While the incidence of colorectal cancer (CRC) in people 50 years or older has declined, the incidence among people 20 to 49 years has increased, according to a report published online in JAMA Surgery.

CRC is the third most common cancer among men and women, with an estimated 142,820 new cases and an estimated 50,830 deaths in the United States in 2013.

From 1998 through 2006, the incidence of CRC declined 3 percent per year in men and 2.4 percent in women, a decrease largely attributed to an increase in screening, which is recommended for all adults over 50 years old.

However, incidence of CRC in adults younger than 50, for whom screening is not recommended, appears to be increasing and those patients are more likely to present with advanced disease, according to background information in the study.

Researcher Christina E. Bailey, M.D., M.S.C.I., of the University of Texas MD Anderson Cancer Center, Houston, and her co-authors analysed age disparities in trends in CRC incidence in the US.

The authors used data from the Surveillance, Epidemiology and End Results (SEER) CRC registry.

Data was obtained from the National Cancer Institute's SEER registry for all patients diagnosed with colon or rectal cancer from 1975 through 2010 (N=393,241).

The study results indicate that overall, the CRC incidence rate declined 0.92 percent between 1975 and 2010.

The CRC incidence rates declined overall by 1.03 percent in men and 0.91 percent in women.

The most pronounced decline was 1.15 percent in patients 75 years or older, while the rate for patients 50 to 74 years dropped 0.97percent.

However the CRC incidence rates increased for patients 20 to 49 years old, with the biggest increase of 1.99 percent in patients 20 to 34 years old.

The rate increased 0.41 percent in patients 35 to 49 years old.

The authors estimate that by 2020 and 2030, the incidence rate of colon cancer will increase by 37.8 percent and 90 percent, respectively, for patients 20 to 34 years old, while decreasing by 23.2 percent and 41.1 percent, respectively, for patients older than 50 years.

By 2020 and 2030, the incidence rates for rectosigmoid and rectal cancers are expected to increase by 49.7 percent and 124.2 percent, respectively, for patients 20 to 34 years old, while decreasing 23.2 percent and 41 percent, respectively, for patients older than 50 years, according to the results.

"The increasing incidence of CRC among young adults is concerning and highlights the need to investigate potential causes and external influences such as lack of screening and behavioural factors," the authors conclude.

Commentary: Screening Young Adults for Nonhereditary Colorectal Cancer

In a related commentary, Kiran K. Turaga, M.D., M.P.H., of the Medical College of Wisconsin, Milwaukee, writes: "In the setting of these congratulatory reports of a successful public health screening program, this report from Bailey et al is rather unsettling."

"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," Turaga continues.

"Hence, widespread application of colonoscopic screening might add significant cost and risk without societal benefit. However, this report should stimulate opportunities for development of better risk-prediction tools that might help us identify these individuals early and initiate better screening/prevention strategies. The use of stool DNA, genomic profiling and mathematical modeling might all be tools in the armamentarium of the oncologist in the near future," the author concludes.

Source: JAMA Surgery