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A new analysis provided “strong” support for starting fecal immunochemical test (FIT) screening at ages 40-49 rather than at the currently recommended age of 50.

An exploratory initiative that offered FIT screening to residents aged 40-49 years in two Taiwan municipalities gave researchers an opportunity to test whether early screening made a real difference in colorectal cancer (CRC) mortality and incidence. They found that it did.

Both outcomes were “significantly lowered” with early screening compared with regular screening (starting at age 50), the authors found. Those who underwent early screening had lower CRC incidence (26.1 vs 42.6 per 100,000 person-years) and mortality (3.2 vs 7.4 per 100,000 person-years), with similar results after propensity score-matched analyses and in an extended nonadherence adjustment model.

The study was published online in JAMA Oncology.

Both Early and Regular Screening Are Best

Researchers analyzed a community-based FIT screening cohort of more than 500,000 Taiwanese residents aged 40-49 years between 2001 and 2009 who also then had an opportunity to undergo regular screening at age 50 or older.

Participants were categorized into four subcohorts based on early FIT screening at ages 40-49 and regular CRC screening at 50 years or older: Those who underwent both early and regular screening, those who underwent only early screening, those who underwent only regular screening, and those who refused regular screening.

Participants were followed up until 2019 to compare CRC incidence and mortality across subcohorts. To reduce self-selection bias, a delayed screening design and propensity score matching were used, restricting analyses to participants who underwent regular screening.

Of the 263,125 included participants, 55.8% were women. A total of 39,315 participated in early and regular screening, whereas 223,810 participated in only regular screening.

The early screening group had lower CRC incidence (26.1 vs 42.6 per 100,000 person-years) and mortality (3.2 vs 7.4 per 100,000 person-years).

In propensity score-matched analyses, early screening significantly reduced CRC incidence (adjusted relative risk [aRR], 0.79) and mortality (aRR, 0.61).

The findings persisted in an extended nonadherence adjustment model across all four subcohorts, showing a 25% reduction in incidence (aRR, 0.75) and a 34% reduction in mortality (aRR, 0.661).

The authors noted that CRC incidence and mortality were lower for the group participating in both early and regular screening than for the group participating in only regular screening. “This difference was particularly evident in the three key age groups — age 50-54 years, 55-59 years, and 60-64 years — who derived the greatest benefit from early-age screening during follow-up (approximately 10-15 years after recruitment at age 40-49 years),” the authors wrote.

Furthermore, the findings showed that FIT screening at ages 40-49 required fewer tests to prevent one CRC case than regular screening and was therefore cost-effective.

However, the authors concluded, “whether early screening policies are generalizable to other populations should be evaluated carefully.”

‘Essential’ to Inform Practice

In a related editorial, Thejus Jayakrishnan, MD, of the Dana-Farber Cancer Institute, Harvard Medical School, Boston, and colleagues noted that the authors had limited information on established CRC risk factors in the study population or on the proportion of individuals in each group who tested positive on FIT and who subsequently followed through with a colonoscopy, factors that could affect outcomes.

Nevertheless, they wrote, “This analysis adds to the current limited body of literature — comprised mainly of observational studies, colonoscopy registry studies, and modeling studies — that suggests that initiating screening at an age younger than 50 may lead to public health benefits. Until randomized clinical trials are conducted and results available, observational studies such as this will be essential to inform policy and practice,” although external validation of the findings in different countries is needed.

The study was supported by the Health Promotion Administration, Ministry of Health and Welfare of the Taiwanese government. Lead author Han-Mo Chiu, MD, PhD, National Taiwan University, Taipei, Taiwan, reported receiving grants from the Taiwanese government during the conduct of the study, as well as personal fees from Boston Scientific, Olympus Medical, and Fujifilm Medical System outside the submitted work. No other disclosures were reported.

Two coauthors of the editorial declared receiving personal fees and grants from commercial entities outside the submitted work.

Marilynn Larkin, MA, is an award-winning medical writer and editor whose work has appeared in numerous publications, including Medscape Medical News and its sister publication MDedge, The Lancet (where she was a contributing editor), and Reuters Health.