Early Colorectal Cancer Screening at Ages 40-49 Reduces Long-Term Incidence and Mortality
As the incidence of young-onset colorectal cancer continues to rise, the findings from a large Taiwanese population-based study support lowering the age for initial screening.
A large Taiwanese cohort study found that initiating fecal immunochemical test (FIT) screening in adults aged 40 to 49 years, rather than at the standard age of 50, significantly reduces colorectal cancer (CRC) incidence by 21% and mortality by 39% over nearly 2 decades of follow-up. Further, fewer FIT screenings were needed to prevent 1 case of CRC when screening began at the earlier age vs the standard age.1 Amidst the quickly rising rates of young-onset CRC, the addition of this large population-based study to the literature is timely.
The research, published in JAMA Oncology, addresses what has emerged as a critical gap in colorectal cancer prevention. Study authors cite data that show while screening programs for adults aged 50 to 75 years have successfully reduced CRC incidence and mortality, rates have paradoxically increased among younger adults, with the most significant rise in the 40 to 49 age group.2,3 Several organizations, including the US Preventive Services Task Force,4,5 have lowered their recommended screening age from 50 to 45 years.
However, the investigators, led by professor Tony Hsiu-Hsi Chen, of the Institute of Health Analytics and Statistics, College of Public Health, National Taiwan University, Taipei, Taiwan, emphasize that these recommendations relied primarily on extrapolation of modeling studies based on the older age group and not on empirical data from actual screening programs among the younger population.
For the population-based study, researchers analyzed data from 263,125 Taiwanese residents aged 40 to 49 years who participated in community-based screening programs in Keelung and Tainan between 2001 and 2009, before Taiwan's nationwide biennial screening program launched for individuals 50 and older in 2004. The team created 4 subcohorts based on participation patterns: those who underwent both early screening (ages 40-49) and regular screening (50+), early screening only, regular screening only, and no regular screening. Screening was accomplished using fecal immunochemical testing (FIT).
The investigators followed participants until 2019, comparing CRC incidence and mortality across groups. To address potential self-selection bias, they employed a delayed screening design and propensity score matching, restricting primary analyses to participants who attended regular screening after age 50. This approach compared individuals who started screening in their 40s with those who delayed until age 50, while both groups continued regular screening.
FINDINGS
Among 39,315 participants who underwent both early and regular screening, researchers observed a CRC incidence rate of 26.1 cases per 100,000 person-years compared with 42.6 cases per 100,000 person-years among 223,810 participants who underwent regular screening only. CRC mortality rates were 3.2 per 100,000 person-years in the early screening group versus 7.4 per 100,000 person-years in the regular screening group, with mean follow-up periods of 17.4 and 17.0 years, respectively.
In propensity score-matched analyses controlling for demographic factors and family history, early screening significantly reduced CRC incidence (adjusted relative risk [aRR], 0.79; 95% CI, 0.67-0.94) and mortality (aRR, 0.61; 95% CI, 0.38-0.98). An extended nonadherence adjustment applied to all subcohorts confirmed these findings, showing a 25% reduction in incidence (aRR, 0.75; 95% CI, 0.72-0.77) and 34% reduction in mortality (aRR, 0.66; 95% CI, 0.62-0.71).
The benefits appeared most pronounced in participants aged 50 to 64 years during follow-up, approximately 10 to 15 years after initial recruitment. This timing aligns with the lead time necessary for the long natural history of CRC, the authors pointed out. The number needed to screen to prevent one additional CRC case was 1,548 when screening began at ages 40-49, compared with 2,079 when screening began at age 50.
The authors acknowledge several limitations to their study, including that age- and sex-specific FIT cutoff values had not been established when early screening was introduced. In addition, cultural, genetic, dietary, and healthcare differences may affect generalizability to other populations beyond Taiwan.
The authors conclude that initiating FIT screening at ages 40 to 49 years significantly reduces long-term CRC incidence and mortality compared with standard screening beginning at age 50. "This was demonstrated using real-world data from a community-based early screening program that transitioned into a national screening initiative with a delayed screening design," they wrote.
These findings provide empirical support for current recommendations to lower the CRC screening initiation age, with substantial public health implications, the concluded.
