Screening Young Adults for Nonhereditary Colorectal Cancer

The public health burden of colorectal cancer is a significant challenge,withmorethan50 000deathsannually in theUnited States.Widespreadadoptionof theUSPreventativeTaskForce Guidelines for mandatory screening for colon cancer, along with improvement in access to advanced fiber optic technology and training of physicians, among other factors, are some of the reasons why the overall incidence of colorectal cancer has been decreasing in the United States and in other developed nations. Randomized trials andepidemiological studieshavedemonstrated significant decreases in the incidence and mortality from colorectal cancer with the use of colonoscopy (and flexible sigmoidoscopy), with the reduction of risk persistent even at 15 years after a negative colonoscopy finding.1,2 In the setting of these congratulatory reports of a successful public health screening program, this report from Bailey et al3 is rather unsettling. The authors examined the incidenceof colorectal cancer in9Surveillance,Epidemiology, and EndResults registries from 1975 to 2010 and describe a rather alarming trend of an increase in the incidences of colon and rectal cancers inyoungadults, especially in the20to-34-yearoldagegroup.This incidencewaspervasive regardlessof stage of disease, although not as dramatic in patients aged 35 to 49 years. Their data suggest an overall decrease in the ageadjusted incidenceof colorectal cancer,which couldbe attributed predominantly to the decrease in the incidence of all stages of cancer in the older population, although limitations in the use of all the registries could contribute to lack of generalizability.3 Temporal trends in incidence are rather difficult for clinicians to interpret given the changing technology and understanding/detection of disease. While it is possible that this increase in the incidence of cancer in young adults could be owing to increased detection from frequent use of colonoscopies in symptomatic young adults or to sophisticated pathological techniques/imaging, the simultaneous temporal decrease in the incidence of cancer in those older than 50 years is intriguing. One might argue that perhaps the risk reduction (or decrease in incidence) in this age group would have been higher had these temporal trends not been a factor. Nevertheless, assuming that this increasing incidence of colorectal cancer in young adults is a real phenomenon, it begs the question of why this is occurring and what one should do about it. The authors suggested the Western diet and lifestyle might be some of the contributing factors for this trend. Tumors occurring in younger patients are frequently different in their expression of microsatellite instability, BRAF, KRAS, or in the CpG island methylator phenotype and are more frequently mucinous and aggressive.2 Further epidemiological investigation into causality is critical to reduction in the nonhereditary cancer incidence in younger adults. While it is attractive to suggest that all adults should obtain a colonoscopy, especially given the possible durability of cancer risk reduction, it is important to note that the absolute incidence of colorectal cancer in the young adults (aged 20-34 years) is 1% of the total colorectal cancer burden and similarly fairly lowinthe35to49-year-oldagegroup(6.8%).Hence, Related article page 17 Research Original Investigation US Age-Related Incidence of Colon and Rectal Cancers