Early-Onset Colorectal Cancer: New Risk Factors or More of the Same at Earlier Ages?

Rates of colorectal cancer diagnosed before age 50 (early-onset colorectal cancer) are increasing in many countries. Many regions have lowered the age of screening initiation to 45 in response. Although early studies suggest increases in early cancer detection and improved outcomes among newly eligible individuals, some of the fastest increases are among those below 45, particularly for rectal cancers. In those below 45, population-wide screening is not likely to be cost-effective. Research to understand the factors driving the increases is essential in these younger groups. Recent data suggest that both novel and known exposures play a role. Novel initiators such as colibactin-producing Escherichia coli have been identified, and known promoters such as obesity, poor diet, and inactivity, among others, are increasing in prevalence among younger generations. Data from Baek and colleagues reinforce the role of metabolic and lifestyle factors, with differences observed between sexes. Their findings support the concept that early exposure to known promoters increases the risk of carcinogenesis. Future studies that incorporate biomarkers along with purposefully collected early-life data will be integral to identifying causal exposures and informing targeted cancer prevention strategies. See related article by Baek et al., p. 647.