A population-based analysis of the incidence of early onset, invasive colon and rectal cancers during the periods covering 1995-1996 and 2014-2015 according to geographic location within the US and race/ethnicity showed that these diseases are increasing most rapidly among non-Hispanic whites in Western US states. The findings from this study were published in the Journal of the National Cancer Institute

The incidence of early onset (ie, colorectal cancer prior to the age of 50 years) is rising in the US. Although a number of risk factors for colorectal cancer have been identified and include obesity, heavy alcohol use, sedentary behavior, and smoking, etiologic factors contributing to the increased incidence of these diseases in younger people remain unclear. 

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The focus of this study was on investigating temporal trends in early onset colorectal cancer incidence for individuals aged 20 to 49 years during 1995-2015 in 47 US states and the District of Columbia (representing 95% of the US population) through an interrogation of the North American Association of Central Cancer Registries. 

These data were also analyzed according to racial/ethnic subgroup (ie, Hispanic, non-Hispanic black, and non-Hispanic white), as well as known risk factors for colorectal cancer. Data were combined for both sexes. 

A key finding from this study was a marked overall increase in the average annual percentage rate of early onset colorectal cancer in the US by 1.1% during the period covering 2006-2015 (0.7%/year and 1.7%/year for colon and rectal cancers, respectively), and these increases were most notable in Western states. 

For example, the incidence of invasive colorectal cancer increased from 6.7 residents of Washington state (per 100,000) during 1995-1996 to 11.5 residents per 100,000 during 2014-2015. Similarly, the corresponding rates for residents of Colorado were 6.0 and 9.5, respectively. Nevertheless, the incidence of early onset colorectal cancer was highest in Southern states and lowest in Western states.

An analysis according to racial/ethnic group showed that the incidence of early onset colorectal cancer was stable among Hispanics and blacks in many states, whereas the observed increased incidence in this disease was mostly limited to non-Hispanic whites, particularly those residing in Western states.

Interestingly, no association between obesity and alcohol use during 1995-2005 in the targeted age group and incidence of early onset colorectal cancer during 2006-2015 was observed. 

In commenting on these findings, the authors noted that “while lower colorectal cancer incidence in Western than Southern states likely reflects less obesity and physical inactivity, racial, and geographic differences in temporal trends are inconsistent with risk factor patterns. Obesity prevalence has risen nationwide, and more rapidly in blacks than in whites or Hispanics. The prevalence of smoking and heavy alcohol use among young adults is low and trends do not appear to explain the colorectal incidence trajectory.”

“Differences in the trend by subsite, race, and state implicate factors in addition to the ‘usual suspects’ and highlight the need for etiologic studies to explore early life colorectal carcinogenesis,” the study authors commented in their concluding remarks. 

Reference

Siegel RL, Medhanie GA, Fedewa SA, Jemal A. State variation in early-onset colorectal cancer in the United States, 1995-2015 [published online May 29, 2019]. J Natl Cancer Inst.  doi: 10.1093/jnci/djz098

This article originally appeared on Cancer Therapy Advisor