Younger adults may have the highest risk of presenting with distant-stage colorectal cancer, according to researchers. A distant-stage cancer is one that has spread beyond adjacent organs or tissues.

Colorectal cancer, sometimes called colon cancer, occurs when cells in the colon or rectum grow out of control. 

In a study published this week in a journal by the American Association for Cancer Research, the authors analyzed annual incidence data in the U.S. SEER 18 cancer registry from the years 2000-2016, including 103,975 patients with colorectal adenocarcinoma. 

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Adenocarcinoma is a type of cancer that may occur almost anywhere in the body, starting in glands that line the insides of the organs, according to the Cancer Treatment Centers of America.

They divvied up the data by disease stage, subsite, patient age and race before calculating the change in incidence rate and change in distant-stage proportions – or the percentage of distant-stage disease out of all cancer stages combined – between 2000 and 2016 for various age groups. 

Those age groups include adults ages 20-29, 30–39, 40–49 and 50–54.

The researchers found that in comparing 2000-2002 with 2014-2016, the steepest percent increases are in distant-stage cancers. The steepest percent increase occurred for distant-stage colorectal adenocarcinomas and were most pronounced for younger age groups. 

Colon-only, distant adenocarcinoma increased most in people aged 30–39, with a 49% increase between 200 and 2016.

For rectal-only adenocarcinoma, distant-stage increases were steepest in 20-29-year-olds, with a 133% increase, followed by a 97% increase in individuals ages 30-39 and a 48% increase in 40-49-year-olds.

Additionally, corresponding decreases in the incidence of early-stage disease were observed among these subgroups.

The group also found that patients who were 20-29 years old had a 29% likelihood of presenting with distant disease, compared with 20% likelihood for 50-54-year-olds.

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Distant-stage colorectal adenocarcinoma proportions increased among young patients between the 2000-2002 and 2014-2016 time frames, with the greatest increases observed among 20-29-year-olds and 30-39-year-olds for rectal-only disease.

When analyzed by race, the largest increase in distant-stage rectal adenocarcinoma proportions from the 2000-2002 to 2014-2016 time frames occurred among 20-29-year-old non-Hispanic Black individuals, 20-29-year-old Hispanic individuals and 30-39-year-old non-Hispanic Black individuals.

Comparatively, for colon adenocarcinoma, distant-stage proportion increased most among 20-29-year-old non-Hispanic Black individuals.

"Youngest patients show greatest burdens of distant colorectal adenocarcinoma. Although affecting all races, burdens are higher in non-Hispanic Black and Hispanic subgroups, although case counts remain relatively low," the study reads.

A limitation of the study was the use of population-based data from the national registry, which did not include information about patients' family history or symptoms.

Author Jordan Karlitz, chief of the Gastrointestinal Division at Denver Health Medical Center and an associate professor at the University of Colorado School of Medicine, said in a release that understanding the trends and demographics of the rising rates could help to improve screening and early detection, as well as aid in targeting preventive measures to those with the highest risk.

The findings, he noted, highlight the importance of optimizing early detection and screening and Karlitz said he hoped the study would motivate people to get screened at age 45.

"However, many patients under age 45 will not be eligible for average-risk screening, so it is imperative that we stratify young individuals for early testing based on symptoms and family history," he added.

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Karlitz said additional focus should be placed on "racial subgroups that have an increased tendency to present with distant-stage disease, including the youngest non-Hispanic Black and Hispanic populations, to reverse these trends."

The author said further research is needed to understand risk factors.

The CDC shows, as of 2018, 52,163 people died of colon and rectum cancer, with 141,074 new cases reported. 

For every 100,000 people, 37 new colon and rectum cancer cases were reported and 13 people died of this cancer.