Similar rates of fecal immunochemical test (FIT) completion and colonoscopy yields were observed between adults aged 45 to 49 years and those aged 50 years in a new study published in Annals of Internal Medicine.

Among more than 267 000 participants who received a FIT kit in 2022, FIT completion within 3 months was slightly higher in those aged 45 to 49 years (38.9%) compared with those aged 50 years (37.5%).

“These findings support recent guideline recommendations to initiate CRC screening at age 45 years and can inform efforts to implement earlier FIT-based CRC screening,” co-first author Theodore R. Levin, MD, from the division of research at Kaiser Permanente Northern California, and colleagues wrote in the study published online October 22, 2024.

In recent years, the American Cancer Society, US Preventive Services Task Force, American College of Gastroenterology, and the US Multi-Society Task Force on Colorectal Cancer all shifted the recommended age to start CRC screening from 50 years to 45 years. According to researchers, the younger age threshold was based on evidence of rising disease burden in younger adults, emerging research demonstrating the prevalence of advance colorectal neoplasia in adults aged 45 to 49 years is approaching rates in those aged 50 to 59 years, and data from modeling studies showing that screening benefits outweigh the potential harms and costs.

“In issuing qualified recommendations for an earlier start to CRC screening, organizations have acknowledged that few data are available on screening completion and outcomes in people aged 45 to 49 years,” investigators wrote. “In response to the call to initiate earlier CRC screening, Kaiser Permanente implemented screening starting at age 45 years in most regions by offering mailed and office visit-based [FIT] kit distribution through organized CRC screening programs, in addition to opportunistic colonoscopy.”

In the current retrospective cohort study, Levin and colleagues investigated rates of FIT completion and coloscopy yield among 267 732 patients from Kaiser Permanente Northern California (80.7%), Washington (9.7%), and Colorado (9.5%) health systems. Participants were divided into 2 cohorts: aged 45 to 49 years (79.9%) and aged 50 years (20.1%), according to the study.

All patients received a FIT kit by mail or during an office visit from January to September 2022. Patients were excluded if they had previously received a FIT kit or underwent colonoscopy, so the FIT kits distributed in 2022 were the first documented CRC screening opportunity for each patient, investigators said.

The primary outcomes included FIT completion within 3 months of the distribution date; FIT positivity, defined as the proportion of completed FITs with a positive result; follow-up colonoscopy completion, defined as having a colonoscopy within 3 months of a positive FIT result; findings at the follow-up colonoscopy (ie, any adenoma, adenoma with advanced histology, CRC).

Women comprised 50.5% of the overall cohort and the distribution by race and ethnicity was 39.5% White, 22.3% Hispanic, 21.2% Asian, 4.6% Black, 0.4% American Indian or Alaska Native, and 1.1% Pacific Islander, according to the study.

FINDINGS

As previously stated, investigators observed that overall FIT completion across health systems was slightly higher in adults aged 45 to 49 years (38.9% vs 37.5%; adjusted risk ratio [aRR] 1.05, 95% CI 1.04-1.06). They reported similar results among men (37.3% vs 35.7%; aRR 1.06, 95% CI 1.04-1.08) and women (40.4% vs 39.4%; aRR 1.04, 95% CI 1.03-1.06) as well as Asian (47.7% vs 44.9%; aRR 1.07, 95% CI 1.04-1.09) and White (42.4% vs 40.4%; aRR 1.06, 95% CI 1.04-1.08) adults but not those of “other” race (28% vs 36.3%; aRR 0.78, 95% CI 0.62-0.97).

Researchers further noted adults aged 45 to 49 years at Kaiser Permanente Colorado were “substantially less likely” to complete FIT than those aged 50 years (30.7% vs 40.2%; aRR 0.77, 95% CI 0.73-0.8). Levin and colleagues noted this lower rate of completion “may be explained” by an electronic health records care gap which disproportionately referred younger patients for colonoscopy when FIT was not yet available to this population.

“Thus, those most interested in CRC screening may have opted for colonoscopy, leaving the FIT offering to those who were less likely to complete screening,” Levin and coauthors wrote.

Also, compared with individuals aged 50 years, the younger age group experienced decreased FIT positivity (3.6% vs 4.0%; aRR 0.91, 95% CI 0.84-0.98) and adenoma detection (58.8% vs 67.7%; aRR 0.88, 95% CI 0.83-0.95), but had similar rates of colonoscopy within 3 months following a positive FIT result (64.9% vs 67.4%; aRR 1.00, 95% CI 0.94-1.05). Yields for adenoma with advanced histology (13.2% vs 15.9%; aRR 0.86, 95% CI 0.69-1.07), polyp with high-grade dysplasia (3.4% vs 5.1%; aRR 0.68 95% CI 0.44-1.04), sessile serrated lesion (10.3% vs 11.7%; aRR 0.92, 95% CI 0.71-1.21), and CRC (2.8% vs 2.7%; aRR 1.10, 95% CI 0.62-1.96) were similar between groups.

The relatively short 3-month follow-up was a limitation of the study, Levin and colleagues stated. A longer follow-up would likely have resulted in higher completion rates and possibly more differences between the groups. Also, restricting the study to adults aged 45 to 50 years instead of including younger and older individuals may have limited their ability to find the inflection point for CRC risk.

"Finally, an assessment of the policy significance of these findings should take into account that the study was not specifically designed to directly compare the strategies of initiating CRC screening at age 45 versus 50 years," Levin et al concluded.

Reference: Levin TR, Jensen CD, Udaltsova N, et al. Colorectal cancer screening completion and yield in patients aged 45 to 50 years: An observational study. Ann Intern Med. Published online October 22, 2024. doi:10.7326/M24-0743