Colorectal cancer (CRC) remains the second most common cause of cancer-related death in the United States. Although the past several decades have seen significantly greater emphasis on screening and disease prevention for CRC, it has also become increasingly apparent that the age profile and associated risks for this cancer are rapidly changing.
Evidence of this can be found in recently released CRC statistics from the American Cancer Society, which are updated every 3 years using population-based cancer registries.
The incidence in CRC has shown a progressive decline over the past 4 decades. However, whereas in the 2000s there was an average decline of approximately 3%-4% annually, it slowed to 1% per year between 2011 and 2019. This effect is in part because of the trends among younger individuals (< 55 years), in whom the incidence of CRC has increased by 9% over the past 25 years.
The incidence of regional-stage disease also increased by 2%-3% per year for those younger than 65 years, with an additional increase in the incidence of more advanced/distant disease by 0.5%-3% per year. The latter finding represents a reversal of earlier trends observed for staged disease in the decade from 1995 to 2005.
These recent statistics reveal other notable changes that occurred in parallel with the increased incidence of younger-onset CRC. There was a significant shift to left-sided tumors, with a 4% increase in rectal cancers in the decades spanning 1995–2019.
Although the overall mortality declined 2% from 2011 to 2020, the reverse was seen in patients younger than 50 years, in whom there was an increase by 0.5%-3% annually.
Available incidence and mortality data for the current year are understandably lacking, as there is a 2- to 4-year lag for data collection and assimilation, and there have also been methodological changes for tracking and projections. Nonetheless, 2023 projections estimate that there will be 153,020 new cases in the United States, with 19,550 (13%) to occur in those younger than 50 years and 33% in those aged 50-64 years. Overall, 43% of cases are projected to occur in those aged 45-49 years, which is noteworthy given that these ages are now included in the most current CRC screening recommendations.
Further underscoring the risks posed by earlier-onset trends is the projection of 52,550 CRC-related deaths in 2023, with 7% estimated to occur in those younger than 50 years.
What’s behind the trend toward younger onset?
The specific factors contributing to increasing rates of CRC in younger individuals are not well known, but there are several plausible explanations. Notable possible contributing factors reported in the literature include obesity, smoking, alcohol, diet, and microbial changes, among other demographic variables. Exposure to high-fructose corn syrup, sugar-sweetened beverages, and processed meats has also recently received attention as contributing dietary risk factors.
The shifting trends toward the onset of CRC among younger patients are now clearly established, with approximately 20% of new cases occurring in those in their early 50s or younger and a higher rate of left-sided tumor development. Unfortunately, these shifts are also associated with a more advanced stage of disease.
There are unique clinical challenges when it comes to identifying younger-onset CRC. A low level of suspicion among primary care providers that their younger patients may have CRC can result in delays in their receiving clinically appropriate diagnostic testing (particularly for overt or occult bleeding/iron deficiency). Younger patients may also be less likely to know about or adhere to new recommendations that they undergo screening.
The landscape for age-related CRC is changing. Although there are many obstacles for implementing new practices, these recent findings from the ACS also highlight a clear path for improvement.
David A. Johnson, MD, is professor of medicine and chief of gastroenterology at Eastern Virginia Medical School, Norfolk, and a past president of the American College of Gastroenterology.
A version of this article first appeared on Medscape.com.