence revealed similar findings.

Conclusions: Though colonoscopy adherence (71% at 1 year) was lower than we previously reported for FIT (82% in the first round), it was substantially higher than the 42% reported in the largest randomized colonoscopy study to date (NordICC). Predictors of adherence were different than those we previously reported for FIT. Most notably, age was inversely associated with colonoscopy adherence but positively associated with FIT adherence. Also, FIT adherence was not associated with sex or having a second degree relative with CRC. Our work extends prior studies demonstrating the importance of individual-level factors in predicting screening adherence, including identification of differences by screening strategy. Interventions, especially for those with independent risk factors for non-adherence, are needed to improve screening participation.

*The first two authors are co-first authors.